Charging 14s pack with 13s charger

If I were to charge a 14s pack with a charger built for 13s (54.6V), any idea how much capacity would I be giving up? Is there any problem/danger doing this? I assume each cell would be at about 3.9V instead of 4.2V.

I realize I will need to periodically charge with a 52V charger to balance the pack.

dilkes said:

If I were to charge a 14s pack with a charger built for 13s (54.6V), any idea how much capacity would I be giving up? Is there any problem/danger doing this? I assume each cell would be at about 3.9V instead of 4.2V.

I realize I will need to periodically charge with a 52V charger to balance the pack.

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The only "problem" will be the highly increased cycle life)) And you don't need to periodically charge with a 14S charger to balance - you just need to connect a 14S LiFePO4 balancer after charging with a 13S charger to balance the cells at 3.6V. But it will take a long time to get them discharged from 3.8-3.9V down to 3.6V.

It is possible you'd be leaving over 20% of capacity on the table. A pair of precisely timed CC load discharge tests will give you the accurate number.

Longevity would be better served charging to 4.05-4.10V, and leaving that 20% sacrifice at the low end, shallower average DoD.

Balancing is best done at the top end in that situation, just above where you stop-charge in normal use, well into the voltage rise "shoulder". Many ways to skin that particular cat, including BMS that let you adjust their start-balance voltage lower.

Most do need a lot of time to do their work.

Balance at full charge, the 14s charger if your pack has a bms.

Then to increase cell life, discharge again at least some right away. Its time full that damages more than a brief time full for balancing. At 3.9v, it won't balance near as accurately, even if you use a balancer you can set to that voltage. Yes, you could balance at 3.6v closer to bottom, but the main thing you want to avoid by balancing is an overcharge. That won't happen at 3.9v, so no worry about that happening.

You will lose a lot of capacity, fine if you don't need it at all, like you ride 6 miles a day and charge. A ride that short you could get away with using a lame lead battery.

I agree, if your losing 20% at the top means a deep discharge, leave only 10% or so at the top. Look into if you can turn up the 13s charger a bit, and get to 4v per cell at least.

Best way to balance IMO, is single cell charging any low charge cells. I use a cheapo RC charger for this. This will work fine if you don't have a bms, but have a balance plug on the pack.