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.
If all I did was write internet posts, I’d still hate this idea. But circumstances made me try one. I knew almost immediately how wrong I had been.
Brace yourself, because, if you haven’t already tried it, and you are like most people, you probably think this is the worst idea, ever. I was one of those people. Then I built a bike that simply had to use a backpack battery as its power source. I held my nose, gritted my teeth and just did it. I dreaded the result right up until I rode it for the first time.
Look at the two pics below. Where’s the battery? Nowhere. Nowhere in the picture, at least. I was wearing it. In the image at right, I have used subtle visual cues to highlight the silicone-insulated XT90 connector I plug into.
By the way, that is a Cyc X1 Pro Gen 1 motor. The little bag houses a BAC800 controller that reached 60 amps of continuous output before I chickened out and lifted.
What problem are we solving?
A backpack battery should obviously not be your first choice, so why do one at all? When doing a DIY ebike build, there are some donors that just don’t have space for a battery.
Where the hell am I going to fit a battery on this bike? I will deliberately NOT answer that question here.
Fresh out of the box from Guerilla Gravity: My Smash 29er; one of their very last alloy frames before they switched to carbon fiber. The tires aren’t even dirty. Lets take a picture cuz it will never be this clean again.
In an earlier draft of this post, I wrote up all the different things I thought of or actually tried, and abandoned because they sucked for one reason or another.
But that is going off into the weeds as this discussion is about backpack batteries, not build or donor choices. So lets table all that talk and just stipulate: We have this bike that we have to work with. we looked at alternatives (remember… I hated this idea at the time), we are left with one choice:
The battery has to be in a backpack
Once I accepted the fact I was stuck doing a backpack, all that was left were materials and ergonomic/mechanical choices. i.e. just make it and do it right.
Pack Choice
If you listen to the experts on the internet (thats a joke in case you missed it), whenever the subject comes up you hear all about how a battery on the back of a rider is a bomb just waiting to go off. There is some truth to this. Flying off the bike and landing on your back on sharp rocks is a really bad thing made a whole lot worse if a li-ion battery is your crash bumper.
There’s also a lot of talk about how the world will end if you put your battery weight up on your back, but we’ll get to that one later.
The solution for safety is to use a hardshell pack of some sort, of the kind you see used on sport motorcycles. I picked a 20L Boblbee GTX from Point65.
Nope, it sure as hell isn’t cheap, but remember that unexploded bomb thing? Its for real and a hardshell pack solves that problem. It also provides you with spinal protection in case of a crash. And you also get something that addresses another negative the villagers are shouting about: A pack like this form fits your spine, hugs your body and never shifts – not even a little.
I suppose if you had to, you could use a soft pack and then stick your battery into a 30 cal or 50 cal ammo can. Drill a hole in a corner for the power cable exit and it would work, but that can is going to be a lot of weight to carry. Still, if you want a cheap, safe solution that uses a conventional pack… thats it. I’m sure you will figure something out on the shifting thing. I know I have packs that don’t shift. Much.
Really though… this is a problem you need to throw money at to properly solve. In my case I spent about half of retail by finding a vendor closing out an old model and blowing them out at a big discount.
Battery placement inside the pack
You do not want the battery bouncing around freely inside that hardshell pack. Each battery and backpack combo is different, but the core of the solution is to stabilize it with dense, closed-cell padding. I didn’t say wrap it tightly in foam so it overheats (put down that pitchfork). However, part of a smart DIY plan is to use cells that can take a murderous flogging without heating up in the first place. I used the old standby Samsung 25R cell for mine. For my pack, I have enough extra room to fit my pump and tire change tools.
Some judicious padding. Sprinkle some tool bags in there (so no little bags on the bike). Job done. Its not moving around.
The Smash, post build but before the first real ride (its too clean). All those bags violated my Anti-Festooning Rule and went into the backpack, although the top tube bag only contained soft towels meant for nutcracker protection. Maybe I should have left that one.
Figure out the wiring / connection
This is the tricky part because if you get this wrong and stay aware of the cable, you will hate your ride. First off, I used a short 8ga XT90S extension directly off the main battery output. I pretty much do this on every battery connection on any bike so, when connecting and disconnecting the pack, I’m visiting the wear and tear on a cheap replacement connector and not a live cable soldered into the pack. I also use a pair of XT60 pigtails to make a similar extension cable for the charge connector. Same idea. I’ve had my bacon saved doing this and the experience of just being able to throw away and replace a cheapie extension made this a go-to for me on everything.
