Measuring Battery Capacity (48V)

[someguynamedbob]

I have an existing 48V battery and I just ordered a new 48V 12Ah battery from aliexpress

I would like to measure their actual capacity (Ah), without disassembling to their individual cells

I was originally looking at the IMAX B6 but it seems it can't measure voltage that high

Would something like this help me to determining the actual capacity: http://www.ebay.ca/itm/Digital-60V-100A-Battery-Balance-LCD-Voltage-Power-Analyzer-Watt-Meter-New-/330954111370?pt=LH_DefaultDomain_0&hash=item4d0e66f98a&_uhb=1

Any better/cheaper ways to do so?

 

[dnmun]

the only way to do it correctly is to actually measure it. accurately.

to measure it you have to charge each cell up to 3.65V somehow and then when they are all full you discharge the pack into a dummy load. i used space heaters, the oil bath type, and radiant floor heaters.

discharge at .1C for lead acid specs, and most people discharge the lifepo4 at .2C-.4C from full charge down to the point where the first cell hits the LVC point on the BMS at 2.0V with a wattmeter or you can use an ammeter on your voltmeter and a clock but a wattmeter is easier to use.

 

[dogman dan]

That's about the cheapest wattmeter out there. Once you have it installed, you can discharge into a heater, bunch of light bulbs, or even just go for a ride that is long and steady with few stops.

If you want to know what your 1c capacity is, then it's pretty easy to go for a 1c ride. 12 amps discharge rate for a 12 ah battery is 1 c. But if you want to keep your discharge rate at 1c, it will help to know what your real world capacity is.

Have that wattmeter on the bike all the time, and you can track variations in capacity in rides of differing speeds, and get a better idea of what is easy on your battery and what is ruining it. Try to ride at 1c as much as possible, and avoid 2c rides up long hills.