Hi Larry,
I will bump up the absorb voltage to 29.6 V. How
long do you think the bank should stay in absorb
at that rate? The bank now seems healthy, with
the bad battery replaced. It does accept charge,
without going high prematurely. The max charge
rate from the array is around C/10. The system
can also be fast charged from a Honda 6500
inverter generator through the Outback 3524 VFX.
We have a Trimetric meter on the system. The
discrepancy between the percent charge and the
voltage is what demonstrated that we had a problem.
Thanks,
Drake
At 09:30 PM 7/19/2013, you wrote:
Hi Drake,
It always concerns me when I hear that a battery
bank reaches absorb setting very quickly. It
typically means one of two things: very few AH
were removed from the bank; the battery bank has
sulfated cells due to chronic undercharging. Far
too often I find the latter to be true.
Healthy batteries will accept current and hold
the charge voltage down with a fairly linear,
slow climb to absorption voltage. Sulfated
batteries do not accept current well which
allows voltage to climb rapidly as the battery
presents little load on the charging system. I'm
not sure how this plays into your original post
about a bad cell but it seemed worth mentioning.
My opinion is to aggressively charge, by using
higher voltage, large flooded batteries. This is
especially true when the PV system is moderate
or undersized. 29.6 volts is what Trojan
recommends. You can go as high as 32 volts on
the L-16's but make sure the temperature
compensation is installed properly and working. You will use more water.
One last comment, I highly recommend that ALL
off grid systems have a battery capacity monitor
installed. It's kind of like flying an airplane
without a fuel gaugeĀ
it might not end in disaster.
Larry Crutcher
Starlight Solar Power Systems
On Jul 18, 2013, at 1:11 PM, Drake
<drake.chamber...@redwoodalliance.org> wrote:
Tom,
The batteries usually reach absorb voltage
shortly after the sun hits the array. The reason
the bank wasn't working correctly is that one
cell was dead in one of the batteries.
I could increase the absorb time to 4.6 hours
and the voltage to 29.6, especially since the
bank has a new battery. That is longer and
higher than I'd previously heard recommended.
What would be the effect on water
consumption? How did you calculate the absorb time?
Thanks,
Drake
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