Technology – Tales On Two Wheels

How To Build a Mid Drive Ebike That Doesn’t Break

No wearing-out of the drivetrain early. No broken chains. No motor shifting…
No whining. Read this so you don’t become That Guy on the internet.

This article is the follow-up to How To Ride a Mid Drive Ebike Without Breaking It. That article points out how most of the online tantrums about unreliable mid drive ebikes are bad riding, not bad equipment.

This article’s main points are all found in different posts here on this site, and together, here and there, they all cover the ground I am re-covering here. However, this subject comes up so often I decided to try and consolidate things into one place.

I am not trying to list every single thing you need to do to build a bike (I don’t mention tightening all the bolts or putting air in the tires, for example). I’m trying to shine a light on the more common mistakes. Don’t make them and you stand a good chance of having a trouble-free bike. Some of this stuff is pricey, so maybe you’ll want to work it in bit by bit as budget permits.

Remember: a successful DIY mid drive is about both building and riding optimally. Mid drives – particularly the ones made for USA-legal and adventurous, off road DIY builders – up the ante on the required competence of both builder and rider. There is no way around this. If you want idiot-proof and simple do a hub kit. If you want the versatility that comes with a mid drive, though, you need to put in the extra time and effort.

I’ll focus solely on the mechanical bits this time, and break the process down into key component areas. We’ll start with:

Pick a Frame…

To get a mid drive to work properly, you need to pick a frame that can handle it, and this is not a given. Lots of frames are a bad choice. So what are we looking for?

… That Handles The Torque

I can still remember looking down at my very first mid drive build, a 4kw Cyclone, and saw the motor flex when I hit the throttle. With that flex, the whole bottom bracket flexed with it.

Thats a bad thing. Pick a frame of very sturdy construction. You are going to have an electric motor giving one hell of a pull on a chain that is connected to your back hub. That pull can flex the entire bike frame.

Can your typical mountain bike do it? Yes. Can your road bike with Columbus tubing from the 1980’s do it? Ehhhh lets say no on that one. Whats the problem? Designed for light weight and strength keyed to relatively smooth roads and human power, the stays are too spindly. All that power can pretzel the poor, innocent chainstays and seatstays when the power of ten pro riders yank on the chain.

How do you fix that? A lighter-duty BBS02 with the amp output dialed down is one solution I have seen done successfully several times. The lower amps do not yank on the chain hard. Some effort on the builder’s part to change the settings so pedal assist is kind and gentle is also important (and also preserves an authentic cycling experience).

… That Fits The Motor

Modern downtubes on mountain bikes tend to be curved and swoopy, coming into the bottom bracket at an arc that equates to a roughly 3-o’clock position. That arc means an installed external motor like a BBSxx has no choice but to hang straight down. Kiss goodbye your ground clearance. Here’s a picture of my 2018 Guerrilla Gravity Smash:

Take a look at how the down tube is curved, and how, on the right image where the drivetrain has been removed, its clear the only way to put a BBSxx-style motor on a bike like this will result in that motor hanging straight down.

You can see, sitting on the floor in that right picture, a Cyc X1 Pro motor, which has long arms that mount the motor as far forward as possible to avoid this ‘angle of the dangle’ problem.

How did I do in terms of mounting the motor and preserving ground clearance? Well, look above at the final installation. Look how low the chainring is. Draw an imaginary horizontal line parallel to the ground from that chainring… the motor is above that line.

The higher the better, but bottom line here is the motor is above the drivetrain so we haven’t lost a lot of ground clearance on this frame by using it (with the right mounting kit a Tangent Ascent motor will fit inside the triangle, just under the shock). So, this frame that is totally unsuited to one kind of motor can be pretty well suited to another.

Here’s another example frame. This is the type of frame typically recommended for a BBSHD, BBS02 or similar motor:

The down tube of this frame is straight as an arrow and attaches to the bottom bracket at a high angle. This allows you to rotate a dangly motor like a BBSHD up as far as possible so you lose as little ground clearance as possible. How did this shake out once this bike was built?

It came out pretty good. Bearing in mind this bike used a smaller-than-usual 40T chainring, the motor is roughly at the same height above the ground as the chainring. Maybe just a bit below. This is as good of a fit as you can expect on a bike for this kind of motor.

So… the lesson here is to think through your motor choice if you already have a frame to work with. Or the reverse if you have a motor on the shelf that needs a frame.

… That offers Good Chain / Crankarm Alignment

This is a tough one to nail down in advance. On chain alignment, you can come close during frame selection but you’ll never know for sure until you actually fit a motor into the frame, along with an assembled rear wheel so you can drape the chain and figure out how it lays.

As to crankarm alignment… thats one you will have to work out once you have a bike on a stand during the build. The key is to remember that your desired final result is to align the pedals directly underneath you… not the crankarms. Focusing on the pedals gives you a couple of extra options over and above finding an offset pair of arms to even things up. I have used uneven-width pedal spacers for some big changes, and different washer counts on one side or the other (from zero up to two) to move the pedals an additional 1.5mm to 3mm in either direction.

uh oh… lots of extra space on the drive side. Can’t use standard crankarms on this bike

I covered these issues in excruciating detail in How to Build an Ebike From Scratch: Tinkering. So I’m going to link you to that page and stop, rather than going through it all over again.

Buy The Right Drivetrain Parts

So very many builds fall on their face because the builder left cheap parts on the bike rather than replacing with strong ones.

Chainring

Here is another topic already done to death elsewhere. The options laid out here result in significantly different chain alignments. This is a pretty good general resource on the subject:

Musical Chainrings

Generally speaking for BBSxx style motors with a large secondary housing located where the chainring ordinarily resides, you want a chainring with an inward offset that helps with chain alignment.

You also don’t want to overdo the size of the ring. Generally, “smaller is better” thanks to the rules that go along with riding a mid drive ebike (See below). You don’t want to pick a big ring unless you know exactly what you are doing with regard to gear selection and chainline. 42T is typically considered ideal unless you are riding singletrack. You go as small as you can get away with in that case.

