Battery types & distribution, over time [RE-wrenches]

[Allan Sindelar]

----- Original Message -----
From: <jberdner at sma-america.com>
 This means more watering and more energy lost to
> self discharge.  The also require periodic equalization to get the best
> performance.  IMHO, you want to charge them harder than most people
> think.
> Run the bulk set point way up there and then back it off when the
> watering becomes excessive.

A piece I'd like to add to the watering issue:
My own home system has a 1kW array, 24V with 12 Trojan T105s: very mundane
stuff. The array is pretty hot relative to battery size, around a C/20
charge rate sometimes. We use an SB50 Solar Boost. I have the bulk setpoint
pretty high, around 30V, and it runs to 31.2 or so in winter. Most sunny
days we charge full year-round.
I add water twice a year, and I never have exposed plates from having waited
too long. I think that one of the unheralded benefits of the Solar Boost is
that it uses the net charge rate needed to maintain bulk setpoint in order
to determine acceptance (absorption) duration before dropping into float.
That is, if the batteries are in good shape and able to absorb finish
current, there is no time-determinate absorption cycle. So I gas every
cycle, but not to an excess that necessitates frequent watering. We also the
remote shunt feature, so the absorption cycle remains more or less
independent of the system loads, too. It's a pretty nice unit.
Allan at +E

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