Combining the metals brings out the best in each. NMC is the battery of choice for power tools and powertrains for vehicles. The cathode combination of one-third nickel, one-third manganese and one-third cobalt offers a unique blend that also lowers raw material cost due to reduced cobalt content“
A very affordable 13S BMS that I like is this 30A version, though it can take a few weeks or even a month to arrive since it’s coming all the way from China. http://www.aliexpress.com/item/13-lithium-battery-protection-board-48v-lithium-battery-BMS-30A-continuous-60A-peak-discharge/1741121963.html
Hi Micah, I have been studying your how to build an bike battery, and enjoyed all the tips. I have been having a bit of difficulty figuring out the wiring portion of the construct however. For example, you talk of C, B and P pads and wires you solder to the top and bottom of the pack; the yet don’t put arrows to or refer to their colors for easy identification. The charge and discharge instructions for connecting are gone over rather fast with little for us to identify with exactly where to attach to, etc. Could you revisit your post here and include some baby steps for those who can’t follow the reference instructions you give for wiring the BMS?
But there’s still another issue: now if I just slip my pack inside some shrink wrap tube, I’ll still have exposed ends. This is more or less ok structurally, though it won’t be very water resistant and it will look a bit less professional.
The answer is that, unless you are seriously budget or weight constrained, this would probably be a bad battery investment. It might fit the bill initially for your commuting needs, but then it doesn’t really leave any reserve if you need to run some errands on the way home, or forget to charge it up one night etc. Even worse, as the battery ages over time the capacity drops. After a year your 8Ah battery is now only 7Ah, it’s only barely able to do your daily commute, and the next year when it is just 6Ah you now need to carry the charger with you and top it up at work every day.
When it comes to buying your cells, you might be able to find a local source, or you can order them straight from Asia. I prefer the second option, as you’ll usually get a much better price going straight to the source, even when paying for international shipping. One caveat though: do your best to ensure that your source sells genuine cells and not knock-offs. Do this by checking feedback and using a payment method that ensures you can get your money back if the product isn’t as described. For this reason, I like to buy my cells on Alibaba.com and AliExpress.com.
Finally found it. WOW!! Exactly what was needed. I struggle with conceptualizing verbal descriptions. You solved that! With the new JP Welder from Croatia my first welded build will soon be a reality. Thanks for all you do for eBiking!
I use white 2mm thick craft foam and cut out a shape slightly larger than my pack. I batteries for electric scooters replacement it up and seal it with electrical tape. It doesn’t have to be pretty, it just has to cover the pack. Your next step will hide the foam from view.
I just found your article, and as if it were destiny, this is exactly what I am trying to do (build a battery pack with BMS, and charge with charger). I am new to this, however, and have a question or two…
48 volt 1500 watt motor 48 volt 16.5 amp Samsun cell high quality battery 2amp charger, charges in 6 hours plus battery has USB port to charge your phone Top speed 35mph high torque Comes with every t…
Yea lead acid is a great way to cheaply get into ebikes and test new motor/controller combinations. Keep in mind though that your performance will increase when you switch to lithium. It’s easy to do though, as the bike doesn’t care what chemistry it receives, it just sees volts and amps. Good luck!
26\” wheels with Aluminum Alloy spokes. Opportunity: Outdoor Camping, Mountain. Speed up to 25km/h,High speed brushless shock. 36V 8AH Lithium-Ion Battery. Material: Aluminum Alloy. Mileage range: ≥40…
Your battery pack size is based on voltage and amp-hours. The higher the voltage and the higher the amp hours of your battery, the more range your battery will give you. A 48V 10-Ah pack gives you 480 watt hour (48 X 10). This gives you an easy way to determine exactly how much battery you are buying. The wattage of a battery is the only accurate determinant to judge what range your finished ebike will have.
The spacers you linked to make battery building a bit easier as you can set it up modularly, but as you indicated, they add a good amount of volume to the battery. I like to make my batteries as small as possible so I rarely use them. When I do, I use these ones, but it’s not very often.
As much as I want to build a pack just for fun and like buying tools like a spot welder I’m afraid of getting crappy cells at a high price. Whatj’s a good cell to charge at 1C for quick turn around and stay at a low price per cell? 36V 12A would be ok, more is a bonus.
