Why there is no 12/16S 12V BMS(LifePO4)?

[tezcanibrahim]

I'd like to make 4s3p(12V) battery bank for my campervan conversion. Is there 12/16S 12V bms? How can I connect these 12(280ah LiFePO4) batteries with only 1 BMS? Thank you for your help!

 

[Bob B]

Doing that would require that you do a 3P4S configuration ..... 4S3P would require 3 separate BMS.

I did 2P4S with mine.

Is it necessary to keep them all in a long row .... or would a more rectangular shape work? What are your current requirements?

 

[tezcanibrahim]

Doing that would require that you do a 3P4S configuration ..... 4S3P would require 3 separate BMS.

I did 2P4S with mine.

Is it necessary to keep them all in a long row .... or would a more rectangular shape work? What are your current requirements?

Bob, thank you for your reply! The BMS only has 4 positive leads. This means that you are not monitoring individual cells. You are monitoring a group of cells that equal about 3 volts. Yeah? How does the BMS know if 1 cell in that group of 3 is more or less charged?
The space is not an issue. I can change the configuration to 3P4S.

 

[Bob B]

Bob, thank you for your reply! The BMS only has 4 positive leads. This means that you are not monitoring individual cells. You are monitoring a group of cells that equal about 3 volts. Yeah? How does the BMS know if 1 cell in that group of 3 is more or less charged?
The space is not an issue. I can change the configuration to 3P4S.

You will only know the voltage of the group .... If that doesn't work for you, you will need to do 3 independent packs each with their own BMS and then put them in parallel.

 

[Rocketman]

Look at Batrium - expensive- but can handle as many cells as you want.

 

[tezcanibrahim]

You will only know the voltage of the group .... If that doesn't work for you, you will need to do 3 independent packs each with their own BMS and then put them in parallel.

If I go with the 3P4S configuration, can use an active battery balancer with the BMS? Is group monitoring safe? I just don't want to damage the cells nor cause a fire. My apologies if these questions sound stupid, it is because my electric knowledge is pretty much non existing.

 

[Bob B]

If I go with the 3P4S configuration, can use an active battery balancer with the BMS? Is group monitoring safe? I just don't want to damage the cells nor cause a fire. My apologies if these questions sound stupid, it is because my electric knowledge is pretty much non existing.

There is a limit to how many cells can be paralleled ..... it also depends on the cells themselves and how well matched they are.
I have no problems yet with my 2P4S pack .... but they were pretty well matched cells to begin with.

Everyone has to judge their own situation, pack use, current needs, etc, etc ..... to determine what will work for them. If it doesn't work well .... go to plan B.

 

[DLTooley]

You could try the 3p4s configuration to get going if you are confident of the quality of your cells.

In any case, you will want to check individual cells periodically. Upgrading your BMS at a later date as needed and budget allows seems like an ok plan to me.

 

[tezcanibrahim]

You could try the 3p4s configuration to get going if you are confident of the quality of your cells.

In any case, you will want to check individual cells periodically. Upgrading your BMS at a later date as needed and budget allows seems like an ok plan to me.

The batteries are brand new cells and flat as a pancake on all sides, no puffing anywhere. The initial voltage was precisely 3.329 on all 12cells. I guess, I'll try the 3p4s + 250amp Daly BMS configuration.

 

[time2roll]

Diagram here:

https://diysolarforum.com/threads/busbar-help-for-my-bank.21383/

Can also go in one long stack if you prefer.

 

[DLTooley]

I would suspect that as the batteries get older the likelihood of divergence would go up.

 

[time2roll]

I would suspect that as the batteries get older the likelihood of divergence would go up.

I believe the real risk would be if 3 best cells were together and 3 worst cells were together.
In all probability there should be a mix to average things out.

 

[mitiempo]

The batteries are brand new cells and flat as a pancake on all sides, no puffing anywhere. The initial voltage was precisely 3.329 on all 12cells. I guess, I'll try the 3p4s + 250amp Daly BMS configuration.

Did you top balance? Results?

 

[Scph9002]

Bob, thank you for your reply! The BMS only has 4 positive leads. This means that you are not monitoring individual cells. You are monitoring a group of cells that equal about 3 volts. Yeah? How does the BMS know if 1 cell in that group of 3 is more or less charged?
The space is not an issue. I can change the configuration to 3P4S.

Dont need to worry it is exactly same charged as the other cells. That is what happens naturally when they are in paralell.