Help me choose the right BMS for these systems

[Tiktaalik]

Newbie here and I just order a set of 20 Lishen 272Ah LiFePO4 cells two build two separate battery configurations. One will be a 12v - 4S (4 x 3.2v cells) bank and the other will be a 24v - 8S2P (16 x 3.2v) 544Ah bank. I am looking at buying a Heltec BMS for each of these systems. Would the two with the red checkmarks in the attached image work? I'm not sure what the difference is between all these and what I ought to be looking for. Is it possible to use one BMS for all 16 cells of the 8S2P config or do I need two BMS units? Do I need a Smart BMS? Thank you!

 

[DThames]

If the charge and discharge amps are within a range that you are happy with, one BMS for a 2p8s would be okay. 8s2p describes two strings joined in parallel, which would require 2 BMS.

 

[Tiktaalik]

If the charge and discharge amps are within a range that you are happy with, one BMS for a 2p8s would be okay. 8s2p describes two strings joined in parallel, which would require 2 BMS.

Ok, thanks! I wasn't sure of best practices for the larger bank. Can all 16 cells be a series connection? Should they be? Which way is preferable?

 

[Tiktaalik]

What charge/discharge amp rates should I be looking for, for these configurations?

 

[Tiktaalik]

If the charge and discharge amps are within a range that you are happy with, one BMS for a 2p8s would be okay. 8s2p describes two strings joined in parallel, which would require 2 BMS.

I heard back from Heltec and they said that the BMS units I posted a picture of are not their own but that they still sell them. They also said that the Amp rating for those (300A) is peak, not continuous. Can someone educate me on the difference? How do I determine what Amp rating is appropriate for my specific system?

 

[Tiktaalik]

For my 4S - 272Ah - 12v array for example, will a 120Ah continuous charge/discharge BMS like this one work?

For my 8S2P - 544Ah - 24v array, will this one be sufficient?

Is it based on the calculated load or the Amperage rating of the battery or...?

Thanks oh mighty hive mind!

 

[DThames]

For my 4S - 272Ah - 12v array for example, will a 120Ah continuous charge/discharge BMS like this one work?

For my 8S2P - 544Ah - 24v array, will this one be sufficient?

Is it based on the calculated load or the Amperage rating of the battery or...?

Thanks oh mighty hive mind!

For example, if you have a 3000 watt inverter on a 24v battery, you might be pulling 3000/24=125 amps plus some surge. The BMS needs to handle the amps of your load. Also BMS will have charging limits, so must handle your charging amps as well.

 

[Tiktaalik]

Ok! Thank you! This is very helpful.

So it is dependent on both on the capacity of the inverter as well as the charging amps? How do I find out what my charging amp capacity will be? Is that based on my load calculation?