Sorry if this has been asked already but there are a ton of comments to wade through. Ten individual 18650 cells in series at a nominal voltage of 3.6 Volts would give me 36 volts. Assuming they are 2500 mAh a piece, then if I put 4 of these 10 cell in series packs together in parallel I would have a 10 Amp Hour battery correct? The same applies if I were to wire a pack together with 10 “4p” cells together in series. I’m trying to determine what the benefit of 10s4p over I guess what would be “4s10p”.
it would be applying huge amounts of force to the chain, which because of rust could become a weak point – if the chain were to snap, then the rider would be without any power whatsoever and might end up pushing his bike for 5 or10 km through soft sand while trying batteries for electric bike get home after a long day’s fishing – I suppose he could always carry a spare chain.
Well, I’ve finally built a pack, which in the end turned out to be a 16s6p/7p made from recycled dead laptop batteries, charging to 67.2V and has a secondary offtake for a controller on the 13s positive (i.e. to route 16s to the FETs and 13s to the control circuit). Some of the groups were OK for 12Ah from 6 cells, others needed 7 cells; I just used what I had and as I got the laptop batteries for free, it was better for me spend the time testing them than to use 80 new cells, which would have been quite expensive.
Really nice article you made here. very helpful. I do have some questions about the BMS board you used. Would you know where I could find any type of schematic for it because im trying to see whether I can use more then one of those BMS boards on one pack
The only thing left to do at this point is to add the connectors, unless you did that before you soldered the wires on, which I actually recommend doing. But of course I didn’t do that, so I added them at this step, being careful not to short them by connecting only one wire at a time.
Hi Micah,I am from INDIA want to construct a 36v,15 ah,peak current 15 amp,continuous current 6 to 8 amps. Now ipurchased 20 pcs new IFR 18650 lifepo4 rechargeable cells,and a BMS36v,lifepo4 BMS12s forE.Bike lithium battery pack 12s,36,v,PCm.How many cells total i have to use for my aim?What kind of charger (specification) i have to purchase? Your article and reply to questions are interesting.please guide me.
If you want to go 50mph and have a 500 or 1,000-watt monster motor on your electric bike you’ll need big expensive, heavy batteries, and you might as well buy a motor scooter or motorcycle. If you wan…
Hi Kim! Great question… I’ve heard some ebike companies and shops guestimate that 180 lbs is a good cutoff when jumping from 350 to 500 or 750 watts (750 is the highest allowable in the US). I’m sure you could get away with a 350 just fine, especially if you pedal along a little to help it get started each time and ride mostly on flats. Here’s a video interview I did with an individual of similar weight who was riding a 350 watt motor for over two years and using a throttle with higher powered 48 volt batteries… you can hear some grinding when the bike starts and I believe this is based on accelerated wear and tear. I hope this helps and welcome you to share what you choose and how it works down the line. I personally appreciate the compact size and efficiency (and lower price) of 350 watt motors but most people would recommend that you aim for 500+ watt in this case.
Next comes the heat shrink tube. Large diameter heat shrink tube is hard to find, and I got lucky with a big score of different sizes from a Chinese vendor before his supply dried up. Your best bet is to check sites like eBay for short lengths of heat shrink in the size you need.
Thanks for your reply. I am 190 lb. and 6 feet. I want to do mostly road work with some hills. I also want to do gravel trails made from old rail lines and so not really “off road” but not asphalt either. I love speed and acceleration and the ability to go far (even have a second battery on the rack to change out if needed? ). I am not a long time experienced bike guy and don’t like the totally bent over road bike ride. But can go from a somewhat lean forward and exercise ride to maybe putting on “after market” handle bars that allow for a more upright cruise ride as an option with my wife. Does this help? Also looking for an electric recumbent for my wife. c
Continue down the row of cells placing a weld on each cell. Then go back and do another set of welds on each cell. I like to do 2-3 welds (4-6 weld points) per cell. Any less and the weld isn’t as secure; any more and you’re just unnecessarily heating the cell. More and more welds won’t increase the current carrying ability of the nickel strip very much. The actual weld point isn’t the only place where current flows from the cell to the strip. A flat piece of nickel will be touching the whole surface of the cell cap, not just at the points of the weld. So 6 weld points is plenty to ensure good contact and connection.