Do a little shopping and you’ll find quality offset chainrings from the usual big name players aren’t cheap. Especially post-COVID. Here’s a new one I found recently on Amazon that offers about 15mm of offset and is well constructed. The offset looks to be more than that simply because the alloy used in construction is so thick.

I bought this ring and it appears a solid alternative – with a great tooth profile – for about half the cost of the other high end rings.

Chain

A beefed up chain is often overlooked and just as often results in an Epic Fail. You can’t run a powerful mid drive and expect to use the cheapo chain you already have on your bike. Whatever you do, don’t use a cosmetic (painted) pretty chain, or one of those pricey skeletonized weight-weenie chains. Instead, spring the bucks and buy a proper strong chain.

I run 11-speed systems with a KMC e11 chain – the KMC ‘e’ line is specifically designed to take a mid drive’s punishment. These 11s chains are brutally expensive (today’s price is over US$47), but this is part of the cost of admission if you want to run 11s and a high powered motor that doesn’t snap chains (or wear them out really fast). 11-speed is a wonderful thing to have on an ebike – particularly on a bike you pedal instead of throttling – but the cost of durable 11s drivetrain parts is a serious deterrent.

The story gets a lot better if you are using an 8, 9 or 10-speed setup. The SRAM EX1 ebike chain is used for their (hideously expensive) 8-speed EX1 mid drive-stressed drivetrain system. Here’s the thing though: That chain has an MSRP of US$28, and is usually sold for about US$25. The link above to Amazon has it on sale right now for US$18.95.

It gets better still: The EX1 system is 8-speed, but the chain is sized for a 10-speed system. That means you can use this chain on 8-, 9- and 10-speed drivetrains. Since 9s is probably the ideal sweet spot for mid drives, this chain can be considered almost everyone’s inexpensive default. To sweeten the deal, the chain comes with 144 links. So it will fit everything but a longtail without having to buy and section two chains together.

Rear Derailleur

This one is quasi-optional. A quality derailleur is always a good thing. Especially if your alternative is something like a cheapie Tourney or similar.

11 Speed

I use a SRAM GX 2.1 long cage rear derailleur. This is not meant for a 1x drivetrain but if you just use a narrow-wide front chainring, you’re fine. At over US$100 a pop this is not a low cost option, and one more reason why you need to know you want more gears and more finely-diced cadence options to bother with 11-speed.

9 Speed

I have found two I consider to be stars:

Box Components Prime 9
I have two bikes with these, including my most recent build: The Apostate. My preferred version is the Box Two Prime 9 Extra Wide, coupled to their Box One single shifter, which is tailored for ebike use. The Extra Wide part refers to extra wide range on the rear cluster, which in English means Big. You can go up to I believe a 50T rear cluster with one of these. Combined, shifter-plus-derailleur is about a US$185 solution. I like it better as a premium option because… it shifts spot-on, was super easy to initially adjust and runs silky smooth.

Microshift Advent
I like the Long Cage version, which runs US$60 and is meant for 2x systems but works fine on 1x. The Pro shifter is single-shift like the Box, and costs a whopping US$29. This setup is significantly cheaper than the Box. It works just a little less slick, and the fit/finish is more… workmanlike… but its nothing to complain about given the price range its in.

I have to say I like the adjustable clutch on the Advent better than anything else I have ever used.

Shifters

I have mentioned but not explained why single-shift is needed for a mid-drive so here goes: Shifting under power is a Very Bad Thing. If you shift a bunch of gears at once, as is easily possible with a standard trigger shifter, its Way More Bad. If you are trying to snap your chain as quickly as possible (or taco a chainring or cog), thats how you do it. Single-shift shifters only allow one gear shift per trigger pull, so you can’t screw up. So either learn to carefully shift one gear at a time (certainly you can do that, as I do on my older bikes) or buy something that eliminates the issue.

This looks like a good time to link to the discussion of whether or not you want to install a gear sensor. Spoiler alert: I don’t use them and I still stay safe.

Rear Cluster

Put simply, you want durability. Forget about light weight. You want all-steel cogs, preferably pinned together into a monolithic block. That block distributes the force across the cassette body/freehub underneath so you don’t dig a trench into the poor thing when you hit it with a shipload of watts.

11-speed
The Sunrace CSMS7 is an all-steel 11-42T cluster, pinned together. I haven’t found anything else that is all-steel in an 11-speed. These clusters are often tough to find in stock and there’s no telling how long the link above will remain valid.

The CSMS7. Steel spiders, steel cogs and permanently pinned together. Wunderbar.

9-speed
For bikes that don’t require a lot of range, you can’t beat the Shimano HG400-9. They are found in a range of tooth counts – my favorite is the coated 12-36T. They are dirt cheap and functional. All steel except the smallest cogs, and pinned together. Nearly indestructible and easy on the cassette body.

The Microshift Advent 11-46T Hardened Steel cluster is my absolute favorite. A nice wide range up top. No spiders (each cog is 1-piece). Pins are all over the place to hold it together and prevent any torque tacos.

And its cheap with a US$35.99 price at the time of this writing. Unbeatable for a 9-speed mid drive build.

Rear Cassette Body (Freehub)

Whatever it is, it needs to be steel. If not, with an unrestricted DIY mid drive you’ll dig into it like its made of cheese. This is a big deal. I’m only devoting a couple of sentences to it, but thats because there’s just not that much to say. If you want to avoid tearing up this rather expensive and possibly difficult to replace part, use one made of steel. Period.

Left: Alloy at 1300 miles (and an AWD bike so it had an easy life). Right: Steel replacement. A year later I checked the steelie and it wasn’t even scratched.