The short XT90S extensions are at right. You think thats a lot of pigtails? Doesn’t take much to run out of spare parts… especially these days.
Next comes a long length of true 10ga power cord, made into a long XT90S extension cord. This is what will go from the battery to the motor and its several feet long. How long exactly? I measured out enough to exit the pack, run down my back, down thru my legs and still be long enough to never tug if I am standing on the pedals and bouncing around at the same time.
OK… great… what if I’m sitting down? A cable long enough to stand up with is going to be all kinds of awkward when doing what you do most: Sitting. I spent a fair amount of time trying to figure out what to do about this. A lot of others have done some sort of elastic bungie contraption. I tried that and felt it needed too much strain to extend, and carried a risk of pulling apart the connection at the motor. I needed something that reliably retracted my cable and extended it without much resistance.
And here’s the solution: The Key-Bak Super48 HD. This is literally the direct descendant of that chromed steel extendo keyring thing that every janitor in the United States has on his belt. Except they aren’t chromed steel anymore.
They’re kevlar.
The model I bought has a 48″ extension length, with their lightest 8 oz pull and a kevlar cable. Its so lightweight, it doesn’t impart the same feel of indestructability that the old steel pucks had, but I have been using it since mid-2019 and so far it shows no sign of wear. You can see from the Amazon link above that there are other models of varying lengths and pull weights. You can even get one with a steel cable. Since I’ve been using mine, I can say its 48″ extension is plenty, and the light 8 oz pull makes its operation completely unnoticeable.
How do you make the Key-Bak work?
What you need is a ball attached to your power cable. The cable threads through the key ring and stops at the point where the ball – which is bigger than the ring – is reached. You place the ball at a point down your back and to the side, so there’s more than enough cable slack to let you stand on the pedals, but not so much it gets in your way.
When you stand up the keyring lets the cable extend until the ball stops it. When you sit back down, it retracts back up behind you. Simple and effective. You never have excess cable down around your legs getting in the way. If you need more, the light 8 oz pull lets it happen without your even noticing its there. In fact, you really don’t know its there at all because its placed where you can’t see it, behind you and to the side. Out of sight and out of mind.
Once I spent some time figuring out the cable length needed to do the job right, and where the ball needed to be, I built and positioned the ball as follows:
A strip of leftover silicone handlebar grip roughly 1.5 inches long. Since I have used Wolf Tooth Fat Paw grips and ESI Extra Chunky XXL grips with my Jones bars on various bikes over the years, I have leftovers from grips that were cut off.
The silicone grip segment – since it was already sliced off a set of handlebars – already had a slit in it to let it slip over the cord. Wrapping silicone in silicone tape sticks instantly, and doing so – with overwrap onto the adjacent power cord, tightly affixes it so its not moving, ever.
Silicone tape fuses permanently to itself and isn’t going to unravel.
The above is just one way to do this. In my case with spare stuff laying around in my garage.
Here’s the whole setup, laid out so the cabling is visible (right side). Note the key ring and the little foam dingle-ball that makes the whole idea work. Click to zoom in.
A close-up of the keyring retainer in position. Note the inert (siliconed) XT90 cap over the otherwise open, disconnected battery-to-motor connection.
Whats With The Cargo Net?
With a 20ah battery, two small tool bags (one on each side of the pack) and an electric pump, the interior of the backpack is pretty much full. I found some hooks that work well with this pack on Amazon, and applied them to the pack and the net. Now I have the ability to stuff something onto the exterior of the pack. Usually that is my veteran Condor Summit Zero and maybe a small, flat pouch for wallet and phone if I can’t stuff them into the handlebar bag.
Funky hooks. Kind of a specialty choice that work just for this particular pack’s oddball equipment slots.
What is it like when you ride it?
I wasn’t expecting a good experience. The idea of being tethered to the bike and having a power cord running down off my back… I hated everything about that. Boy was I ever wrong, and if I hadn’t built the solution and gotten on the bike and tried it, I’d still be just as wrong. This is something you have to experience to fully understand and appreciate.
The Good.
You are still tethered to the bike. But the smart setup mitigates this so thoroughly its unnoticeable when you ride and requires very little extra effort to deal with.
