Help for choosing the right BMS

[DaveHT]

Hello everyone,


I plan to make several batteries of 12v each.

Each battery will contains 4 cells of LiPo4 3.2v and with configuration in 4S 12V 120A BMS (for cell balancing)

In principle I should make 9 batteries for 2 installations separately (5 for one and 4 for another one).

My question:
What brand of BMS to use that would allow me to mix these 12v batteries in series and parallel. (Can support series and parallel)

Let me explain: if I want to have 24v, I will have (2) BMS which will be connected in series

if I still want to have 12v and at the same time and increase my intensity (Amps) I would have 2 * 12v batteries so it's mean 2 BMS connected in parallel.

So please can someone tell me what type or model of BMS to use for this case; because it seems that there are BMS which do not support the connection in series and in parallel.

Thank you in advance for response guys

 

[John Frum]

Not a direct answer to your question but I can say in my experience on this forum that it is rare for diy batteries including bms to then be put in series.
Almost everyone picks a system voltage and then gets BMS(s) to match.

 

[NPhil]

I read the other day, somewhere here on the forum, that Daly doesn't support parallel on any model BMS, although they do allow 2 in series. So you're good at 24V, and, asking for a friend, I wonder what a person who has an 8S LiFePO4 back with a 24V Daly BMS paralleled with some 7S Tesla 2180 packs (which came with BMS, not sure what kind), also paralleled, which has been working tolerably for a while, should do?

 

[NPhil]

Not a direct answer to your question but I can say in my experience on this forum that it is rare for diy batteries including bms to then be put in series.
Almost everyone picks a system voltage and then gets BMS(s) to match.

I was going to do that, but I had 3 terminal BMSs, and before I got around to figuring out how to connect them in series, I found a pretty good price on 8 packs of much larger LiFePO4 cells, and decided to buy those and an 8S BMS save myself the trouble, for now. And as a bonus, the 24V BMS was only two terminal!

 

[DaveHT]

I according to you guys it's not possible to have 9 batteries 12v pack(contains 4cells). and after to connect them in series or in parallels (depends what I want)?

if you say me NOT: I will say yes it's possible because if someone buy one of this battery (see image) each of them has a BMS on it..
and as you can see those batteries are connected in series and parallels

for information about those batteries :

 

[DaveHT]

and as you can see in this picture I just want to build my own battery 12v ....in addition I want to about 9 batteries of 12v

 

[Dzl]

I don't understand why you would use two 12V DIY batteries in series rather than just assembling 24V battery packs. If you want a 24V system, and you are building your own batteries, 8S packs seems simpler, cheaper, and more straightforward. Why overcomplicate it with a series-parallel configuration and why spend extra on double the number of BMSes?

 

[MisterSandals]

(Typing slower than Dzl as usual…)

What brand of BMS to use that would allow me to mix these 12v batteries in series and parallel.

How do you plan to make 24V from the “installation” of 5 batteries?
I do not think it’s possible.

Just out of curiosity, why are you so set on 4S 12V batteries? You can halve the number of BMSs by building 4x 8S 25.6V batteries (with 4 cells left over here too).

 

[Dzl]

(Typing slower than Dzl as usual…)
How do you plan to make 24V from the “installation” of 5 batteries
I do not think it’s possible.

Typing slower but thinking better :D
I didnt stop to think that 5 batteries can't = any whole number of series pairs. Unless maybe OP wants to make 4 batteries into his 2S2P arrangement and 5 into a 5P arrangement for another project.

Just out of curiosity, why are you so set on 4S 12V batteries? You can halve the number of BMSs by building 4x 8S 25.6V batteries (with 4 cells left over here too).

 

[Dzl]

OP to stop us from speculating and guessing at things, can you explain specifically what your goal is and why you are set on 12V

 

[DaveHT]

Thank you for your answer...and my reason is simple

I will have 3 installations to make

2 of them will use an inverter 24 volts as input
and 1 inverter 12volts as input

but about 2 installations will work 7 months by year

so I want to have the possibility to change (remove some batteries on installation that not works (break time) and increase the installation that works)


Please feel free to ask me more question you want

 

[MisterSandals]

so I want to have the possibility to change (remove some batteries on installation that not works (break time) and increase the installation that works)

I like the idea of maintaining flexibility.

But, I think putting your effort (and this groups collective experience to use), you can almost certainly build the best system the first time.

