Advice on better quality BMS

Marcus_swe

New member
Joined
Sep 15, 2018
Messages
5
Hi,

Im pretty new the DIY powerwall scene and I need advice on a good quality BMS for my powerwall build. Im buying a EAsun hybrid inverter and the battery voltage is 24v so Im planing to build two7s20p batteries from brand new panasonic 2900mah 10A 18650 cells. And to go with that I need a BMS , Im looking for somerhing in the 50$ - 100$ price range. Batrium is too expensive.

Thanks in advance for your input
 
Marcus_swe said:
Sean said:
How much are you spending on the cells and inverter ?

The cells are 728 and the inverter is 350

That's a fair sum to spend, you might want to consider spending a fair bit more on the BMS to protect your investment.
 
Batrium is what I run. I got 4 of em so :)


The protection should be very important since thats what will save you in the end. There is BMS systems for 50-100USD but are they good enough? Do you know what functions and type of protection you want and or need?
 
I got mine direct from batrium was delivered within the week via DHL

if you really want to get your hands dirty a member on here had a DIY solution for BMS
I did look at it and think for my 18650s will give it a go
 
I use two. But they're not BMS. They're just balancers (although one I did turn into a BMS through my own hack). My take is if you already monitor your cells closely enough, have good cells (new or closely matched) then you're really not going to run out of balance that quickly. I have my batteries outdoors now and I monitor them once in a while.

QNBBM 1S - They're relatively expensive for what it does. If you don't plan on expanding past 7S then maybe an option. At 14S it's pricey. I used two of these and manually balanced my 7S. But if you want to automatically balance, you will need to get 7 of them at $20usd/pc.
https://www.aliexpress.com/item/lit...oltage-difference-within-10mV/1768384410.html

Active balancer - This works up to 14S. Seems to work for me. I hacked the output to send to influxdb and monitor through grafana. Been running for 6 months now. It only really balances when over 30mV and if the pack is too large, it may take a while. My packs are pretty good in staying balanced so it works well. Around $100usd/pc.
https://www.aliexpress.com/item/5-1...ion-control-module-upper-and/32767618479.html

I also noticed this while looking for links but have no clue on how it works.
https://www.aliexpress.com/item/5-1...ion-control-module-upper-and/32767618479.html
 
Marcus_swe: I will be taking care of that in EU some day when the stock is large enough. If you live close to me come and visit me :) I might even have 1 unit to spare of WM1 if its for interest.
 
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