Rear Hub

With all the talk above of strong chains, steel cogs and steel clusters, you can see where this is going I bet. With all that durable hardware we are reinforcing the drivetrain further and further down the line until we find the next failure point. After we get to the surface of the cassette, the next thing that breaks are the pawls inside the freehub. Whats a pawl? Here are a couple of pictures where they are visible:

The little things sticking out on the end are ‘pawls’: ratcheting couplers that hold the hub firmly while you and your motor apply force to the rear thru the chain. If they give out, the chain ‘freewheels forward’ and you lose the ability to apply force to the rear wheel to make it go. Mid drives putting out big power put big stress on these poor little pawls, and they can die as a result.

Its not hard to see why. All torque is transmitted through those pawls. What you need is more points of engagement. You can find 4, 5 and even 6-pawl freehubs. You can also buy quality rear hubs that can take this level of abuse (I hear Salsa makes some, as do Sun Ringle). You can also change the game and go to a different kind of mechanism that is effectively indestructible to a mid drive…

Hooray for a ratchet engagement mechanism

Bike Radar did a good piece on freehub construction so I’ll just link to that article here and let you read the details, and the comparison of pawl vs. ratchet. So far as I can tell across several wheelsets and several thousand miles, the DT 350 hubs with standard 18T and 24T ‘Hybrid’ ratchet mechanisms are effectively indestructible.

Rear Wheel

So we’re walking the points of failure back still. ‘Under’ the inside of the cassette mechanism is the hub, spokes and the rim itself.

This is not something anyone wants to hear, but if you want a trouble-free mid drive you put on a quality wheel built for it, by someone who knows what they are doing. This is not cheap, hence the reason nobody wants to hear it. And you may be able to do without. Heck… a lot of Mongoose Dolomite conversions are out there and running just fine. But if you expect to pour on the miles and keep doing so for years, trouble-free. Well, your money will be well-spent on a beefy wheel.

Lets take a typical 26″ example. I really like the SunRingle MTX39. It comes in 32- and 36-hole versions. At US$60-90 each they are not cheap, but also not crazy-expensive, either. Its ridiculously strong, but isn’t light weight.

My MTX39 on the rear of my Bullitt. I also use them on my Envoy.

If I want to blow off the budget and go for strong, lightweight (and tubeless) a DT Swiss FR-560 is a winner. I have them on 26″ and 29″ wheels, and they are also available in 27.5. But at about US$150 a pop you have to want em pretty bad.

Next, what about the spokes? Choose good, strong ones. Sapim Strongs are an excellent choice. So are DT Swiss Champions, or DT Competitions. If you are made of money, DT Alpines are pretty awesome, too. These spokes as a body are not the great big 12-gauge spokes you see on some imported Asian rims. the European manufacturers substitute quality materials and smarter engineering and don’t need that massive construction, but they still provide superior strength.

And lets not forget the nipples! Spoke nipples that is. Once again, choose strong ones, not light ones. That means no alloy. Use the brass ones.

Don’t Ride Like a Dumbass

Build it as smart as you want, but if you do bad things you will get bad results.

How To Ride a Mid Drive Ebike Without Breaking It

So last but not least, follow that link. And don’t be a …

Range Anxiety? Be Prepared (and Stop Worrying)

Want to take a long trip with an ebike? Just want to proof yourself against running out of juice on your commute? Here are a variety of solutions.

I’ve put rather a lot of effort into proofing myself against running out of battery juice. In all the years I have been using an ebike as a daily driver – almost always for utility rather than for recreation – I have never run out of battery power. Even when I’ve forgotten to charge before a ride (more on that below).

There Are Solutions

Lets explore some range-extension options. Hopefully you’ll come across something here you hadn’t thought of and can take advantage of.

Use a Big Battery

This is the most obvious one. If you don’t want to run out of gas, put in a big gas tank. This is not a new idea. Nowadays when a gearhead hears about a Corvette Z06, a super fast, light and powerful version of that car comes to mind… but back in 1963, if your option code was RPO Z06, that meant you had the “big tank” Corvette… with a freaking 36 gallon gas tank to minimize refueling stops during races. Or Cannonball runs.

So not a new idea.

If you are doing a DIY ebike conversion, unless you have specific weight goals, you typically want to fit the biggest battery you can afford. Same goes for a manufactured ebike. If it has a larger battery option… you want that. Whether you can take advantage of an option will boil down to the size of your wallet. An XL-sized battery will also let you preserve your battery by charging it to 80% or 90%, but thanks to it being oversized you still have enough in the tank to go wherever you please.

I am all about big batteries on the bikes I build. The Great Pumpkin has a 31 amp-hour, 52 volt custom triangle pack. The Lizzard King has a 32ah/52v brick hiding under its floor. That ties for biggest pack in the fleet with 2Fat – now a recreational bike, it needs big power to run through remote stretches of beach without inland access. That bike has two parallel’d 16ah/52v packs joined together to make a single 32ah battery.

Bigger is better only up to a point. Big batteries equal big weight. So there’s a limit to what you can and should get away with. You can’t go this big on normal neighborhood ebikes, nor should you.

With all that said, going big on a battery can also save your bacon when you do something like forget to charge your battery… there’s enough extra capacity to eke out a ride home rather than having to figure out a way to sleep over at the office.

Bring Along a Spare Battery

This is my least favorite solution, but it may work for you. If you have a battery, buy another one just like it and toss it into a backpack or pannier. Swap it in when needed. This is probably most likely going to appeal to folks with a manufactured ebike and thus no other options. Unfortunately with a solution like this, you can’t get anywhere near as much out of two batteries as you would be able to for a big single one, or for two joined together in parallel (you can to only partially drain each of your packs, hence the loss in capacity). But you suffer the same weight penalty.

Sidebar:
Don’t parallel batteries together unless you know EXACTLY what you are doing. Running packs in parallel increases the potential for danger dramatically, and should only be messed with by folks with the experience to know how to mitigate those increased risks.

Onboard Charging (Permanent Mount)

I have written up my experiences with using Mean Well power supplies as CC+CV ‘smart chargers’, and mentioned they are fanless and weatherproof. This and the fact they have mounting tabs means they can be mounted permanently. Assuming the bike is large enough to have a brick bolted on without anyone really noticing. That can mean cargo bikes and any bike with a front rack – the charger works great as a rack deck. And on the front, you don’t really miss the fact you can’t put a rack trunk on.