So you need mostly 24V (for 24V inverter) and some 12V power?
And you are set on using 36 cells (4x4 + 5x4 cells)?

Can you explain a little about what you are using the battery power for?
And how you expect to charge them? (Solar? Alternator? Grid/shore power?)

 

[DaveHT]

Thank you for your response This is exactly the idea I would like maintained my park flexible

and when I need .. I just want the ability to move one or several batteries an put them in addition to another installation (series or parallels) and that's it

 

[DaveHT]

I find this page : https://www.mobile-solarpower.com/design-your-own-12v-lifepo4-system.html
they explain us how to connect together (Or it's possible to connect 3 BMS in parallels) if we want more loads


so to be clear I want to know what model of BMS can support series or/and parallels connection because I plan to build 9X Individual Batteries of 12v (4 cells lifepo4 per battery and one BMS on each battery)


Can someone tells me which BMS (model, #serial number should I choose ) it's supposed to be a BMS 4S 12v 120Amps or 150Amps

thank you again in advance

 

[Dzl]

I personally, have never really considered/looked into this, so I have no reccomendations, but a search shows that other people have asked similar questions to you, maybe you can find an answer in one of these posts

 

[MisterSandals]

have never really considered/looked into this, so I have no reccomendations,

Yea, I am here too. It’s way out there, unnecessarily I believe.

If you know roughy what proportion of power you need, you could build 2x 25.6V batteries and a 12V (or 3) battery(s).

It sounds like having 2x 24V inverters will be the lions share of power.

Off hand, making 4x 25.6V batteries, with 2x in parallel in each “installation” is easy and routine.

Have your 9th battery be your 12V power source.
Charge the 12V battery continually (or as necessary) from one or both large 24V banks with:

https://www.amazon.com/dp/B07D5N3XSS/

(24V to 12V, 30A)

Back of the napkin, this sounds good, close to what you describe and easy. Just 5 BMSs too.

I would look at JBD or Overkill BMSs.

 

[Dzl]

Off hand, making 4x 25.6V batteries, with 2x in parallel in each “installation” is easy and routine.

Have your 9th battery be your 12V power source.
Charge the 12V battery continually (or as necessary) from one or both large 24V banks with:

I think you may be misunderstanding part of OP's reasoning (I may be also). I think you may have misread 'change' as 'charge' in the preceding comment. There is a bit of a language barrier here I think, but to the best of my understanding, their motivation is that they will have 2 (or 3) separate systems, two of which will onlyrun ~half the year. And they want the ability to change (as in move/rearrange) batteries from the unused systems to the active system, during the other half of the year. So they are wanting interoperability/intechangeability between the 12 and 24 volt systems so they can shift batteries back and forth as they see fit. At least that is my best guess at the goal/reasons for wanting all 12V packs based on what was said above

Is that a correct understanding @DaveHT ?

 

[DaveHT]

I think you may be misunderstanding part of OP's reasoning (I may be also). I think you may have misread 'change' as 'charge' in the preceding comment. There is a bit of a language barrier here I think, but to the best of my understanding, their motivation is that they will have 2 (or 3) separate systems, two of which will onlyrun ~half the year. And they want the ability to change (as in move/rearrange) batteries from the unused systems to the active system, during the other half of the year. So they are wanting interoperability/intechangeability between the 12 and 24 volt systems so they can shift batteries back and forth as they see fit. At least that is my best guess at the goal/reasons for wanting all 12V packs based on what was said above

Is that a correct understanding @DaveHT ?

This is exactly what I want ...I am 100% agree with you Dzl


Ex: Imagine someone decides to buy about 4X 12v lifePo4 battery 100A from a seller, on depends what he needs he can :
option1: put 2X batteries in series and the 2 others in parallels to got 24v as input
option2: put the 4X batteries in parallels to got 12v

I am sure you are all agree with me in this case


now what I want (or need) is to know what is the model or serial number of this BMS inside of each battery that can support series and parallels connection?

 

[DaveHT]

Hi everyone

I am in conversation with a seller from Alibaba.com that tells me this:
.... I see. I got the news that BMS of JBD brand supports series connection and parallel connection. The quotation will be sent to you later.


can you confirm that or more details about what he says ...

 

[Dzl]

I don't know enough to confirm what they are saying, but the JBD BMS (also sometimes referred to as the 'Overkill Solar BMS' is popular here so hopefully someone will know the answer).