Not having the battery weight on the bike makes it behave… like a bike. Internet experts will jump up and down and point to the higher center of gravity that comes from putting the pack on your back. But reality is that without the weight of the battery, smashing thru a rock garden or challenging singletrack is like doing it on an unpowered bike. Since in singletrack you usually only use (or want) power when going uphill, that means your ride everywhere else is exactly like you want it: Old school analog. Your suspension acts like it should… but with a rider who’s eaten too many cheeseburgers.
Having the battery on your back means you can shift its weight from side to side just as you already do with your body. See the above point, because that one and this one together completely undo the whole ‘center of gravity’ argument, and put the backpack setup in the ‘superior’ category when it comes to all-around performance. If you are wearing a 10 lb backpack… so what? You spent the money to buy a pack with a completely form-fitting back panel, that attaches firmly to you so its an extension of your body. No shifting of any kind whatsoever. You did that, right? Bought the really good pack? Cuz if you swiped your kid brother’s lunch pack or figured out some other way to cheap out… you’re screwed. Proper packs are not just ones that shield and pad the battery. They shouldn’t fidget.
Holy crap I totally forgot about that cable! I thought that was going to suck so hard, and I don’t even know its there! Thats you after your first ride. My first config ran the cable around my side and did not go thru my legs. I was concerned (and rightly so) the cable could flop away from my side and hang up on a bush. So I took the plunge and ran it between my legs like the experienced builders say I should. Sure enough it works perfectly.
We have addressed the safety/crash issue by using a hardshell pack, with some dense foam around it but not smothering it (and used a battery cell that doesn’t heat up under extreme load). That makes the battery safer than it ever would be in a ‘traditional’ battery bag.
Do NOT forget to carry along a safety plug to cap your pack’s power cord when it is disconnected. I am using an extra XT90 male plug where I siliconed over the power leads (and I added another bead once I saw the gap in this pic)
The Bad.
You are still tethered to the bike. I never said a backpack was the best solution. Its just the only one sometimes. Its not the end of the world if you do it right.
When you stop the bike, you have to disconnect. Its not difficult, but you have to do it so it goes on the list. I keep XT90 safety caps in a little pouch and use them to cover the open connections on the bike and my battery cable. When I mount the bike, I first lower the dropper post all the way. Then I straddle the bike from behind, standing over the rear wheel. I connect the power and, since the seat is so low, I can just step forward and be right over it. I then raise the dropper and I’m on the bike. Dismounting I have some options. I can be standing and reach down, disconnect and just throw my leg over like usual, or do the reverse of the mount from the rear. In practice I’m about 50-50 as the rearward exit is easier but I need to think about it to do it.
And The Ugly
Whats ugly is I used that unoriginal cliche for those pro and con section titles. Lets take a break, sit down with a plate of spaghetti and enjoy the movie!
Parking your ebike outdoors all alone? When shopping, my cargo bikes are locked but out on the street… but the battery goes in with me. Here’s how I do it without people thinking I am carrying a bomb.
Yes You Can Take ‘it’ With You
An ebike used for utility purposes is, by its nature, going to be left out a lot. You go to the store, load up a shopping cart, come back and fill up your saddlebags. You really want all the parts on the bike when you left to still be there. Especially after loading on 50 lbs of cat food, Oreos and diapers.
The most obvious way you keep the bike itself is to use a good locking strategy. I’ll save that for a different discussion. This time I will focus on how I protect the single most-expensive component on any ebike – the battery. Not by locking it up, but by making it so I can do a quick grab and carry it in with me.
By removing that battery, we are making that big heavy ebike into a boat anchor, which we can hope makes it at least a little less attractive to thieves.
Size (and Shape) Matters
What I am describing can be made to work with any shape battery, kept anywhere on your bike. What you see here works best with a squarish, oblong battery. In the pics below I am using a 17.5ah Luna Storm battery, which is pretty big and heavy (in part thanks to its powerful but not-so-energy-dense 25R cells). More likely, if you have a similar heat-shrink battery pack like this one, its quite a bit smaller and lighter.
I also keep a Luna Wolf Pack battery like this and do not use its magnetic mount. The battery is easy to quickly get off that mount, but leaving it inside of a bag like I describe here is, overall, easier than stuffing it in every time, taking it back out and so on. For packs like this (Wolf, Shark, Dolphin etc.) you could certainly bring a small pack and put it in/take it out as a part of your routine.
