Building LiFePo battery from eBay cells

[bapman007]

I am pretty green at ebikes and battries and I am learning as i go...

there is a seller on ebay selling 12v 20aH flat cells (like the size of laptop dock), they are reated at 1C.

I was wondering about combining 4-5 of these cells into a 48-60V pack. They would fit perfectly into the recumbent frame I have and can be (physically)separated (but electrically act as a single battery) on the bike for weight distribution.

The question I have is the 1C enough? I want to be able to go 25mph or so on a 26" geared hub motor. Would i need a BMS for a 4-5 cell setup like this?

Thanks ES.

 

[biohazardman]

Buying a 1C, that's peak amperage the seller states, battery will likely leave you with a bad impression of the LifePo4 chemistry when it can be a very good thing. Yes, it would need a BMS as will most low C rate batteries to keep them from being damaged from being pushed over their amperage limits. I would suggest at least 1.5-2C and more is even better. The battery described will give at most 10-15 amps of usable power. I would suggest Ping, Cellman, ebikes.ca/Grin cyclery for your battery. Your battery is the most important and quite often the most expensive part of you ebike. If you are going to lug 20-25lbs of battery around at least make sure it can pull it's weight.

 

[dogman dan]

At 20 ah size, a 1c cell can work ok. My first ping had 1c cells. But those were "good" 1c, able to tolerate 2c peak. If it's 1c peak, then you'd need about 40 ah of it to run 20 amps continuous.

A bms is highly advisable, but it's not impossible to get good results without it. It's just a PITA, since you have to be the bms yourself. As a rookie, the chances of your making a mistake that ruins the pack is very high without a bms.

So plan on getting a bms, if the 12v pack allows access to the individual cell terminals.