Pictured above on the left: The Big Fat Dummy and its 185w/3a charger gassing up at the park. The charger is bolted onto the lower deck, up front on the rack. On the right: The Great Pumpkin‘s 320w charger on the front rack is good for 5 amps.

The 480w monster now on the front rack of 2Fat is good for a whopping 8 amps. Its supersized, as when I need a recharge on that bike I am in the middle of nowhere and facing darkness, fog … and may need to negotiate with an unpleasantly high tide if I dawdle.

Onboard Charging (Carried in a Bag)

You don’t always want to be lugging a charger around; nor do you always have a place to bolt one on. I have both 185w and 320w portables that I bring along occasionally on bikes that don’t have a permanent charger mount. For instance, I didn’t want to add a heat-generating charger to the largely enclosed basement battery box on The Lizzard King. So I carry the 320w unit you see below when circumstances warrant (not the shoe. Thats just there for size comparison). Being able to pump in 5a into any battery is going to add a whole lot of range if you plug in while having lunch.

Speaking of open outlets, where are they best found? Here in the USA I have really good luck with public parks. Oftentimes a picnic canopy will have a working power outlet. You can also stop at a roadside cafe, shop or gas station and ask the owner if you can plug in while you are there visiting. This works best if you are stopping somewhere for lunch and will be there for awhile. I’ve also found plugs attached to the outside of restroom buildings at state parks.

Obviously, this approach works best on regular routes where you can determine in advance what is available. Keep your eyes open, scope out your options and file that information away for the time when you need to use it.

I include a ‘Y’ plug in my kit so if I am asking someone to plug into their AC power, I am proposing to share it, not take it over.

Don’t Be Such a Pig

This next one is obvious… or is it? Its a technique I have used and it gets the job done so here goes:

Use less power, as in dial back the assist. My Bullitt with its Great Big Battery was about 3 miles into a 16 mile Saturday morning Costco run when I realized I had forgotten to charge it after work on Friday. Its 52v/14S battery reads 58v when its full, and was already down to 52v when I realized my mistake. Not only would I be blowing my morning turning around and going back home, it would be hours before that battery was charged. I decided to just go for it. So I reduced my assist to the minimum and continued. When I returned home with a cartful of groceries stuffed into my cargo box and panniers, I was down into the mid 40’s, voltage-wise – and more than a little worn out.

But I made it. I wouldn’t have if I had not gone overboard with the size of the battery.

After this I made sure I carried a charger with me on these trips. There is a park midway on the journey with a publicly available power plug. I can plug in, sack out and catch a nap next to a water fountain and be on my way. Late… but I’ll have beaten the system.

Charge at Public (J1772) EV Charging Stations

Yes really. It may be difficult to find an open plain vanilla AC power outlet that you can use… but nowadays electric vehicle (as in automobile) charging stations are popping up all over the place.

If you do not live in the USA, you will want to find a different adapter than what I am describing below (from what I hear non-USA charging stations in the EU are much more likely to have an ordinary, separate outlet available for public use).

But in the Land of the Free, this may be the only obviously available power plug you can get hold of. I’m seeing them increasingly in parks and ordinary store parking lots. Likely they are also springing up at the more refined campsites and national parks.

This is my J1772–> Nema 5-20 adapter for plugging into an EV charger

This is an option that hasn’t been available until recently, and is still not widely known or even understood. Above is a picture of the adapter I have. It plugs into a USA-standard J1772 EV charger plug and terminates in a female NEMA 5-20 plug on the other side. NEMA 5-20 plugs are also compatible with NEMA 5-15 plugs. Folks in the USA know of the 5-15 as your garden variety 3-prong grounded electrical plug. Using this adapter, you now have a bridge directly from a 240v EV car charger to a plug that you can connect your charger into.

Fzzzzzzzz… BOOM!

Thats what could happen if you just plug in without making sure your charger can handle 240 volts of current versus the usual 120.

Here’s the thing: Many ebike chargers are manufactured to run on global power grid voltage. In the USA, we use 120v. Much of the rest of the world uses a lot more volts. 240v in particular. So if you are manufacturing chargers and want to sell them everywhere, you make one that can handle the various voltages right out of the box, so you only have to make one model. However, you can’t count on this feature being there. So check first.

How can you tell? Look at the fine print on the label. The really tiny print that you never read. In the case of the Mean Wells I use, its written clearly in big letters, since they are meant for commercial use and nobody cares if they look pretty.

Yup it’ll handle 240 volts, alright. Since I have also made chargers for relatives who use them on their ebikes in the EU, I know they work just fine on the higher EU voltages.

But thats me. YOU have to figure this out for yourself on your own charger. You won’t know until you go look.

So Much For The Good News…

Here comes the bad news: These adapters are expensive. I have seen them selling for as much as $200. Oddly enough, after some googling I found a seller only an hour or so down the road from me who seems to have the lowest sale price on the web. I paid $85 for mine. Thats still a lot. Lets hope the price is only going down as these types of units become more common.

Or better yet, lets hope that EV charging stations in the USA start commonly having normal AC plugs available.

Whether that happens or not, you should be able to do one or more of the things above, and turn range anxiety into something you used to have … but don’t anymore.

How To: Safe, Reliable Electrical Crimp Connections (part 2 of 2)

in Part 1 we introduced the topic and assembled our tools. This time, we’ll use them to make something and show how its done, step by step.

So after having gone through Part 1, we assembled our gear and have what we need to get a job done.

What are we going to do? I have an article on how to create an ultra reliable ebike battery charger (which also works as an AC charging brick for a solar generator like a Bluetti AC200P). Since I have an extra one sitting and gathering dust, we’ll make some plugs for it here. That will serve the dual purpose of giving readers of that other article a step-by-step construction guide.

What do we need to get the job done?

Everything we saw listed in Part 1. Our project device will be a Mean Well HLG320H-54A LED power supply.