There’s more than one way to skin this cat, so what you see here is just a jumping off point.
Lets Get to It
This is the battery in its bag, just like it would be if I rolled up to the local Costco.
Ignore the charger cable in the front. I took this pic at work in my ebike garage.
If we zip open the bag, we don’t see a battery. We see an inner bag, along with that charger cable extending thru to the rear. The controller cable is in there too just out of sight (look closely and you can see it)
If we look inside the bag, we see the battery charge cable is in fact an extension running from the rear of the interior bag up and out the front. The motor cable – an XT90S connector – also has a short extension between the battery cable and the motor cable. The idea is this: when routinely, frequently detaching and reattaching the cable, if there is any wear its on a cheap, replaceable extension and not a critical, live/hot cable coming directly off the battery.
Disconnect the cables and give a tug to the inner bag. Here its shown halfway out but you will just pull the thing out in one motion.
When I leave, I generally put the cables back inside and zip it only halfway-ish, so its obvious there’s nothing worthwhile to steal inside. Move along.
Annnd here we are. the cables are shown sticking out of the inner bag. You will want to cap those for safety’s sake. I use cheap plugs I got a bagful of on Fleabay for a couple bucks.
And yes… as-is I have had someone ask me “what is that a bomb?” … only half joking and ready to clock me if I make a sudden move. So stuff the wires in the bag so they don’t stick out.
Tell the Bomb Squad to cut the red wire
Done! Wires are capped and stuffed into the bag in 5 seconds. The sling strap goes over your shoulder for easy carry. I just lug it to the nearest shopping cart and put it in the bottom rack with my helmet and off I go.
This is just a 3L hydration bladder pouch, the sling strap that comes with it and a shoulder pad I swiped off another strap I wasn’t using.
Parts
Its a really short list with one item on it.
Hydration Carrier
You see above the Blackhawk S.T.R.I.K.E. carrier in use. Purchase link is here. Yes, the name is a tad ridiculous. But this pack is minimalist and is just durable cloth with no insulation or padding. Its easier to stuff into a confined space. Mine came with a super sturdy velcro sling strap.
Another that is well made (and a tad smaller for a tighter fit is sold by Voodoo Tactical. It comes with thin backpack-style shoulder straps that don’t take up *too* much space in your triangle bag and are not enormously fiddly when stuffing back in there.
Another one I use (with my Luna Wolf pack) is this government-issue USMC carrier. The link is to a brand new unit. I got mine surplus and cheaper on Fleabay. This pouch has no straps (you can clip on your own from a duffel bag if you like) and it is the opposite of the Blackhawk carrier: Its thick and padded. I can still stuff it into any triangle bag I have despite this. Its great as a protective layer over a battery.
Wrapping It Up
There are lots of ways to do this. How I do it is no big deal. Key takeaway here is to find a method that works for you so you can swiftly grab the battery, go off to your next adventure and then come back and plug right back in again.
Whats an 80% charge on a 48v battery? on a 36v? 52v? These charts give answers to questions like these on all common ebike battery voltages.
Remember, ALL numeric charts show ballpark values that may be numerically correct, but no generic chart can match your individual cell characteristics, your pack’s age or its chemistry. Bottom line: imperfect charts like this are still good baseline references. Use these and teach yourself how to read the voltage gauge on your display screen.
Quite some time ago, I produced a series of charge status charts for a variety of common lithium-ion battery voltages. They’ve become a fairly common link to help folks out on various Facebook groups who use these battery voltages in their ebikes.
I built them using Google Sheets, so they are not web pages, which I suppose has kept them from being widely linked in search engine results when people are looking at such things.
Here for the first time are direct links to the charts on a normal web page.
36 Volt (10S) Battery Charge Chart
The first link is to the lowest voltage: 36v. Generally this is the lowest voltage you will find on a modern, commercial ebike. Note that its called ’36 volt’ but really that is the ‘nominal’ value. A 36v battery is actually fully charged when it is at 42.0 volts.
Click on the image above to be taken to the actual 36-volt battery charge chart.
48 Volt (13S) Battery Charge Chart
The next common size is 48v. These batteries are fully charged at 54.6 volts.
Click on the image above to be taken to the actual 48-volt battery charge chart.
