36v 10Ah Bottle Type Battery. Rated capacity: 10Ah. 36v 14Ah Rear Rack Type Battery. Rated capacity: 14Ah. 48V 14Ah Rear Rack Type Battery. Recommended to be used with 36V 250W electric bicycle motor.
Nissan, Imara, Microvast, and Zero E-motorcycles are now using NMC after extensive testing. Let’s take a quick run down memory lane to show how battery chemistry has evolved in just a few short decades. The following is not the order of their invention, just what my foggy memory recalls as seeing them used in E-bike battery packs.
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.
A quick note: when you get into large sizes of heat shrink, the method of quoting the size often changes from referring to the diameter of the tube to referring to the flat width (or half the circumference when in a circle). This is because at these large sizes, it’s not so much a tube anymore as two flat sheets fused together, sort of like an envelope. Keep that in mind and know what size is being quoted when you buy your large diameter heat shrink tube.
Unless you’ve got a specific design need, it feels to me like the two best value at the moment for a typical E-Bike build are 36v15Ahr and 48v10Ahr. With the choice being LiNiCoMn for smaller/lighter/cheaper or LiFePo for lifespan/higher-C but a bit more heavy/bulky/expensive.
my questions are obviously related to sla’s as this is what i have now but if answers differ according to battery chemistry i would like to know this as well for future reference any info much appreciated cheers craig
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.
Lithium batteries made specially for ebikes often come with specific bicycle mounting points making them easy to bolt to the bike frame, seat post or rear rack. If you go with a different type of lithium battery without ebike specific mounts, you’ll likely have to put it in a bag on the bike, which is still a good option, and one that I even prefer sometimes. (Link to blog post of mine about center frame triangle batteries).
I am however encountering problems in finding a BMS for my pack which will be 2 or 3 P and 7 S to replace 24V 6 AH in frame battery pack. Can you please enlighten me as to where I can access a suitable BMS. Thanks for any help. K.
I love this article and I am inspired by the knowledge here, I have a question, I need to build a 72v battery and the one I’m looking at is using 38160 cells, these cells are very expensive so how can I manage this the best using the smaller normal size cells like you’re using! Do I really have to make a battery 20 cells deep to reach this and to bump up the amp hours I would let say go 10 wide for a 30 amp hour right? Pretty close! Big battery but is it feasible or is there a better product
Absolutely, a relay is the way to go. Use the keyswitch you bought to activate the relay, then the relay will carry the heavy current flowing through your battery’s positive discharge wire. Alternatively, you could install 9 or 10 of these switches in parallel. Just make sure you mark your keys accordingly 😉
Next, regarding your question of paralleling the batteries. Yes, you can parallel them, and you can do it even before connecting to the controller. The biggest safety issue (and damage issue) though is to always be sure they are at the exact same voltage when you connect the two batteries in parallel. The easiest way to do this is only to connect them in parallel when you’re sure they are both fully charged.
Wear gloves. Work gloves, mechanic gloves, welding gloves, even latex gloves – just wear something. High enough voltage can conduct on the surface of your skin, especially if you have even slightly sweaty palms. I’ve felt the tingle enough times to always wear gloves now. In fact, my pair of choice for battery work are some old pink dish gloves. They are thin and provide great dexterity while protecting me from short circuits and sparks.
As long as you monitor your pack voltage so you don’t go too low during rides, then yes that would work. You’d simply run your discharge negative wire straight from the -1 terminal of your battery out to your controller, instead of from your -1 terminal to your BMS’s B- pad. But that removes the ability for the BMS to cut off the current when the voltage goes too low, so you’ve got to watch for that.
You would think they would help with cooling, but in reality there is little to no difference. They do create an air gap between cells but because that air is trapped inside the pack and can’t get out, it just turns into an oven. So you can glue your cells together and have them cook on a skillet or use those plastic spacers and have them bake in an oven 😉
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.
That might of sounded confusing, so let’s talk in real numbers. My pack is about 70 mm high and about 65 mm wide. That means that half of the perimeter of my pack is 70+ 65 = 135 mm. So I need some heat shrink tubing that has a flat width (or half circumference) of between 135 to 270 mm, or to be safer, more like between 150-250mm. And if possible, I want to be on the smaller end of that range so the heat shrink will be tighter and hold more firmly. Luckily, I have some 170mm heat shrink tube which will work great.
Is there same officially recognized method to come up with C ratings? Ping claims 2C on his LiFePo4 batteries, my Chinese-made “BMC” battery claims 3C. Can they just sort of say whatever they want? How do we determine the “real” C rating?
