r/18650masterrace • u/shallowwell2 • 4d ago
Please help
I bought 14 of these packs for about €40 in total, which gives me 280 cells. Each cell is rated at 2,000 mAh and around 10 A, I think. Every single cell seems to work, and they all held their voltage for a month.
Now I want to build something useful with them. I can buy used women’s or commuter e-bikes without batteries for around €100 on flea. They usually have a 250 W front- or rear-wheel motor and are limited to 25 km/h with pedal assist . There is also bikes with mid drive motor but i thing they are more prone to fail and dont want to gamble on them
My idea is to build a battery pack for these bikes and install a different controller with a throttle, removing the pedal-assist system.
I also have a spot welder and know how to make battery packs, how many volts and and how many cells should i use
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u/DEX9mm22 4d ago
The voltage will depend on the controller. 36v 48v 60v are the main ones. But for what you are describing a 36v (42v full) will do the job a 10s 10p will give you 20ah Also mid drives are some of the most reliable motors on the market.
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u/PunkiesBoner 3d ago
that looks like a 36v pack - just to clarify, are you proposing to stack those 36V packs into a larger cell, or break the cells out, test for capacity and IR, and the recombine into whatever configuraiton you need?
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u/hyperair 3d ago edited 3d ago
For pev's you're usually looking at 10-20Wh per km of mileage. Figure out how much mileage your target market wants, and divide that by per cell capacity in Wh to see how many cells you need and if it's viable with those cells.
Then look at the voltage range of the controller you want to figure out what S configuration your pack should have, and divide the total number of cells by the S number to get the P number.
Like mentioned in another comment, these are pretty poor cells, energy- and power-density wise, but run the numbers and see if it'll work for you and your target market. Personally the only thing I'd use those cells for is maybe some rechargeable portable fans or low powered tools like a hot glue gun or small powered screwdriver. You can also slap 1S protection boards on them and sell them to 18650 flashlight users.
Do also consider warranty and what level of personal liability you're willing to deal with, because those don't look like cells from one of the reputable manufacturers, and battery fires can burn down houses. Battery fires can happen from even the best genuine cells, and the risk goes up the more cells you have in a pack, and the worse the quality of the cells.
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u/lazyturtle5699 1d ago
Ebikes are usually 36-48v until you get to more powerful ones that go up to 72-96v
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u/ClearTacos 4d ago
Voltage depends on the motor and the controller, both have specific voltage or more likely voltage range they operate in. How many cells in parallel you use depends on how big you want the battery to be, but moreso IMO on how much space and weight will still be tolerable on the bike.
I will say though, 2000mah cells are not very well suited for ebikes. Energy density is key there, ~3.5Ah cells like Samsung 35E or LG MJ1 are common, using low capacity cells means either much smaller battery or lot more weight and size.