The Mean Well power supply with bare wires. If purchased new retail, both ends will be stripped and tinned.

We will also need a 6-foot-long, 3-prong AC power cord with an open pigtail on the female side. Never seen one before? Don’t worry they are commonly available. Apparently a lot of construction workers tear up the cords on their power tools, so replacements are easy to find and cheap.

Lets get started.

Step 1

Size the heat shrink you will need at the very end of this process, and run it down along the wire NOW before you need it. I cannot even begin to count the number of times I have gotten wrapped up in making a cable and then realized I forgot to size and place the heatshrink for that last step. Do it now before you need to do it and before a connector is on and its too late.

The heat shrink has been added – nice and long – and you can slide it well back from the connection as needed.

Put it on the side that you can slide the furthest away from the heat gun for when we have to take that step later. You don’t want to be shrinking this one up when its out of position so it needs to be away from the heat.

Step 2

The wires on the pigtail side of the power cord are already stripped and tinned so they are easy to work with. Lets use those to teach ourselves how deep the butt end connectors are. We can trim these wires so their insulation fits right up to the edge of the metal connector insert. Once we do that, we’ll know how much we need to strip off the wires on the other side of this connection.

Dip the wire into the connector. The insulation on your wire should seat against the metal butt end connector inside. How much extra is there? Snip some off so the insulation fits right up to the end. Repeat for all three wires on the power cord.

Step 3

Next, we strip the wires that go into the other end of these butt-end connectors. The lengths we snipped down to in Step 2 give us an easy visual guide to how much we need to strip back on these wires.

A note on wire stripping: There can be a little more to it than just picking the hole that matches your wire gauge and biting in. I like to spend a little more time on the job so I don’t lose a single wire in the bundle (if I can help it).

Here’s the way I did this particular wire: I picked the 18 ga slot and was able to clamp down hard on it without damaging the wire underneath the insulation. Its a size up from where I’d get a clean, complete cut, and gave me a safe cut of maybe 80% of the insulation. Then I shifted down a size to the 20 ga slot and – very gently, clamped down on the same spot. Just a bit. While slowly spinning the cutters radially around the wire (again, just a bit). This cut the insulation without cutting any of the wires underneath. Until you get a feel for it, put the wire into a hole thats too big for it and work your way to smaller holes from there.

From there, I hand twisted the now-exposed wires so they bunch together and I’m ready for the next step.

Step 4

Crimp connectors onto the wires on the power cord. For this article I am using my new handy-dandy semi-auto crimping tool for the first time, rather than my manual commercial-grade crimper (i.e. giant pliers). The ‘semi-automatic’ part of this crimper is you just squeeze until the crimper releases, and you have a good crimp that is solid, and uniform with every other crimp you make for this job. Because of the small wire size, we can use the pink 18-22 gauge connectors.

Something to remember when you do this: While you are fumbling around the wire can slip partially or even fully out of the connector. Because of this I like to grab onto the connector with my crimper – without squishing it any just yet. Once I have it fixed in place, I use one hand to push and hold the wire end into the connector so it can’t slip back. Only then do I squeeze the bejesus out of it to make the final crimp and permanently connect the two wires.

Step 4 Complete. The semi-auto style crimper with its dual crimps was almost too big for this small 18-22 gauge connector.

Another something to remember: When doing one of these 3-wire connections, things can get awfully tight when you start finishing the connections in the next step. There may not be enough room to stuff the crimper’s jaws in between the wires to get the job done. Solve this problem by stripping enough of the plastic sheathing back from each side so you have enough open space to work with when things start getting crowded. If you can’t do that (I couldn’t here) then you’ll have extra effort in store trying to get the crimper’s jaws in the right spot while the wire stays in place inside the connector before the crimp.

Step 5

Now crimp on the wires on the other side – the charger side. This time, you have to pay close attention to which wire goes where. Since I live in the USA, our power cords do not adhere to the international standard for wiring colors. Connect:

The green wire on the cord to the green wire on the charger (GND)
The black wire on the cord to the brown wire on the charger (AC+)
The white wire on the cord to the blue wire on the charger (AC-)

Step 5 complete. Note the dual crimp lines on each side. The 18-22 ga crimper jaws were almost too large for this connector. You have to go right to the edge of the metal connector inside.

If you live pretty much anywhere else besides the USA, the wire colors will all match and what you connect to what will be obvious.

If you happen to screw up making one of these connections: Bite the bullet. There’s no uncrimping one of these. You have to snip off any crimped connectors at their very edge. Then snip down any wires you haven’t connected yet so they are all still the same length. Then re-strip and try again from scratch.

Step 6

Now you heat shrink the individual wire connectors. Remember the big heat shrink you put over the wire in Step 1? Make SURE you keep it well away from the heat gun while doing this. Let it get warm in the slightest and it’ll stick itself to wherever it is now, and not where you want it to eventually be.

I use my heat gun on its lowest setting, which is much slower going, but it lets me very carefully heat up my connector. I like to push the wires – and the connections – together a little, which spreads them out more or less evenly. Then I slowly rotate them around under the heat so every side of each connection gets heated up. You’ll be able to tell when you are done on each side because you will see a little bit of the internal adhesive squeeze out and form a bead on the wire. When you can see that – AND the air bubbles inside the connector disappear (this is another reason you slowly rotate while heating) you are done.

Heat up each END of the connector. Stay clear of heating the center over the metal connector. That center section is where you stressed the adhesive covering by smashing the hell out of it with your crimper. If that stressed area shrinks and tears, it will expose the metal underneath, and thats a bad thing. Let the center section shrink down thanks to the indirect heat coming to it from each of the two ends. Also, if you use a manual crimper, which is much more likely to cause a tear if you are a little overzealous, then staying away from the center will let the adhesive inside liquefy and seal up the hole you created rather than spreading it open via shrinkage.