52 Volt (14S) Battery Charge Chart
The next battery voltage is 52v and very common. 52v batteries will work on systems designed for 48v, and why is easier to understand when you become aware that a ’48v’ battery really tops out at over 54 volts. A ’52v’ battery tops out at 58.8v, so it essentially lets you use a 48v system for a longer time at higher voltage levels that it is already designed to utilize.
Take a guess what you are supposed to do to see the 52-volt battery charge chart.
60 Volt (16S) Battery Charge Chart
With a 100% charge voltage of 67.2 volts, when you have one of these you are getting into high voltage territory
How about a charger – quickly adjustable for voltage and current – that is rated for hundreds of thousands of hours of use before it typically fails?
… Some Assembly Required
Please take note: Mean Well LED power supplies have been used by the DIY ebike community for years. The concept is not new. The weak link here is you and if you screw this up consequences could be profound If you know your way around a crimper, or a soldering iron… great this will be easy. Kid stuff. If not, don’t pick this project as your first learning experience. With that said, here is a complete instruction set on making one of these units.
Why reinvent the wheel here? What benefit could be gained?
Ebike battery chargers tend to be dodgy. The interwebs are filled with stories of frequent flyers whose chargers keep dying. Its either a dead fan that in turn lets the charger heat up and fry, letting the smoke out of the internals (never a good sign) or perhaps the most common: the charger stops cutting off at its cutoff voltage and keeps on charging … with potentially catastrophic results.
So… what is better? You can see that in a popular commercial battery charger: The Grin Satiator. Its so efficient it needs no fan to cool it (or to fail). It is also largely weatherproof and highly reliable. The only demerits it gets from users – which have largely gone away over time – are programming/firmware issues.
Oh and its cost is US$300+ once you figure in a programming cable, along with a couple of adapters. I bought one. It works perfectly. But with an AWD bike with 2 batteries that I ride every single day and charge both at home and at work, I found convenient charging means walking up and plugging in. Not carrying chargers with me, unloading them, setting them up etc. So 2 batteries x 2 locations = four chargers. $300×4= not happening. And I carry a charger with me in case I get stranded. $300×5=crazy talk.
What to do? Use the same core hardware that gives us the $300 charger but without the fancy user interface. That could cost as little as around $40 if we are lucky, and $90 if we are not (or we buy a more expensive option). We won’t have a fancy display screen or onboard memory, but it will still be adjustable with a screwdriver.
The dollar is for scale – and to remind me what money looks like since I can’t seem to stop handing it away.
I have worked with three different models that can serve my purposes. Remember that volts x amps = watts and this will be important when figuring out what to set your charger for:
CLG-150-48A
Discontinued. See next entry below for replacement
Available regularly on Amazon for about US$55
Rated to 150 watts
Rated as adjustable from 40 to 56v but actually adjusts from 39v to 58.1v
Usable as an 83% to 100% charger for a 36v battery
80% to 100% for 48v battery
80% to 96% for a 52v battery
Minimum amperage selectable is about 1a
Lower wattage rating means it must be set to lower amperage on 52v batteries (2.5a max for a 52v battery)
Constant Current + Constant Voltage (CC+CV) output (i.e. ‘smart charging’: Ramps power down slowly and precisely as it approaches target voltage.
Designed for LED lighting and ‘moving sign’ lighting applications
IP65 rated for indoor and outdoor use.
Usable at EU or USA voltages.
Mean Time Between Failure (MTBF): 303,700 hours. Yes, really.
Street Price around $90. Often available on EBay for around $50, even down to as little as $25 each if someone is selling off a pair of them wired together as Zero e-motorcycle chargers.
Essentially same specs as the HLG-185H-54A but is instead rated for 320 watts
Current can only dial down to about 2.0 amps. But the high wattage rating means it can be dialed UP to make it a 5 amp charger (only aftermarket battery plugs like XT60 or Andersons are able to safely handle this current level). 5 amps x 58.8 volts = 294 watts.
