Top Balancing LifePo4-What's the Latest Guidance on This Subject

[Henderson]

I recently ordered 32x 280Ah cells from 18650 battery store and will more than likely order another 64 once this first set works out. My question is about top balancing. I've seen alot of varying views on this topic on this forum and on Andy's and other YT channels. I intend to have my batteries configured as a 2P16S configuration with a QUCC 250A BMS (160ma balance current) and will be using an external balancer from Neey....using their 4A 4th gen model.

I'm wondering what's the latest guidance on top balancing. Is it still recommended to setup each cell in parallel and use an external power supply, or given a 4A active balancer, can I simply set up my 32 cells into a battery and let the BMS and balancer do the top balancing for me?

Thanks

Henderson.

 

[sunshine_eggo]

same as always.

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

Make sure you actually read it. There are decision point that dictate subsequent actions.

 

[Henderson]

same as always.

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

Make sure you actually read it. There are decision point that dictate subsequent actions.

Thanks for sharing this document- it has lot's of good information.

 

[timselectric]

If that's the battery you intend to build.
Yes, top balancing would be a priority.

 

[Henderson]

If that's the battery you intend to build.
Yes, top balancing would be a priority.

Which method are you referring to? Individual cells in parallel and top balancing or top balancing using the BMS and 4A balancer?

 

[timselectric]

Which method are you referring to? Individual cells in parallel and top balancing or top balancing using the BMS and 4A balancer?

Individual cells in parallel , before building the 2p battery.

 

[timselectric]

And try to match up each 2p of cells, the best you can.

 

[Henderson]

And try to match up each 2p of cells, the best you can.

Ahhh, oh ok, I see where you're going with this. That does make sense to have each 2P cell matched indeed.- good advice, Thanks.

 

[lunatik96]

I recently ordered 32x 280Ah cells from 18650 battery store and will more than likely order another 64 once this first set works out. My question is about top balancing. I've seen alot of varying views on this topic on this forum and on Andy's and other YT channels. I intend to have my batteries configured as a 2P16S configuration with a QUCC 250A BMS (160ma balance current) and will be using an external balancer from Neey....using their 4A 4th gen model.

I'm wondering what's the latest guidance on top balancing. Is it still recommended to setup each cell in parallel and use an external power supply, or given a 4A active balancer, can I simply set up my 32 cells into a battery and let the BMS and balancer do the top balancing for me?

Thanks

Henderson.

With the larger cells, 280A, I found active balancing essential.
The BMS passive balancer is limited to 150 mA dissipation.
When I was using Fortune 100A cells, the passive BMS balancer was sufficient.
Once I started using the 280A cells, I started having a lot of imbalances and the BMS cuts off.
A single 5A active balancer has stabilized most of the over charging errors, bit it is suggested to use 3 in a 8S2P config.
My limited experience has found the larger cells are rarely matched so well that there isn't some issues, especially when going 24V or 48 V.
It is generally suggested a 5A balancer for every 200A worth of cells.

 

[Henderson]

With the larger cells, 280A, I found active balancing essential.
The BMS passive balancer is limited to 150 mA dissipation.
When I was using Fortune 100A cells, the passive BMS balancer was sufficient.
Once I started using the 280A cells, I started having a lot of imbalances and the BMS cuts off.
A single 5A active balancer has stabilized most of the over charging errors, bit it is suggested to use 3 in a 8S2P config.
My limited experience has found the larger cells are rarely matched so well that there isn't some issues, especially when going 24V or 48 V.
It is generally suggested a 5A balancer for every 200A worth of cells.

Thanks for that feedback.

 

[goldserve]

2A active balance in the jk bms is sufficient for 280aH cells. At 56.4 volts, the cells only deviate up to 60mA and these are grade B cells. I have graphs to prove it if you want.

 

[timselectric]

I would try to add as much active balancing as easily possible. In a 2p configuration, it's similar to using 560ah cells. But you don't have individual cell balancing. Any deviation of internal resistance between the paired cells will be a difference in SOC.
One cell will absorb faster than the other. One will be fully absorbed while the other has a surface charge. Which is fine if there is regularly enough floating or resting time for them to self balance. And enough balancing current to balance between the pairs.
This is why it is important to match the paired cells as closely as possible.

 

[Henderson]

2A active balance in the jk bms is sufficient for 280aH cells. At 56.4 volts, the cells only deviate up to 60mA and these are grade B cells. I have graphs to prove it if you want.

yes, would like to see those graphs, thank you.

 

[goldserve]

yes, would like to see those graphs, thank you.

Grafana

snapshots.raintank.io

 

[Henderson]

Grafana

snapshots.raintank.io

thanks.

 

[mwk1000]

I cant seem to find a US source for the neely does anyone know where an actual "neely" branded can be purchased ... I am also getting BMS shutdowns on my 280ah 2p16s setup when charging. Albia has the mfgr but quantity 5 ... ouch.

Neey 4th Gen 4A Active Balancer​