Step 7

Let the wires cool a bit. Our next step is to slide the oversized, overly long piece of adhesive heat shrink over the connection we just made. If you try and slide it over while the connectors and wires are still hot… it’ll stick to them, shrink up a touch … and you’re screwed. So walk away for five minutes and be patient.

On this power cord, I am using an extra long piece as I want this to be a strong connection. I am also using an oversized tube that will just barely shrink down to hug the power cord, which means it will be very thick once it gets to its minimum diameter. I did this because this cord is going to take abuse as its going to be pulled, coiled and stepped on. Hopefully for years (it turns out when this stuff cools after shrinking its also completely rigid, which is a good thing for protecting my connection).

Step 7 complete. That little red ring of heatshrink near the plug is just a test I did to make sure the big size I used would shrink all the way down to hug the cord.

Application of heat is the same process as it is for working the connectors. Regardless of whether or not it looks like the heat shrink has shrunk down enough to do its job, take the extra time to apply heat to every angle of the exterior of the strip. Slowly go around all of it in even, top-to-bottom strokes. It may look like its fine halfway thru the process, but going around it and heating thoroughly at every angle will shrink it down tight on top of the other work you just did.

And… pay attention. Keep the nozzle moving and keep it on low heat. Its a whole lot easier to melt your cord than it is to unmelt it.

And thats the end of the AC cord input side.

The Power Output Side…

We did the power input cord in step-by-step detail. We won’t need to go into that same level of detail on the output side, since its almost the identical process. But there are a couple items worth calling out.

We need step-down connectors this time

The XT60 we are using for power output is a nice beefy 12 gauge, which would need a yellow connector. The Mean Well’s power wires are 14 gauge. Thats ordinarily a blue connector. So we need a step-down (yes, I could have used a 14 gauge XT60 – I do have them in my shop – but I prefer the heavier wire).

We do the same trimming to size the wire in the connector as before. However the 12 ga wires on the XT60 have enough fudge in the 10-ga-capable wire connectors that we can leave the tinned ends on. So no need to snip them, we just take some insulation off and job done. If you can leave the ends of a wire tinned, do it and make your life easier.

Bigger connectors = more room to work with

On the 18-22ga pink connectors, we almost didn’t have enough room to work with. But with the larger yellow 10-12ga connectors that wasn’t a problem.

You can see how the crimping jaws are within the borders of the metal segment on this larger connector; ending fully to the left of the slot in the middle. Lots of room.

The connectors, after applying heat to shrink them down onto the wiring, just before having the external sheath shrunk down over them. They essentially glue themselves and the wire connection together, providing a second of three layers of stabilization to the connection.

The finished product. I used red heatshrink over the wire on the output side simply so my stock of heatshrink (red and black) gets used up at about the same rate.

How To: Safe, Reliable Electrical Crimp Connections (part 1 of 2)

Solder or crimp? Debate on that can be fierce. After more than 8 years of daily commute riding, I have never had a crimped connection fail. How is that reliability accomplished?

We’re going to add this to the growing list of topics I never thought I’d be writing about. But it seems to need discussion quite a lot, and not just in ebike circles. I come across it frequently in the world of solar generators too, from folks who have zero experience with or initiation into the necessary skill of making extension cables. So while I am typically discussing DIY ebike topics, this subject crosses over into a whole lot of other areas.

Should I Solder or Crimp?

If you know how to do a good job of soldering, chances are pretty good you already know your answer. There’s nothing incontrovertibly bad about doing a proper soldering/wiring support job. At the same time, if you make good crimps that never fail, then there’s nothing wrong with crimping, either.

Can a case be made that either method is superior? Yes. I’m going to ignore the existence of this debate and instead focus on showing my tools and methods, which have resulted in a perfect reliability record so far. You decide for yourself if you want to go this route, or another.

What Tools Do We Need?

As is always the case, your success will be entirely predicated on using the right tools for the job. A crimping tool is not a pair of pliers for instance, regardless of the fact that you already own pliers and crimpers sure do look a whole lot like pliers.

Wire cutters

I use a dedicated set of wire cutters. Yes you absolutely can find yourself a single combined tool, or press tin snips or scissors into service if you already have those. I suggest you resist that temptation. Right tool for the job… remember? I use these, which I bought from Amazon.

You can find what amounts to the same cutters with a different label on them under about a zillion different brand names. These are actually cable cutters (not wire cutters) and they serve a good dual purpose in that they also work great for cutting bicycle brake and shifter cables (did I just violate the right-tool schtick I went on about just a second ago?). The best way to make a cut is to put the wire in their jaws and use a sharp, fast hand squeeze to snip the end off lickety-split. Trying to cut slowly and deliberately will give nothing but trouble with leftover wire strands. These bigger cutters will work especially well on the 10 gauge wire that is common on ebike controller input and battery output wires.

A good, strong pair of industrial scissors – with tiny serrated edges on the cutting surface to grip the wire – can work in a pinch. Regular household scissors… not so much.

Wire Strippers

Here again, you want a dedicated tool. I mostly use this one, again purchased from Amazon. I also have one made by Klein Tools that is marginally better… and double the price. While I like the Klein tool a little better, reality is I use the cheapie almost exclusively. So it must not be so bad, right?

Wire crimpers

Here’s where the magic happens. Its another tool you’d be tempted to not buy and just use a pair of pliers or something, but its very important to use actual crimpers. We’ll get more into why in Part 2 when we look at making crimps.

For the most part I use a 9 3/4″ manual crimper that I bought from Home Depot. I like it because I am used to it, but its probably better to use something like this Klein Tools semi-automatic crimper. It makes a uniform crimp that is perhaps more likely to leave the outer heatshrink surface of the connector completely intact – something you have to learn how to do after some experience with manual crimpers.

While the manual crimpers have been my tool of choice for years, I have the Klein tool on order right now and we’ll see how it goes when I use it in Part 2 when we get hands-on with crimping duties.

UPDATE:
One year after the above was written, I use the Klein crimpers exclusively. Both tools do the job but the semi-auto tool does it brainlessly and would certainly be easier for a beginner to master.

