Yes. There's not even much difference to a single plate in a jar, if the surface of the plate is damaged in patches. Remember that lead acid plates are the same metal for both electrodes - it's just a transient surface coating (mostly lead peroxides) that makes them different. If you cause this coating to vary across a plate's surface, then all sorts of currents can flow.
However you obviously won't get this effect between plates in adjacent cells. This is just one reason why when lead acids fail, they kill a single cell quickly in favour of the others.
There's series resistance, which is low but not nothing, so the wiring wil take at least some of the heat, there's limited energy in the discharging battery, and thermal capacity in the overheated battery.
With a single cell failure there will be more heat dissipation to neighbouring cells than would occur with a whole battery.
I dont know the outcome, I've had batteries go ape but that was regulator failure.
I can't put the diodes at the meters - as the voltage drop across the diode would mean that the meters would not display anything - everything would go via the shunt. After all, the voltage across the meters will only be a few mv, even at full current.
Contactor with op-amp: - a possibility, however a contactor big enough will cost more that I'm willing to pay!
Schottky diode - I can get a 400A diode for about £50 - so not too bad. I'll fuse the output of the unit under this (using a 355A fork-lift fuse and holder) so it will never see over-current. Most high useage will be a few seconds at a time jumping a car, and the only continuous load will be from running the 3kw inverter - which draws upto
250A. As long as the diode is on a suitable heatsink we should be OK. I can live with the 0.6v voltage drop - you'd usually loose this over "average" jump leads anyway - and in my case I've over-engineerd the leads somewhat that the voltage drop would be minimal.
Changing zero point of existing ammeter - nice idea, but it would mean a home-made scale and bugger it up somewhat. If I can find a matching centre-zero ammeter from the supplier and get it to do this, I'll consider it.
I'll report back on what I end up doing and the results.
Quite so. Also check the voltage drop across the fuse, which will not necessarily be negligible. (And it could all be done with an op-amp and two 1N4148s in any case.)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.