Experimental question on charging

[Solarfun4jim]

If you had two identical setups, using the same pv panel input and same SCC's, but you set one up to charge at 3.65v/cell and the other to charge at 3.4v/cell, but both had their charges terminated by a BMS exactly when their respective first cell hit of 3.4v, what would be the expected difference in SOC up to that point.
(note: not saying it is good practice to use a bms to terminate like this, but for the sake of experimental outcome).

Would both SOC's be very similar, or would you expect the one charging at 3.65V to be somewhat significantly higher?

 

[RCinFLA]

You are putting the same AH's of charge into all series connected cells up to point of charge termination, unless a balancer on a cell kicks in to bleed excessive charge to the cell that balancer activated.

Final state of charge depends on charger amperage rate, where they started from, plus any balancer modification. Other variable is matching of cells for their individual capacity and internal impedance.

Higher charge current yields less state of charge at a termination of 3.4v. Very low charge rate would yield about 99% SOC, a 0.3C to 0.5C charge rate would yield 80-85% SOC at 3.4v termination.

The amount of kinetic overhead voltage created during charging is greater the greater the charge current it is supporting. The kinetic overhead voltage (times charge current) is the overhead power (loss) required to create and move ions within the battery. There will also be some loss due to cell impedance. At 0.3C to 0.5C charge the loss due to impedance and loss due to kinetic energy is about the same for a good quality cell but depends on quality and age of cell. Poor quality cells may have higher impedance by their internal design.

 

[Solarfun4jim]

You are putting the same AH's of charge into all series connected cells up to point of charge termination, unless a balancer on a cell kicks in to bleed excessive charge to the cell that balancer activated.

Final stage of charge depends on charger amperage rate, where they started from, plus any balancer modification.l Other variable is matching of cells for their individual capacity and internal impedance.

Higher charge current yields less state of charge at a termination of 3.4v. Very low charge rate would yield about 99% SOC, a 0.3C to 0.5C charge rate would yield 80-85% SOC at 3.4v termination.

The amount of kinetic overhead voltage created during charging is greater the greater the charge current it is supporting. The kinetic overhead voltage (times charge current) is the overhead power (loss) required to create and move ions within the battery. There will also be some loss due to cell impedance. At 0.3C to 0.5C charge the loss due to impedance and loss due to kinetic energy is about the same for a good quality cell but depends on quality and age of cell. Poor quality cells may have higher impedance by their internal design.

Fantastic mate. Great way of explaining things.