I believe the Sunny Island 5048 can be configured to remain "online" with up to
three cell failures. (Page 90, Sunny Island Manual). Of course, it is a 48 volt
inverter.

Dick Ratico
Solarwind Electric

--- You wrote:
I used to think that one string was optimal; until I had a single cell failure
take out an entire system for weeks. (try operating a 24 v system at 22v! )
I now think that 2 parallel strings is optimum,  3 is OK, and 4 is max.
At 4 parallel strings, we start spending more time looking to make sure all
connectors are the same exact length etc. to insure equal operation.
But of course how do you account for varying internal resistance of the
batteries......??
I've done 4 parallel strings at 144 DC of sealed batteries on an electric
vehicle, but we were very careful with our resistances, I even switched to
smaller wire, on closer strings, and calculated out the exact resistance, so all
strings were theoretically equal. This set actually just died, but achieved its
manufacturer's predicted cycle life. (B&B battery, 350 cycles to 80% DOD)
So if you're careful, 4 strings can work well.
Worst I've seen was 20 golf carts paralleled in a 12 v system, (10 strings) and
they didn't pull the main connections from across the set, just connected to one
end.
The results were very predictable, with the furthest batteries being chronically
under charged, and the closest ones being over cycled to a premature death.

Ray Walters
--- end of quote ---