MTBF: 157,100 hours (just under 18 years of continuous use)
The 320H units I have bought on the aftermarket were originally wired together in pairs in series and used as onboard 115v Zero Motorcycle chargers
SIDEBAR IP65 Enclosure – IP rated as “dust tight” and protected against water projected from a nozzle. So these chargers are safe with:
Garden hose spray (or heavy rain) – Yes
Ocean waves – Maybe
Bottom of fish tank – Hell no
Myself, my bikes have 52v batteries. I do use a couple of CLGs at work for my charging station there but only because I hadn’t found the HLG-185’s yet. The HLG-185’s are ideal chargers as they can charge at levels safe for the Sondors battery plugs (3a max) and can handle any voltage asked of them for a 48v or 52v system. If you have an aftermarket battery that does not use the pin plug as do the Sondors batteries, then you almost certainly have an Anderson Powerpole, an XT60 or an XLR connector. Those plugs can handle the higher amperage the 320 is capable of delivering. I use a 320 as a travel-with charger under the theory that if I am stuck somewhere I want to grab as much charge as I can, as fast as I can. But a 185 is perfectly capable of being a 3a charger and weighs probably half what the 320 does.
This pic was supposed to show everything needed to make the charger, but I sort of overdid it. No need for a whole bag of connectors, or heat shrink, and that grey cutter isn’t needed either.
So… enough details already. Lets make a charger!
Here’s what we need:
A Mean Well power supply. The process is identical for all models.
A pigtail’d grounded electrical plug. They are sold on Amazon typically as replacements for corded drills and similar power tools. NOTE: I am using a USA standard plug, but these units are made to accept worldwide voltage/current so just go to your local hardware store and choose your local version of a pigtail’d, grounded power cord if you live outside the USA. Oh, and read the spec sheet to confirm what I just said applies in your country.
A digital watt meter to tell us what we are outputting to the bike. For almost all of my chargers I use $15 inline watt meters. This is optional but very desirable.
An interface from the charger to the battery. I will use an XT60 as the direct connection, which is what a lot of aftermarket batteries use. You can then plug just about any adapter into that for your Sondors or whatever else you have. Note in the picture above, bottom center just to the left of the little adjustment screwdriver we will keep with the charger, that there is a pin plug adapter for use with Sondors batteries. That one came from Luna Cycles.
A Note on Battery/Watt Meters
Here’s the short version: They suck. Or more accurately they are oftentimes off by a bit, and there is no way to calibrate them. Its not uncommon to see a battery meter accurate to within 2%. That sounds ok unless you are charging to 58.8v, which could be 59.98v with a 2% error and that is very, very bad. So you want to take a multimeter or similar *known safe benchmark* (in a pinch the reading on your LCD screen will work once you have disconnected any charger from it) and use it to learn where your chosen meter is in terms of its accuracy. I do this and then I take a labelmaker and make a label telling me how much a meter is + or – actual voltage.
So for example, if my target voltage for a 52v battery is an 80% charge of 55.4v, and my watt meter is reading 0.50v higher than it should be, then I create a label that says
+0.50v
UPDATE: This link is to one of many cheap Chinese watt meters. The last two I have used, purchased across a span of 4 months, exhibited a new and consistent behavior: Plug them in and they are WAY high, by like 1.2v. But sit and watch the meter over a span of about 5-10 minutes and you will see it slowly auto-correct itself down to a steady reading. This steady reading will still be off by a bit but not so bad… these last two meters were both off by only about 0.20v… so I recommend these as your best option – and recognize they have a calibration stage at startup that you need to wait out.
So now, we have our parts in hand and its time to assemble them. In order the steps are
Step 1
Attach the pigtail’d cord to the input side of the Mean Well unit. For the USA plug and the Hanvex drill cord I have been using, the wire sequence is green (cord wire) to green (charger wire) for ground, black (cord) to brown (charger) for AC+ and white (cord) to blue (charger) for AC-. Note that the wire colors are noted on the charger left side, but as ACL and ACN. DO NOT SCREW THIS UP. These are international standard designations and colors which as usual the U.S. does not follow. If you want to check my work, start googling. Myself, I use marine heat shrink butt end connectors to connect the wires. I also use rather expensive electrician’s-grade crimping pliers. There is a big difference between proper crimping pliers and … well, pliers. Use the right tools for the job. After I crimp, I heat shrink the connectors, add heat shrink around each individual wire and then do a heat shrink around that entire assembly. How you do it is up to you (i.e. soldering or whatever). Remember that this is mains power you are fooling with here so get this right.
Step 2
Attach a battery side plug. In this case I am using a male XT60 which both works for my aftermarket batteries that have female XT60 charge plugs, and my bottle batteries where I use my XT60-to-pin-plug adapter. Same procedure as in Step 1 although a little simpler as there are only two wires. Note that some of these charger units do not use red and black wires. If you are not familiar with what the colors mean, the casing on the unit specifically tells you which wire is which (V+ and V-).
