Roy,
Your post is most puzzling. As temperatures rise above 25C, battery capacity
rises and cycle life is shortened. The opposite is true as temperatures drop
below 25C. What do you mean by he was loosing "capacity" during summer months?
My question is whether anyone has run air conditioning on a battery bank to
increase the cycle life, not capacity, in hot climates.
As of my last conversation with the customer, he is willing to insulate the
small battery room and put in a portable A/C unit. I measured one unit that
only drew 620 watts while cooling. I expect that with sufficient insulation,
the A/C will only run a few hours per day. The home is vacant for 3-4 weeks
then used for 3-5 days. The DoD is only 5% while vacant. The PV charging system
is oversized now and should keep up with the extra load. I'll post again in
about 3 to 4 years to let you know if this plan works!
Thanks for everyone's input.
Larry
----- Original Message -----
From: Roy Butler
To: re-wrenches@lists.re-wrenches.org
Sent: Friday, April 22, 2011 10:09 AM
Subject: Re: [RE-wrenches] Air conditioning for batteries in high temperature
climate
Bob is correct, I do have an off grid client that uses an AC unit to keep the
batteries cool.
Although we're not in a high temp climate, it does get into the 80's and low
90's here
in the summer.
By my calculations, he was losing an 'average' of 10% storage capacity during
the 5 month
period from late spring to early fall. In July and August it was closer to
18%, but for calculation
purposes, 10% is close enough. His bank capacity is 4800AH @ 48 VDC. That's
230,400 watt hours
and 10% of that rounds out to 23,000 watt hours lost to heat.
I showed up one day to check something in the power shed and was dismayed to
see a window
AC unit installed there. An interesting customer discussion ensued and I had
to admit he was
correct in his calculations.
The Energy Star rated AC unit consumes no more than 3,000 watt hours per day,
even in the
highest heat. Essentially, he's 'spending" 3 kilowatt hours to 'buy back' 20
kilowatt hours of
storage. He got me on that one!
That reasoning didn't work on the 6 other AC units that appeared on his house
the following
week. But that's another story altogether!
Roy Butler
NABCEP Certified Solar PV Installer®
NYSERDA eligible PV & wind installer
PA Sunshine Program Approved PV Installer
Four Winds Renewable Energy, LLC
8902 Route 46
Arkport, NY 14807
607-324-9747
Hello Battery Wrenches,
Over the years I have had several battery banks in Baja and Sonora Mexico
fail in just 36 to 48 months. These have been L16 or 8D AGM or flooded banks,
24 and 48 volt systems. The charging systems are working properly and
programmed to manufacturer recommended set points and discharges are rarely
over 30% DoD. Some batteries are only used on weekends, some are discharged
daily. I believe what is affecting the short life is the high temperature they
live in for 5 months each year. Temps. can hit 115 F in vented battery rooms. I
have been thinking about a small air conditioner and insulated battery box to
keep the battery at no more than 80 F. There are some portable units that draw
about 600 watts and the run time would be very little with a highly insulated
enclosure. There is ample power to do this on the home I am changing batteries
in now. Has anyone done this and gained longer battery life?
Best Regards,
Larry Crutcher
Starlight Solar Power Systems
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