Electric Bikes - Converting to LiFePO4
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06-22-08, 03:58 PM
Can anyone tell me if I can use 36Volt 20 amp LiFePO4 batteries with a 36 volt 600 watt motor with 50 amp controller?
Thank you for your help.
06-22-08, 04:23 PM
OT I like your icon.
06-22-08, 06:15 PM
Can a senior member from california give me help is it possible to use these kind of batteries with my 36 volt 600 watt 50 amp unit, will it work okay?
Thanks for the help.
I can try to help.
Short answer to your question - yes, I think so.
What you need to know is how your battery will behave if your controller "asks" for 50 amps. If you ever go up to full throttle, it's likely your controller will "ask" for the full 50 amps if it's designed as a "50 amp, at peak current" controller.
Many LiFePO4 batteries have a current limit feature built in to the battery management circuit at "2C" meaning you multiply the amp hours by 2 to get the amps it can put out. Batteries from ebikes.ca, LiFeBatt, DeWalt, and a couple others, may be able to tolerate much higher current than that.
So your battery might be limiting itself to 40 Amps. This is probably fine - I think your battery won't blow a fuse. I think it'll just send out 40 Amps and no more if it gets "asked" for more than 40 amps, or else it'll cut out when you ask for more than 40 amps and come back on when you unplug it.
One thing you should be aware of is that to get the wattage (power) that a motor+controller combination are consuming, you multiply the controller's Amps by the Volts. So 36V times 50A = 1800 watts as "peak" power. Motors are often rated in terms of "continuous" power which is less than peak power, but it's usually something like 66% of the peak power, which would be 1200 watts in your case.
If you never use "full" throttle while your bike is moving very slowly, you might never go above 40 amps anyway.
06-22-08, 07:35 PM
Thats great! thank for your help I can now get a light weight battery set.
Thanks a bunch.
06-22-08, 09:12 PM
I am from California, but I am not a senior member.
I cant help.
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