When you are done, you will have something looking like this:
A completed 320w charger without the watt meter stuck on the end
Step 3
OPTIONAL – attach an inline watt meter to the output side of the Mean Well unit. This is your power display. I call this step optional because you could just calibrate your charger output once and not use a meter to monitor progress (easy enough to turn on the bike display during charging, which will hurt nothing). Myself personally, even though meters are pesky insofar as getting them calibrated, I prefer to have a real time progress monitor I need only glance at. NOTE: Source side of the meter gets connected to the charger. Load side goes to the battery.
Step 4
OPTIONAL – make an extended output cord. Essentially one big extension cord on the battery side. You’ll know real fast if you’d like to have one of those as whatever you made doesn’t reach. You could just hardwire this to your output lead on the charger. But then you are stuck with that length alone. I prefer to make a cable as I have no problem using a couple of 12 AWG XT60 pigtail ends to make a dedicated extension.
Step 5
Connect an interface to your battery. For a Sondors, this is a pin plug connector. For many batteries the generic standard is a male XT60 connector. You can either buy a direct-connect bottle battery adapter (see link) or connect a male XT60 pigtail and then buy an XT60 Female-to-bottle adapter. Doing it the latter way makes your charger able to connect to any battery (if you have another battery with say XLR connectors you can make an XT60-to-XLR adapter via a couple of pigtails). You just swap in the adapter you need. In this case I am picturing a Luna-sourced XT60 female to pin plug adapter. A different source for the same thing is in the parts list below
Step 6
Go out and buy a little Phillips head screwdriver. This tool will live with your charger forever so you should buy a new one unless you have an extra already. Its a must-have for the next step. Also required if you plan on changing your settings (lets say you want to charge 80% one day and 100% the next).
If you have performed all of the above steps, you now have a parts pile that looks like this (well sort of, the meter and the charger have already been labelled with calibrations but just pretend we haven’t done that yet):
Charger, adjusting screwdriver, extension cable and watt meter complete with sticky note showing how far off it is.
Step 7
Dial in your output voltage. Once you have connected an AC plug, and a battery side connector AND connected the inline watt meter, you simply have to plug the new charger into the wall. Amps will read zero and volts will read whatever the unit is currently set for. See the little rubber whatsits that are capping the voltage (Vo ADJ) and amperage (Lo ADJ) adjustors? Pull those off and stick the screwdriver into the Vo ADJ hole. Twiddle it around gently until you feel it seat into the adjustor. Now turn it first one way, then the other. Watch the voltage readout on your meter. One way goes up, the other down … and the directions are different on my 185’s and 150’s vs. my 320 so you figure out what direction does what yourself with your own unit.
Step 8
Calibrate your meter to reality. Remember what I said above about meters. You need to figure out how far off your meter is from your display. As you can see if you look closely above, this meter is off by +0.50v. Thats a fair bit. The good news is when these types of meters are off, they are consistently off so you just need to know by how much (and if you can find a meter that is consistently accurate tell me. I can’t find one at any price). this is a pain but you only have to do it once.
Step 9
Dial in your output amperage. OK… moment of truth time. You are plugged into the wall. Time to plug into your battery. Maybe you should do this out in a field with a long extension cord. Don’t do it in the baby’s nursery or in Grandma’s bedroom while she’s asleep. Plug the battery in and now watch the meter. The voltage switches to now show the battery state of charge. The amperage comes to life and shows the current level (amps) being fed into the battery.
Once again, like you did with the voltage adjustment, use your screwdriver this time in the Lo ADJ socket and twiddle it until you see the safe amperage rate you safely want to safely run your charger safely at. Did I forget to mention safety? And volts x amps = watts ? Pay attention and get this right. If your meter is off – especially if it is reading lower than actual voltage – you will want to find out by what percentage it is off and adjust your indicated meter amperage less that percentage amount.
IMPORTANT SAFETY TIP:
Your charger does not switch its power feed on and then off like a light switch. Instead, it will slowly ramp down its current delivery level (amperage) as the battery approaches your target voltage. So that means if you plug in a battery that is fully charged or nearly fully charge, you will get a really tiny reading of current going into the battery – and this will give you a false idea of the amperage your charger is set for. Because of this, when performing calibrations you must have a battery that is at least a couple of volts low. At least. If you are charging to 54v (100% charge on a 48v battery) then plug in a battery at no higher than, say, 50v state of charge.