Cool project! I’d check out electric rider (www.electricrider.com) as I know they have some good electric rickshaw and electric tricycle kits. You’re looking for a strong 48V motor that is geared really low. You want torque, not speed. With slow speed, something in the 1,000 – 1,500W is probably enough. Just don’t expect to be flying down the road…
Thanks for your kind words about my article, I’m glad it helped! To answer your question, I highly recommend avoiding a custom built charger. While it might be possible to use a DC-DC converter to change the output voltage of your 12V charger, the chances of a problem occurring are too high for my liking. The converter might not be smart enough to adjust the current down once full charge is reached. Technically your BMS should protect your battery from most overcharging scenarios, but if it is overloaded and a component fails, there is nothing to stop your cells from being destroyed.
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How do you determine this exactly? Your battery is a 36v 8.7Ah and I guess it has something to do with the maximum continuous discharge rate. It would help me (and maybe others) to explain why 30A is more than enough for this battery.
It’s a good question. You need to use a 5s BMS. You can’t use a BMS rated for more cells because if the BMS see’s that cells are “missing” it will likely trip the protection circuit and your battery won’t provide any current. I’m not sure how easy a 5s BMS will be to find. A quick Aliexpress search shows me that something like this will probably work.
Linear packing, on the other hand, will result in a narrower pack that ends up a bit longer than offset packing. Some people say offset packing is more efficient because you can fit more cells in a smaller area by taking advantage of the space between cells. However, offset packing creates wasted space on the ends of parallel group rows where gaps form between the edge of the pack and the ‘shorter’ rows. The larger the battery pack, the less wasted space is taken up compared to the overall pack size, but the difference is negligible for most packs. For my battery, I decided to go with offset packing to make the pack shorter and fit easier into a small triangle bag.
Hub motors come in two different types including geared (usually a planetary design) and direct drive or gearless (relying on larger magnets and no gears). Gears provide leverage, enabling smaller and lighter weight motors to achieve greater output but also produce friction, noise and wear. Most modern geared hub motors are built very well and should last for many years so don’t get too spooked. It may seem counter intuitive but geared hub motors do not add resistance when coasting. This is because they usually contain a freewheel mechanism that can unlatch from the axle and spin with little to no friction.
Alibaba.com offers 176,508 electric bike battery products. About 29% of these are electric bicycle, 22% are rechargeable batteries, and 8% are electric bicycle battery. A wide variety of electric bike battery options are available to you, such as 36v, 24v, and 48v. You can also choose from lithium battery, high voltage, and lead acid battery. As well as from 10 – 20ah, 21 – 30ah, and > 40ah. And whether electric bike battery is paid samples, or free samples. There are 176,462 electric bike battery suppliers, mainly located in Asia. The top supplying countries are China (Mainland), Taiwan, and Vietnam, which supply 99%, 1%, and 1% of electric bike battery respectively. Electric bike battery products are most popular in North America, Western Europe, and Northern Europe. You can ensure product safety by selecting from certified suppliers, including 39,033 with ISO9001, 14,496 with Other, and 6,372 with ISO/TS16949 certification.
You may have missed the point – I’m considering both front and rear motors together – 1,000W DD in the back (I figure there will be less wear and tear given the action in the looses sand) and a 350W geared motor in the front. They would be on separate throttles and the front motor would only be used very occasionally – if and when the back wheel really digs in. The rider’s pedaling is by way of assistance to the rear motor.My reluctance to deploy a BBS02 is based on:
Cyclone is one of the earliest producers of mid-drives, they are from hilly Taiwan. Although this looks like a simple drive set up, the Cyclone mid drive is actually a cylindrical Headway motor attached to a planetary gear-box, providing 10:1 reduction, attached to a double freewheel. Although the steel gears of the reduction are noisier than the GNG or BBS02, they are fully enclosed to protect them from dirt.
One of the most powerful, fastest accelerating, quietest, and beautifully designed electric bikes I have ever tested, premium drivetrain and custom battery. Surprisingly lightweight and well balanced front to rear considering the large 750 watt hub motor,……
Believe it or not, most BMS’s can handle the current from regenerative braking in the discharge mosfets as its rarely more than 5-7A. Some BMS’s (called two wire BMS’s) actually use the same mosfets for charging and discharging. Those inherently should be more than capable of dealing with the load from regen.
Actually I have ran into a problem – a few days ago I was riding it up a hill on a hot day when the power cut off and it wouldn’t start again. When I tried to charge it, the light on the charger just flickered from green to orange. I took out the battery and found that one of the cells had corroded from what looks like overheating. I think that the battery pack failure was most likely caused by too much of a load applied to the battery pack.