[RE-wrenches] Battery Life (Air conditioning for batteries in high temperature climate)

[Starlight Solar, Larry Crutcher]

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 at 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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