Hi folks - I can’t vouch for the company but if you’re willing to gamble a little you can get single 3.2v nominal 20 ah Yesa LiFePO4 cells for 9.99USD ea. The site is Refurbished Electric Bike motors, Store Demos, Yard Sale, Bargains, One-of-a-kind They are in Texas, so US shipping should be quick and reasonable. They say these were ordered by a scooter manufacturer but were not up to the task so they have “thousands” to sell. I don’t know but I think these might be the cells: LiFePO4 Battery,LiFePO4, the best choice to replace Lead acid battery! If so, they are 2C continuous 4C burst, so they’re good for 40 amps continuous. Burst usually means no more than 5 seconds every 30 seconds. Both terminals are on top and look like they are threaded, so it would be easy to hook them up in series. Just stand them upright in a box and connect + to – with drilled bars or wires and terminals. 4 in series is 12.8 nominal so these are essentially $40 for a 12 volt 20 ah lithium battery, if all the cells are good. They clearly state there are no guarantees. LiFePO4 are 14.6V right off the charger but are usually in the 13 to 13.6 range during use. By my calculations a 12V battery (4 cells) would be under 6x3x6 inches and weigh 6.25 lbs.
LiFePO4 are the “safe” lithium cells that are very stable and unlikely to catch fire or explode if charged or discharged too quickly (like by short-circuit). These special deal cells are sold without a BMS (battery management system). The BMS keeps all cells in balance and prevents overcharge or overdischarge, which can be a problem with lithium batteries. There are separate BMS systems available but some people (including me) believe that you can watch your cell voltages and balance the cells manually, especially if you don’t draw too heavily or discharge too deeply. I am running similar 20 ah LiFePO4s that I got from ElitePowerSolutions.com. I am still collecting data but as an example my 24V 350W shift kit mtb used about 9ah on a hilly 13 mile ride with moderate pedal assist. The maximum amps was under 28, so I was well under the limit for 20ah 2C batteries. I find the individual cells are usually within 0.1 volt of each other off the charger and nearly dead even after some use. For instance after that 13 mile ride each cell was 3.27V. The total was 26.17V so the 24V motor still had plenty of pep. By extrapolation, I should be able to go 25 miles on a charge. Not bad for a 13 lb battery - jd
ps - in re-reading the specs on the site, these are 1C continuous/2C burst, so they're not the Yesa's I found. Still might be worth a try. Also, look into a LiFePO4 charger for best charge/longest battery life with lithium batteries
LiFePO4 are the “safe” lithium cells that are very stable and unlikely to catch fire or explode if charged or discharged too quickly (like by short-circuit). These special deal cells are sold without a BMS (battery management system). The BMS keeps all cells in balance and prevents overcharge or overdischarge, which can be a problem with lithium batteries. There are separate BMS systems available but some people (including me) believe that you can watch your cell voltages and balance the cells manually, especially if you don’t draw too heavily or discharge too deeply. I am running similar 20 ah LiFePO4s that I got from ElitePowerSolutions.com. I am still collecting data but as an example my 24V 350W shift kit mtb used about 9ah on a hilly 13 mile ride with moderate pedal assist. The maximum amps was under 28, so I was well under the limit for 20ah 2C batteries. I find the individual cells are usually within 0.1 volt of each other off the charger and nearly dead even after some use. For instance after that 13 mile ride each cell was 3.27V. The total was 26.17V so the 24V motor still had plenty of pep. By extrapolation, I should be able to go 25 miles on a charge. Not bad for a 13 lb battery - jd
ps - in re-reading the specs on the site, these are 1C continuous/2C burst, so they're not the Yesa's I found. Still might be worth a try. Also, look into a LiFePO4 charger for best charge/longest battery life with lithium batteries
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