End Connectors (Pigtails)

So you have your wire on one side. You need a connector of some kind on the other. For an ebike, the common choice for a battery charge connection is an XT60 female connector with a 12-gauge wire. For the battery output its typically an XT90 female connector. A larger, more power-capable version of the widely-used XT60. Better yet, instead of using an XT90, make the connector an XT90S, where the ‘S’ signifies the anti-spark feature of that otherwise identical-to-XT90 version.

Tinned XT90S pigtails. The green paint signifies the connector is the anti-spark variant.

The cheapest way to create connector ends is to take a soldering iron and directly attach a connector to the destination wire. But an alternative shortcut is available to folks who may not be up for that, and its ideal for folks who are crimping connections. “Pigtails” – a connector professionally pre-soldered to a short length of wire – are commonly available, ready to crimp on with very little preparatory work. I use them almost exclusively.

My box of XT60 and XT90 pigtails, along with some pre-made extensions. Crimp two pigtails together you’ve made a cheap, short extension cord. You can see one in the center of the box (an XT60).

How much preparatory work is ‘very little’? Well on a pigtail, the bare wire ends are ‘tinned’. Essentially this means the bare wire has been dipped in solder, which makes it a single piece that cannot fray. You almost always have to snip off that end bit before you strip them. But we’ll get to that in Part 2.

Wire Connectors

All of the connectors I use are 3:1 heat-shrink adhesive ‘marine’ grade connectors. There are non-adhesive connectors (usually employing a 2:1 heat shrink ratio) which you should avoid. There are also connectors that do not employ any heat shrink at all. Same deal: Stay away from them and use only the adhesive marine grade version (unless you are an experienced hand at this, in which case there’s no reason for you to bother reading this article in the first place).

Why? Well, the heat will shrink tightly around the wire insulation on each side. This firm, adhesive grip will strengthen the connector’s bond, and support it. The adhesive liquifies under the heat and then dries, forming a strong gripping bond that ends up being stronger than the plain wire. Whats not to like about that?

You can find a variety of crimp-on ends. These two make up a detachable bullet connector that can be manually separated.

While there are a variety of connector types, including spades that let you screw a wire down, or bullets that let you uncouple and re-couple a connection manually, I almost always stick to butt-end connectors that just connect a length of wire to another wire. I do any form of quick-detach connections with proper connectors like an XT60 or XT90.

There are two sorts of butt-end connectors you should know about:

Straight-thru same-gauge connectors

These are pretty straightforward: You have the same thickness of wire on both sides. Or, more accurately, the thickness of one wire is within one size of the other.

Your yellow connector works for 10-12ga wire. the blue ones work with 14-16 gauge and the pink ones work with small 18-22 gauge (thats actually three sizes). But what happens when you have a bigger difference in the wires on one side or the other? You need a special kind of connector that has a smaller hole on one side.

Step-down connectors

This is the solution for connecting two wires of different sizes that exceed the ordinary tolerance of your standard straight-thru butt end connector.

The yellow connector is ordinarily used with a 12-10 gauge wire. But notice the blue band on the left? That side has a narrower opening that accepts a wire of 14-16 gauge. The right side, banded in yellow, takes the standard-for-that-connector 10-12 gauge.

The blue step-down connector has a blue stripe on the left for its normal 14-16 gauge wire. The red stripe on the right means its suited for an 18-22 gauge wire.

Here’s a connection using same-gauge connectors:

Above at left, I’ve connected a three-prong (grounded) power cord to a power input cord on an ebike battery charger I am making. The connectors have been crimped together, but have not yet been heat-shrunk. On the right is what the adhesive connectors look like after careful application of heat from a heat gun.

Notice how the adhesive covering of the connectors has not been broken or split despite being smooshed by the crimper. This is a big deal as if you split the adhesive shrinking surface, the split will widen when it heats up and make a hole with the bare metal of the connector exposed: an uninsulated path to a live connection (more on that in Part 2).

All this wire needs need now is some adhesive heat shrink covering the entire connection to finish off the job. And yes depending on where you live thats a funny looking plug. Its a ‘Schuko’ type plug and I was making a charger for someone living in the EU.

Heat Shrink

Once we completed the crimps as seen above, we need to cover it. This is to further stabilize/support the connection and protect it. For that I am using heat shrink tubing. Once again, there are two kinds of heat shrink: 3:1 marine grade adhesive heat shrink is the best. Stay away from the thinner, less sturdy 2:1 non-adhesive stuff unless perhaps you are putting on an external layer in a pretty color – over top of the 3:1 stuff – for the sake of cosmetic appearance. I have orange, green and white 2:1 heat shrink rolls for use on cable coverings for orange, green and white bikes I have built. But its just for show.

By using the thicker adhesive version you add another significant layer of protection over your connection. If it wasn’t going anywhere before (it pretty much was already unbreakable) its completely safe and protected now with a crimp, an adhesive grip on the crimp and another adhesive grip completely over top of that.

Left (above): the same plug already illustrated, with the wire now covered in adhesive heat shrink. Without looking right at it you might miss that its not a factory-made cord. See the red/black wires? That is the bare wire on the other end of that same charger (its not the same wire).
Middle: We take the two output leads on that black/red wire and graft on an XT60 plug to connect to our ebike battery. We use blue connectors this time because of the thicker 14 gauge wire.
Right: After shrinking the connectors, we slip a long length of 3:1 adhesive heat shrink over it all to strengthen and stabilize the new connection. Job done.

A Heat Gun

This is what does the shrinking. You might be able to use a hair dryer for this job instead of a proper heat gun. And it may work.

For whatever reason, I don’t own a hair dryer

One benefit of a heat gun is you can stand it up vertically on the garage floor, so you can use it hands-free. That gives you two hands to slowly rotate what you are heating up over it, to get a uniform effect without burning or melting stuff.

This is the heat gun I use. It has two heat settings and I almost always use it on ‘low’, which is slower but gives me lots of control over what is happening (its a lot easier to melt things than it is to un-melt them).

