It seems that the battery capacity has decreased

After several weeks not using the E-Bike, we have discovered an (aparent) important lost of capacity in the battery.

The logical hypothesis is that the cells are unpaired.
This means than the 16 serial battery needed to give the nominal 48 volts have diferrent electric charge.
Then when we discharge (using the bike) the battery:
a) When the cell less charged arrives to the minimum admited voltage. The BMS (battery management system) cuts the power. But there are still cells with near 50% of residual charge.
b) When we recharge the battery, the cell with more charge arrives to the maximum admited voltage. The BMS cuts the power. But there are still cells charged near of the 50% of its capacity.

But this 'never-end loop' has a solution:
The battery charger during the charging process gives a current of 2.6A but it really doesn't cut totally when the most charged cell reaches the max cell voltage. Then it just gives a standby current near 0.085A.
This means that this standby current doesn't overheat the already loaded cells, but let the not full charged cells arrive to be loaded. This process will pair again the cells.

What is the problem:
This is a slow process for a 20AH battery. If our battery has some cell charged at 50% of the other, this means that we will need to recharge 10AH with a source of 0.085A.
In other word we'll need 117hours (near 5 days) to finish the process.
By now we have recovered 2.5A, we will need to be patient.

Lesson learned: If you don't use the E-Bike for a long time, connect the charger at least 24h every 2 weeks ;)


BMS example:
http://www.conhismotor.com/ProductShow.asp?id=132