If I regroup my 12 paralled cells in 10 modules, can I then join these in series using single wires (one for neg, one for pos) between modules, instead of wiring each terminals of each cells like you are doing. Could this affect BMS and/or have any negative impact on cells balance?
I like to cut most of my nickel strip in advance so I can just weld straight through without breaking my flow to stop and cut more nickel. I measured out the width of three cells and cut enough nickel strip to weld the top and bottoms of 10 sets of 3 cells, meaning 20 strips of nickel that were each 3 cells wide, plus a couple spares in case I messed anything up.
This is how most Asian batteries are built, since they use the same size aluminum or plastic case, but offer different sizes and capacities of batteries in the same case. I’ve used arts and craft foam, which often comes in sheets up to about 5mm thick (and I use a few layers to fill larger gaps). For MUCH larger gaps where that thin foam is less desirable, I’ve seen people use styrofoam or even that green molding foam often used in pots to hold up fake plants. That stuff is a fairly rigid though, so maybe a combination of that stuff and a layer of softer foam for cushioning would be good.
My thinking is that because each of the batteries is only 50% stressed, that the probability of problems due to overcurrent, etc. would be negated and I wouldn’t use a BMS for the supplementary battery.
It makes very little difference whether you have a small geared motor, a large direct drive motor, or a mid-drive motor. The mileage and range figures for a given battery have to do with how you use the ebike, not which motor system is on the bike.
When it comes to welding your parallel groups in series, you’ll have to plan out the welds based on your welder’s physical limits. The stubby arms on my welder can only reach about two rows of cells deep, meaning I will need to add a single parallel group at a time, weld it, then add another one. If you have handheld welding probes then you could theoretically weld up your whole pack at once.
What I would recommend doing is trying to ride again and when the battery cuts off, take it inside and measure the voltage of each parallel group before you try recharging it. Measure straight on the battery. If you find one group that is lower than the rest, it is likely the problem. It might have risen back up to a reasonable voltage with no load, but it can still be lower than the rest.
Maybe another way forward is to buy a pannier mounted supplementary battery pack (a proper one with a BMS) and to install it in parallel with the main one. The question then becomes whether to connect between the sprung terminals that go to the motor controller (which I believe to be the best thing to do) or into the little charging port jack. I presume that the charging port is connected to the charging side of the BMS and I don’t know how much current that port would take or whether it’s even a good plan to charge and discharge the main battery at the same time. I see significant potential for a high current through that small jack once I discharge via the main battery and a voltage difference exists between the supplementary batter and the main battery.
The lithium iron phosphate (LiFePO4) battery has had a lot of hype and media attention lately. This is the same chemistry used by A123 in the Dewalt power tool battery packs, where it has a 2000 charge and discharge cycle warrantee and has phenomenal current handling capability. The LiFePO4 batteries sold for ebike use generally have much lower current ratings, and the actual number of charge and discharge cycles that these generic packs will provide remains to be seen, although most manufacturers seem happy to claim 1500 to 2000 cycles. Iron Phosphate lithium packs are only slightly lighter than NiMH and a fair bit more expensive, but they could be the most economical in the long run.
Hi Sundaram, I’m not aware of many 18650 LiFePO4 cells, are you sure you are using that chemistry instead of standard lithium ion? Perhaps can you provide a little more detail about the specific cells you’re using?
A BMS isn’t necessarily strictly required – it is possible to use the pack as is, without a BMS. But that requires very careful monitoring of the cells of the battery to avoid damaging them or creating a dangerous scenario during charging or discharging. It also requires buying a more complicated and expensive charger that can balance all of the cells individually. It’s much better to go with a BMS unless you have specific reasons to want to monitor your cells by yourself.
With the voltage known, the next item to figure out is how many amp-hours will be required to achieve your desired trip distance without the battery running flat. This depends of course on how much pedaling you contribute to the effort, how fast you are traveling, and the terrain you are on. The following table is based on minimal pedaling effort.
When you wire in series you only increase voltage, not amp hours. So you’d have a 48V 5AH pack in that setup. Not enough range, in my opinion. If you want my advice, the single best upgrade you can do to that bike is to replace the battery and controller for 48V units. It will give you about 30% more speed and power. You won’t need to drill vent holes or anything, that motor can handle 48V as long as you aren’t riding up any 5 mile long uphills with a 250 lb rider. Shorter uphills and flat land will be fine all day long.