Have you ever thought of doing a simple monitor? Just turn on a light if a cell is low. And I feel that it is worth asking, why monitor all the batteries if you know they are from the same vintage, source, and condition? Why not watch them from a higher level, say, 2S, 5S, 6S, 10S (some even integer of your total string).
Oh, alright. Maybe I misunderstood what the picture is.
From my perspective, I dont care which one is low. I have been warned that something is fishy so I will look into it after I lift the throttle. A big angry red led on the dash board would be enough of a warning. Automatic systems are nice and all, but if they aren't working right then you will toast it all anyway (like so many cheap BMS out there already).
My concern is cost and requirement. I would rather know there is a problem and take care of it than have the system just shut down on me. Plus with a monitor there is less chance of something going wrong.
I do like the idea of contactor isolating the packs though. But what if the packs sit for a while and level out to different voltages?
Very cool! Glad you have thought all this out. I saw this thread and thought it could help me out. I have those Fiat 500e samsung/Bosch modules that are blocked together in 5S modules. I have three strings of 6 modules (ends up being 30S3P) at 64Ah per cell. As I just introduced my second pack I've been wondering what best path to take to help isolate them. But also, since these are blocked together from the manufacturer, each module should have identical cells so why not just watch the 5S module. The end result would be the same, the system automatically shuts it down or turns on a light and I have to figure out what is going on.
So when you charge, does the contactor closes if the battery voltages are the same or within allowables?
Note: I also work aviation electrical but from modification standpoint. The aircraft systems are designed to automatically load shed in the case that a generator is lost or overloaded. But this system is backwards from how we do it in a car since your system shuts the battery down instead of the load (although you did say this could talk to the controller).
So what power controller are you using? And are these Leaf relays easy to get (I can't seem to find them on a quick search)? This all seems way more than i intended to do with my build. I'm using a "dumb" Kelly 12600 controller, a TSM2500 CAN charger, and these Fiat batteries. As simple as you can get compared to what you have created!
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