BMS recommendation for 40 cells of LifePo4 (24v)?

[camplaw]

I’m at a complete loss in terms of what BMS I need for my off grid system. I have 40x 280ah 3.2v lifepo4 cells in a 24v arrangement (5 batteries of 8 cells) giving 1,400ah.

Can I get away with just one BMS? Do I need 5, one for each group of batteries ? Does a 40s BMS exist? What amperage do I need, 100A, 200A, 300A? Really hoping someone is able to point me in the right direction as I’m hitting a major road block here. I’ve attached some more specs and information on my system and batteries if that helps! Thanks a bunch!

 

[Steve_S]

Each battery Pack gets an 8S BMS, 200A is perfect for these.
Each Battery should be Fused.
Method 1 & 2 are the most common & preferred ways of configuring the cells. #3 can be problematic especially when troubleshooting or if there is a Runner Cell in the batch.

My Suggestion / Recommendation is to use a JKBMS with 2A Active Balancer, Bluetooth, RS485/Canbus optional LCD Screen would be the
JK-B2A20S20P ref: https://www.aliexpress.com/item/1005003104573871.html NB: HankZor is the one who does the Docs, the IOS/Droid Apps and more. Link to Manual: https://github.com/NEEY-electronic/JK/blob/JK-BMS/JKBMS INSTRUCTION.pdf and there is much more on that Github Link as well.

 

[camplaw]

You're a life saver! Thank you for the insight and information. As for the model of BMS could you explain the difference between the B2A20S20P and B2A8S20P? If I need one BMS per group of 8 cells would the B2A8S20P not do the trick? Trying to not break the bank if I can and they're about $100 difference in price. Maybe I'm missing some important information here

 

[Steve_S]

Yes, that one is Almost Identical to the one I posted except it is only capable of 4S-8S and should be just fine. I was thinking 16S for some reason when I posted above. - In the midst of painting my house & a bit sleep deprived... LOL
They are shipped with an ON/OFF Switch now I believe. But if you get Jikong BMS RS485 CAN module and LCD display Adapter it also has a switch and can display vital info at a glance.

10.0US $ 1% OFF|Jikong BMS RS485 CAN module and LCD display Adapter|Battery Accessories & Charger Accessories| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

NOTE There are 2 displays, select this one for that model of BMS.
$46.44 USD

 

[camplaw]

That makes sense, perfect thanks! The other thing I was questioning was whether or not it would work for me to to get 5x 100A rated BMS's and run them in parallel together make 500A total. I was looking at this BMS as well:

8s BMS 100a LifePo4 with 12″ 8ga Wires – Overkill Solar

overkillsolar.com

I don't know enough about split phase systems to make an educated decision. I have two 3000VA Multiplus units running split phase, does that give me 6000VA then? Would 5x 100A BMS's in parallel be enough wattage and protection? Chances are I'll go with the BMS you recommended, just want to check all the options and which is the best route to take and I feel ya with the whole lack of sleep lol get some rest. And I hope your painting goes smooth (I used to run a painting business, I can relate to how painful it can be).

 

[Steve_S]

The batteries with 280AH Cells can output 280A for 1 hour.
Better off with 200A BMS' to get what you can when a surge or heavy load comes AND they will !
TBH, 100A is peanuts. Says the guy with 5 packs, 1190AH / 30kWh of battery...

As for Sleep/Rest, my Doctors would have a kinipshin, I just spent 3 weeks in ICU & Thorasic Critical Care and have only been "free" for a short while and am supposed to be resting to recover from everything I went through. Let's just say, that I had a Very Close up & Personal cheek to cheek dance with the Grim Reaper and walked away ... was only a couple of hours from seeing the other side...

BTW: Download THIS Resource, you will find it very handy to have.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

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