I've read through this, wow this is a lot of great info. I came across a pair of U27-XP's that I'm planning on using in parallel with an inverter/charger to function as essentially a high-capacity UPS. I'm trying to figure out how much of the "non existent BMS" functionality I actually need to worry about. I've gotten as far as the following... would love comments or corrections here.
Set the charger profile for 14.4v / 13.6v. This is narrower than the spec for the batteries, I'm not terribly capacity constrained and they're old cells so I'm not concerned about squeaking every last Ah out of them.
Set the inverter low-voltage cutoff at 10.5v. I don't expect these batteries to be cycled often at all (other than periodically where I'll have control of it) but even a cutoff at 10.5 should be sufficiently high to keep the batteries in decent shape, without the internal BMS needing to be present.
Speaking of the internal BMS, is there much value in dealing with the effort of getting it up and running? I've read tons about the laptop and talking to it and reading data from the cells -- this is all very cool but goes on my "one day" list, not on the "day one" list of stuff to do. So my questions...
1) is it safe / sane to just leave these with their internal BMS in sleep mode persistently, given that I have high and low voltage cutoffs in the inverter, and they'll be in a temperature controlled environment?
2) is there a trivial way to keep the basic sanity checking parts of the internal BMS up and running without doing all the USB/RS485 stuff? From reading through this, it MIGHT just be as simple as "plug the batteries into each other, then run 5v across these here two wires on one of the plugs" -- is that true or is there more to it **if I don't need the monitoring and control stuff** ?
thanks