If you are using a pin plug, NO MATTER WHAT make sure this value does not exceed 3 amps. The plug can’t safely take more. Again, remember that volts x amps = watts. So if your 185w HLG-185 is feeding the max of 3.45 amps, that means at 58.8v it will be sending 203 watts which exceeds its 185w rating and thats VERY bad. Here again. Use your brain and don’t screw up. Best to leave a safety margin. For example I have one of these set to a ‘full’ charge of 58.3v and 3.0 amps. 175 watts.
Step 10
Add a carrying case? Your basic MOLLE water bottle bag will fit this all beautifully. the slightly larger Condor bags available on Amazon will do so with a little more fudge room. I got two green ones on sale for $5 and $8 respectively. Sometimes they are more. Happy hunting. In the end what do you have? A charger that you can expect to be reliable literally for years. Not necessarily cheaper, but dependable. If you buy this once you won’t have to buy it again in 6 months or a year… and thats the usual story out there in ebikeland for the more demanding users in the DIY world.
Parts (remember oftentimes you can get these chargers for a lot less on clearance on Fleabay). Especially the HLG-185 which is commonly used in street lights):
XT60 male and female pigtails (need 5 total if you are using an inline watt meter, extension cable and xt60 lead for battery) https://amzn.to/2OTj6bg (8.99)
Everything nice and neat in its own traveling packageThats a size 10 1/2 shoe there for scale.
UPDATE:
I had the opportunity to make another charger over the weekend for my daughter and son-in-law. They also live in the EU and as such I needed the appropriate plug – the charger will auto-sense the voltage coming in and adjust accordingly. So for those of you folks outside the U.S., here’s what one looks like.
My daughter’s locale uses a 2-prong grounded ‘Schuko’ type plug. One nice thing about using international parts is they conform to the same international specs. So there is none of the translation necessary to pick which wire goes to where. Just match the colors and you are done.
Proof I am not colorblind (ps that dress was white and gold)
This time I took the time to take pics before and after during assembly. The heat shrink and adhesive on the marine-grade splice connectors make for a very solid connection. There is a trick to doing the best crimping:
do it on the very ends
don’t crimp so hard you tear deeply into the plastic covering the splice
ensure the pointy prong on your crimper faces AWAY from the other wires so if you do overcrimp and tear into the plastic, you won’t expose metal facing the other wires.
Use a halfway decent crimper. I think I made this point in the original post but it bears repeating. Use the wrong tool for the job and your results will suck.
There is also a trick to heating the adhesive connectors – First, use a nozzle on your heat gun that narrows the heat exhaust so you can better direct it to a small area. Next, heat the ends that you actually need to shrink up and grip the wire. Stay away from directly heating the metal center. If you do that, any tearing of the plastic over the crimp tends to actually seal itself. If you heat the center, those tears will break open further as the adhesive plastic shrinks from the heat. Its actually pretty easy to do… you just have know to do it… and now you do.
If you live in the USA, no I did not use the wrong plug.
Heat shrink over top of those adhesive connectors and you have a stable, solid connection you need to look for to notice.
Do it again for the XT60 ‘universal’ output connector. Make sure that external heatshrink is plenty long. In this case I made sure I had plenty of exposed wire on the end because I like the flexibility. If I wanted to reinforce it and maintain that flexibility, self-adhesive silicone tape (sticks only to itself; spiral wrap it around the wire) is the perfect solution. The Sondors-compatible bottle connector I chose for this charger had a male plug end on it, so I needed to make another connection using a short female-to-female XT60 extension. It is important to get your genders right on a charger. You do NOT want a male XT60 or male anything else exposed on the battery side as an arc between the terminals is much more likely on a male plug, and that can destroy your battery.
Here’s the whole thing put together with a meter added to the end and the Sondors-compatible 5.5mmx2.1mm barrel connector attached. The meter is showing it is configured for an 80% charge on a 52v battery. After I took this pic I realized I needed to set it up for a 48v battery and changed the voltage on the charger and the label on the meter.
Lastly:
These chargers are sturdy enough and water-resistant enough to mount on your bike as an onboard charger. Here is one bolted onto a front rack. The cords are gathered up in a MOLLE dump pouch attached to the handlebar bag. Just open the flap and pull out the cords.