I keep the leftmost adapter permanently on the nozzle to concentrate the heat as much as possible. This minimizes the possibility of collateral damage to nearby wiring and connectors.

Quality Bulk Cable

One of the spiffs of having all this cable- and cord-making gear on hand is the ability to make just about any cord your heart desires. To do that conveniently, it will pay in the long run to buy the cable you are most likely to need in a spool. Say… 250 feet of the stuff. Thats going to seem expensive until you need a 50-foot extension for your solar panels and snip-snip-poof you have what you need in 30 minutes.

Sadly, the 250-foot spools don’t seem to be available at the time of this writing, but you can still get 100 feet of oxygen-free copper wire in 10AWG for under $1 per foot. You can spend more than this for bonded, PVC-coated wire that can take the outdoor weather and even be buried.

A quick morning’s work: A 50-foot extension out to my portable solar panels, sitting in the blazing summer sun. The short factory cable connects to a watt meter that I added to measure current, and that connects to the actual extension which leads outside to my solar panels. Created entirely from parts I already had in my garage workshop.

Next: Part 2 of 2. How To Do The Work, Step By Step

LED Strip Lights – Quick and Easy Part 2

You thought the last post on LED strip lights for a Larry vs. Harry Bullitt was a quickee? Lets be even quickee-er for this followup.

This post is a continuation of this one where I did the full description of how I added low-power-consumption LED strip lights to my Larry vs. Harry Bullitt… In less than an hour and with no wiring skills. No skills at all in fact.

I Moved The Switches & Batteries

I could stop right there with that heading and just show off a couple pics, but lets do a little better than that.

When we last left off with this little project, I had put together a neat set of working strip lights in a very short time. However, since I just slapped it together, there was one glaring omission: The on/off switches for the lights were inside the cargo bay, just sitting in a little unsecured bag.

Figure 1: Not going to win any design awards with this one.

Considering the Bullitt is a really stable ride, this was not such a big deal. But I shouldn’t need to go into the cargo bay to turn the lights on. Gotta fix that.

Background

That little bag was already there, holding the battery packs for my two front-wheel-mounted headlights. So it wasn’t much of a stretch to just toss in the USB power bank for the strip lights, and run the on/off switches over to it. While we are at it, we’re going to move and secure the power packs for those lights as well, and eliminate this little brown bag completely.

Figure 2: Low-mounted headlights on the fork, which created the need for the little brown bag

As you can see in Figure 1 above, I lined my cargo bay with a sort of 1-piece tub of super-dense closed cell foam. It is bolted down at the rear but nowhere else. Its easy to just pull the ‘tub’ up and run the wires underneath it, back to the cockpit.

Lets Keep It Simple

This is going to be real easy: I already have a handlebar bag. It holds my front motor controller. That bag is not right for this job, but it is also a MOLLE bag, so I can easily attach additional bags directly to it. I had a small, cheap bag in my leftover parts pile. It will hold the power packs for both the head and strip lights, along with the strip light power switches.

Figure 3: My handlebar bag. In this ‘before’ pic, the bag mated to it (at an angle) via MOLLE straps on the front is small; barely big enough to hold wallet, phone and keys.

Now we need a way to connect the wires up front to the batteries in the bag. Since they are nothing more than USB 2.0 plugs on both sides, I used simple USB 2.0 extension cables. The ideal length is 2 meters and these can be had from Amazon via their Amazon Basics USB 2.0 cable in a 2-meter length. Its possible to use USB 3.0 cables, but those are quite a bit more expensive versus the 2.0 cables that run about $5 each. I needed 4 of them.

Figure 4: Each connection to each extension is wrapped in silicone tape to waterproof it and ensure they stay connected.

I connected one to each of my four plugs at the front. Two to the headlights and two to the strip lights. Then run the cables along the floor back to the rear… bulkhead or whatever its called.

From there, run the wires up the bulkhead, out of the cargo bay and up into the handlebar bag. For the top portion, I zip-tied the 4 cables together for the sake of a neat appearance.

Figure 5: Peekaboo! looking back under the installed tonneau, which has been lifted up. You can see the bundled cable running up from behind the padded wall at the back of the cargo bay.

There is a fair bit of extra cable, which works to my benefit as it let me route the cables into the bag at precisely the point where the zipper opens it. I bundled the wires together with some non-permanent velcro ties; again for neatness’ sake.

Figure 6: The wires once they come up out of their bundled exit from the cargo bay. Much more noticeable thanks to the camera flash. Even in daytime they aren’t really visible against the black cordura background.

Inside the bag, the battery packs line the bottom, ends-facing-up, so I can plug directly into them.

Figure 7: The switches simply sit on top of the USB power banks. They are wired together to always face opposite one another with a simple wire tie – like you’d find on a bread loaf – for now.

The USB on/off switches from the strip lights are stuffed in here rather than getting creative and surface mounting them on the bag via the MOLLE webbing. My thinking is I want them kept out of the elements.

Figure 8: The complete picture, post-assembly. The little bag sits just above the tonneau and doesn’t contact anything. I keep those pliers handy in case I collect a nail or worse in a tire. I can grab them and pull out the jagged offender and let my tire sealant do its work.

End Result

Batteries and wiring are secure and out of sight.
Switches are easily accessible.
There is more than enough room in the bag, which is only half full at most.
Batteries are convenient to pull out when bike is left outside at a shop and I pull everything not nailed down and take it in with me. It is just as convenient to reconnect upon return.

One Last Thing!

My LED strips have an extension soldered onto each of them from the factory. They were originally 1.6M long and both, at the same point in their length, have a visible solder joint where they were extended. Since this is open, unsealed solder, thats an open connection. I’m not sure if a bad thing would happen if water ended up bridging the gap between those bits of solder, but lets not find out. I used a narrow bit of that same 3M mastic sealing tape I described in the original article to cover that connecting point and waterproof it.

That little strip of tape makes no difference in the appearance of the light when its turned on.

Thats it! Pretty simple, right? Carry on.