battery charging and c measurement

[good]

I just began charging a 12v 230ah LiTime LiFePo4 battery with a 40A LiTime charger. Everything seems to be going smoothly (battery started off at 50% SOC). But the charger started reading about 1.25c and has been steadily increasing (now over 20.0c). I am sure that I am seeing the decimal point correctly. Does this make sense? Is it likely the charger is simply putting the decimal point in the wrong place?

 

[sunshine_eggo]

I just began charging a 12v 230ah LiTime LiFePo4 battery with a 40A LiTime charger. Everything seems to be going smoothly (battery started off at 50% SOC).

You can't trust SoC on a new battery until it's been charged to full. Hazmat regs mandate batteries not ship at > 30% SoC, but it's pretty common to find them in the 30-50% range.

But the charger started reading about 1.25c and has been steadily increasing (now over 20.0c). I am sure that I am seeing the decimal point correctly. Does this make sense? Is it likely the charger is simply putting the decimal point in the wrong place?

Nothing about this makes sense.

C?

°Celsius?

C rate?

If °Celsius, the charger is likely reporting its own internal temperature. 1.25°C indicates it was a little above freezing. 20°C indicates the charger is warming itself.

C rate is a function of capacity. Your charger is only capable of 40A, so C rate will not exceed 40/230 = 0.17C.

If it's tracking input, it should report Ah directly.

 

[good]

You can't trust SoC on a new battery until it's been charged to full. Hazmat regs mandate batteries not ship at > 30% SoC, but it's pretty common to find them in the 30-50% range.



Nothing about this makes sense.

C?

°Celsius?

C rate?

If °Celsius, the charger is likely reporting its own internal temperature. 1.25°C indicates it was a little above freezing. 20°C indicates the charger is warming itself.

C rate is a function of capacity. Your charger is only capable of 40A, so C rate will not exceed 40/230 = 0.17C.

If it's tracking input, it should report Ah directly.

So according to the charger instruction sheet, c refers to "the capacity that has been charged to the battery (not the current capacity of the battery)." The battery has bluetooth and the app shows what appears to be normal charging (40.7A current, 13.5V, 151.8Ah). The temperature of the battery has risen slightly and is now at 69.8F. The battery and charger are cool to the touch.

 

[sunshine_eggo]

So c = Ah, and 20.0c means it has input 20Ah into the battery. Would expect a charge to take you between:

230Ah * .7 / 40A = 4 hours
230Ah * .5 / 40A = 2.9 hours

It may take a little longer due to absorption time, and the 40A claim is probably not 100% accurate, i.e., might actually be a little lower or even higher.

If connected with alligator clips, there will be losses, so that can increase the charge time too.