diy solar

diy solar

12v BMS design. What would you like to see

The philosophy of this design is in my case with 3x 4S packs , I have in effect three completely redundant battery systems each with it own BMS and local safety disconnect contactor. Even though the three can act in cohort , each one can also function without the others.
I do like this approach.
 
I do like this approach.
Yes I think it offers the best chance of redundancy.

There is an overall and rather unjustified fear that LFP “ will let you down “ unexpectedly. In reality your LA tech was likely to fail first. But everyone hears “ lurid” takes of Lithium failure and the “ nonsense “ gains ground

In this case I have the ability to degrade battery by battery each degradation looses me 100AH. So what.

I spent today reading the ATMega406 120 pages of docs to understand the chip. It has its drawbacks ( it can’t drive N channel disconnect fets. ). I also ordered some 200A 60v 0.75 milliohm Rds N channel mosfets. But I’ll have to design in a seperate N channel get voltage booster circuit to use then as the 406 expects P channel.

The issue is even at .75 mill ohm you have Watts of heat to conduct away
 
30w x 3.41 w/btu/h = 102.3 btu/hr not that much really.
 
I think the cell level bms is a very interesting I could seperate out the active balancer as this is a seperate module per battery

There is a ATTINY cell based open bms project already
Maybe 4-packs on a board would be easier to work with.
 
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