diy solar

diy solar

Batrium BMS setup 8s3p

I run 2 Batriums - so I can see what's happening in my home powerwall packs and in my trailer. Balancing is misunderstood (in my opinion) and leads to long discussions about 'active balancers' and other topics. The key thing is that healthy cells (no self-discharge) that are well matched in capacity (within 2-5%) do not need much balancing. Its amazing - but its absolutely true.

For example, I have 84 packs @ 260ah each made of a variety of 18650 cells. Here's this morning's Batrium pic - .05v (50milli-volt) max difference:
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The last touch-up balance I did was on March 22, 2021 (4 months ago) using auto-level to bring 20milli-volts back in to 0.04v max difference in the morning. The battery bank has charged/discharged 4,391kwh over those 4 months. It's 'drifted' up from 0.04v to 0.05v over that time. After another few months and it reaches 0.06v - I'll do a touch-up using Batrium auto-level balancing (can run at any voltage).

I could try for 0.02v or 0.01v max difference in the balancing... but it doesn't add anything to my operation and reaches a point of overkill. If they start at 0.04v max difference in the morning they may diverge up to 0.07v max thru the day but right back to 0.04v max difference by next morning. If forced it to 0.01v max difference - it would just diverge up to 0.04v during the day and then back to 0.01v.

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After selecting "Auto Level" click the More button to the right of the drop-down to get this popup....
View attachment 57189



Here's the trailer Batrium - 0.02v max difference. No balance since last Feb and not likely to need any soon. Its 14s88p of all the same cells. As above - I didn't try to get any closer than 0.02v max difference when I originally balanced.
View attachment 57185
Thank you for the information that is well received on my end! I am still fairly new to a lot of these things. My Batrium is here but my batteries have not arrived yet. So I have not been able to charge, test, balance or even know the “actual grade” of batteries I paid for. However once I get everything together and up and running I may need some advice on the Batrium set up and settings to make sure my system operates as well as your seems to.
Its my understanding that if you have reasonably conservative settings and operate in that 85% to 15% range of your battery capacity that you will not have runaway cells. I do not know how my system will react when I get it under full load. It just seems from what I read and a lot of these threads, people do not get very well matched in balanced cells and seem to have runners that active balancer helps maintain.
That doesn’t mean that there isn’t some other problem that is causing the runners under high load conditions. My intention was to set everything up without any sort of active balancing and try to find tune it from there.
 
It’s good to know and I appreciate the information. Makes me feel better....I was thinking about ordering active balancer and just having them on hand just in case I were to need them at some point.
I’m using the Sol-Ark 12K, what inverter are you using?

Victron Multi 3000/12-120.
 
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