Battery balancer wiring for 24v 8s2p.

[Antony22]

Hey everyone.

I have a 8s2p 24v lifepo4 battery, B grade cells. I'd like to use a balancer to increase my capacity as one or two of the pairs of cells are discharging faster than the others.

How shall I approach this? I tried an 8s balancer, but I don't think it could cope with my 2p pairs of cells as their combined voltage was higher than the operating voltage range of the balancer. If I use a 16s balancer it won't be able to read every other cell correctly. Any sugestions would be greatly welcome, many thanks!

 

[sunshine_eggo]

Hey everyone.

I have a 8s2p 24v lifepo4 battery, B grade cells. I'd like to use a balancer to increase my capacity as one or two of the pairs of cells are discharging faster than the others.

8S2P usually means two 8S batteries (25.6V) in parallel, each with their own BMS.

How shall I approach this? I tried an 8s balancer, but I don't think it could cope with my 2p pairs of cells as their combined voltage was higher than the operating voltage range of the balancer.

This doesn't make sense. 2P cells have the same voltage as a single cell, or you're doing something very atypical.

If I use a 16s balancer it won't be able to read every other cell correctly. Any sugestions would be greatly welcome, many thanks!

Need more info.

BUT...

You likely have a bad cell in the misbehaving pair. It's losing charge and drawing current from the good cell (or both are bad). No amount of balancing can keep up with or correct this condition.

 

[time2roll]

Most of these balancers are very low amps compared to the typical load and will not keep up real time during a single discharge.
May help some but not going to really fix a capacity issue at the cell level.

Possibly the cells are a bit out of balance for a multitude of reasons for which the active balancer will help over time.

 

[ZEUS-FL]

@sunshine_eggo "8S2P usually means two 8S batteries (25.6V) in parallel, each with their own BMS."

I am new in the forum. When you say 8S2P each with their own BMS? what do you mean? I have a pack with the exact same configuration but I am using only 1 8S BMS and also 1 8S active balancer. Yes they are 16 cells but still balance 2 cells as 1. is this correct?

Or do you have a better way to do this by using 2 BMS connecting 1 cell per BMS? I get lost with this.

 

[sunshine_eggo]

@sunshine_eggo "8S2P usually means two 8S batteries (25.6V) in parallel, each with their own BMS."

I am new in the forum. When you say 8S2P each with their own BMS? what do you mean? I have a pack with the exact same configuration but I am using only 1 8S BMS and also 1 8S active balancer. Yes they are 16 cells but still balance 2 cells as 1. is this correct?

Or do you have a better way to do this by using 2 BMS connecting 1 cell per BMS? I get lost with this.

Literally two separate 8S batteries in parallel.

The convention 'round these here parts is order of operation... you put cells in 8S first, then two in parallel 2P. Same with solar panels and with battery banks.

If you have a battery with EIGHT groups of TWO parallel cells forming a single cell, then those cell groups in series, that's 2P8S - order of operations... you build your 2P groups and then you place your 8 2P groups in series.

 

[ZEUS-FL]

Literally two separate 8S batteries in parallel.

The convention 'round these here parts is order of operation... you put cells in 8S first, then two in parallel 2P. Same with solar panels and with battery banks.

If you have a battery with EIGHT groups of TWO parallel cells forming a single cell, then those cell groups in series, that's 2P8S - order of operations... you build your 2P groups and then you place your 8 2P groups in series.

I understand that but you mentioned each one with their own BMS. I may miss understood what do you mean but I guess you refereed 2 separates BMS? or you are still talking about use 1 single bms?

 

[sunshine_eggo]

I understand that but you mentioned each one with their own BMS. I may miss understood what do you mean but I guess you refereed 2 separates BMS? or you are still talking about use 1 single bms?

Yes. Again, 8S2P is literally two separate 8S batteries in parallel. Each with its own BMS.

Let's put it all in one place:

8S2P = two separate 8S batteries in parallel (like how you parallel 12V - only at the ends), each with its own BMS.
2P8S = ONE 8S battery with each "cell" comprised of 2X parallel cells - ONE BMS.

Clear?

 

[ZEUS-FL]

Yes. Again, 8S2P is literally two separate 8S batteries in parallel. Each with its own BMS.

Let's put it all in one place:

8S2P = two separate 8S batteries in parallel (like how you parallel 12V - only at the ends), each with its own BMS.
2P8S = ONE 8S battery with each "cell" comprised of 2X parallel cells - ONE BMS.

Clear?

Ohhhh I just learned something new. I do not know that concept. Is more efficient using 8S2P then with 2BMS? instead 2P8S because then that is my configuration. That will means 8S2P will be each cell controlled and easy to identify when you have a bad cell when in 2P8S will be more difficult to identify. I got the concept now. Is that right?

 

[sunshine_eggo]

Ohhhh I just learned something new. I do not know that concept. Is more efficient using 8S2P then with 2BMS? instead 2P8S because then that is my configuration. That will means 8S2P will be each cell controlled and easy to identify when you have a bad cell when in 2P8S will be more difficult to identify. I got the concept now. Is that right?

Yes. You also have more redundancy with 8S2P... if you have a problematic cell in one battery, you can just take that battery offline and still have an operational battery in a few minutes.

 

[ZEUS-FL]

I got it. Thank you very much for the information, it completely make sense. Excellent for operation critical situations like medical equipment ect.. Maybe overkill for house, but I like overkill LOLLL is just 1 more BMS and few things but I like the fact you can have total control of the cells.