If none of our own battery offerings meet your needs, we can also highly recommend the knowledgeable folks at Batteryspace.com and EM3EV as alternate suppliers of lithium battery packs in a wide range of capacities, form factors, and voltages.
But what if you didn’t have to compromise? What if you could build your own ebike battery to your exact specifications? What if you could build a battery the perfect size for your bike, with all of the features you want, and do it for cheaper than retail? It’s easier than you think, and I’ll show you how below.
Thanks so much for this excellent information. I was wondering how to calculate the total amps for the entire battery? I’m trying to determine watts from this as I have a 24V 500 watt Rayos electric bike and am working to build a 24V 20 Ah battery (7s7p) battery and would like to know what watts it is capable of providing.
hello sir. nice guide FOR battery pack li-ion… i will try an electric bike kit for my 26″ MTB. and buy 1000w hub motor kit. i can solve my battery problem (expensive you know) with li ion pack. i have some questions,
THE SPOT WELDING IS ALREADY DONE! I KNOW ALL YOU “DO-IT-YOURSELF” E-BIKE AND POWERWALL BUILDERS OUT THERE ARE LOOKING FOR AFFORDABLE 18650 CELLS. I KNOW THESE AREN’T THE HIGHEST CAPACITY CELLS (1300MA…
I want to build some custom batteries, but I am hesitant to do the spot welding myself. Aren’t there modular and affordable pieces of hardware one can use to connect the batteries? Something like this?
I have found this BMS which is cheap (necessary for my project) and it is shipped from the UK. Because it is so cheap do you think that it may not be balancing? http://www.ebay.co.uk/itm/400984825723?euid=0502c7e2b2c744ec8857879d65d46e08&cp=1
The battery packs from Allcell are unique in that the cells are surrounded in a phase change material supported in a graphite matrix, which allows these batteries to handle higher sustained discharge currents without the cells overheating, and they have longer cycle life as a result of this thermal management. However, being ‘naked’ packs, they do not come in a rigid enclosure or bike mounting solution, The 48V 23Ah packs now come in a very nice rigid casing, though they still do not have ane explicit mounting mounting hardware and it’s up to the user to install them in protective case or bag on the bike. These batteries are available in http://twowheelev.com 17Ah, 36V 23Ah, 48V 17Ah, and 48V 23Ah options, and can handle 40A motor controllers just fine. They are assembled in the USA and have UN38.3 certification.
Regarding you question, if I understand you correctly, it seems that your 18650 lithium battery will be smaller than the old NiCad battery, so you have extra room in the battery box that needs to be filled, correct? My recommendation is to use some type of fairly rigid foam to fill the space. It adds almost no weight and it also helps cushion the battery pack.
Rated capacity: 10Ah. Recommended to be used with 36V 250W electric bicycle motor. Model: bottle type. Cycle life: About 1000 cycles. For this battery, it is better to be applied to motor in 350 W or …
I’m mostly familiar with BesTech’s 72V BMS’s and haven’t used a 52V BMS from them, so I can’t give you a recommendation on a specific 52V (14s) BMS from them, sorry. I have used this 14s BMS twice and it’s worked great for me on two 14s7p packs I made with Samsung 26F cells.
The sense wires generally connect to the positive of each cell group, but sometimes there is one more sense wire than parallel groups because the first sense wire is intended to connect to the negative of the first cell group, then all the subsequent sense wires connect to the positive of each cell group. Each BMS should be labeled on the board to show where each sense wire goes (B1-, B1+, B2+, B3+, etc…)
i am building a 10s4p 36v 18650 battery pack for my ebike, what gauge silicon wire you recommend for discharge and charge wires, i am using 2.5 amp 42.5v li-ion battery charger bought from ebay(http://www.ebay.com/itm/281639749374?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT), and 10s 36v 30amp bms bought from ebay(http://www.ebay.com/itm/182247900118?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) and 500w 36v controller.
Manufacturers usually rate their cells’ capacity at very low discharge rates, sometimes just 0.1c, where the cells perform at their maximum. So don’t be surprised if you’re only getting 95% or so of the advertised capacity of your cells during real world discharges. That’s to be expected. Also, your capacity is likely to go up a bit after the first few charge and discharge cycles as the cells get broken in and balance to one another.
your post have been extremely infomative, i am trying to DIY a pack for my electric scooter for a 36V and around 5AH pack should it be 10S 2P? sorry if i am not clear, kinda a beginner myself. and BMS wise what kind should i use?
The controller that came with my ebike conversion kit just has the label ’48v 1000w’ on it and there are no other specifications anywhere to be seen. I have emailed the suppliers asking if I could have a full list of specifications for the controller but am yet to hear back from them.