[RE-wrenches] concord batteries, EQUALIZE Them!

[R Ray Walters]

Yes, I've had a 48 v system survive a dead cell (Outback inverter), but 24 or 12 v systems are done.
So I guess the Sunnyboy can go down to 42 V?

R. Walters
ray at solarray.com
Solar Engineer




On Dec 1, 2009, at 3:41 PM, Richard L Ratico wrote:

> 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 ---
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