[RE-wrenches] FLA battery setpoints with larger arrays

[frenergy]

This is good stuff, enlightening...but begs another small? detail that has obvious big ramifications.  Where o where does the BTS get placed to best read the actual "temperature of the battery"?  It's too big to fit on many terminals especially once cabled, it's certainly not very accurate when stuck to the outer case of a dual cased Surrette and probably only somewhat more accurate when stuck to an L-16 top.  Aren't we looking for electrolyte temps?  

        Many times the BTS doesn't survive its original location after a few years of battery acid.  Rather than "insulated" from the surface its been assigned to with 2-sided tape, it seems like it should be in direct contact with that surface with a dab of thermal grease between.  Or, couldn't a wrench be trusted to drill a 1/4" hole in the top of a representative cell and insert an acid proof sensor into the electrolyte with a formed snap-in plug (rubber, silicone, nylon??) behind it on the lead, to seal it where it enters the battery case?

        Just saying, if we really need (and I think we do) accurate battery temp for temp regulation and battery health, what we're using now is substandard.

Bill
Feather River Solar Electric
  ----- Original Message ----- 
  From: Ray Walters 
  To: RE-wrenches 
  Sent: Friday, May 22, 2015 3:33 PM
  Subject: Re: [RE-wrenches] FLA battery setpoints with larger arrays


  I thought I'd post some info on Battery Temp from a few manus:
  HUP Solar One: do not exceed 105 F
  Full River AGMs: max recommended operating temp 104F
  and from Trojan:  for every 10C increase in temperature the reaction rate doubles.  Thus, a month of operation at 35C is equivalent to 2 months at 25C.  Heat is the enemy of ALL lead acid batteries.  Even small increases in temperature will have a major influence on battery life.
  Their T105 RE battery has a max operating temperature of 113 F

  I think more batteries are hitting high temperatures than we may realize.  This info from Trojan that a battery at 95F (35C) will only last half its rated life (at 25C) is very concerning.
  Once again, thanks Bob and Midnite for giving us a tool to combat over temperature of batteries.  We always knew cold was a problem, now I'm realizing heat could be just as important.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer, 
Licensed Master Electrician
Solar Design Engineer
303 505-8760On 5/22/2015 3:24 PM, boB at midnitesolar.com wrote:

    I'm very glad to hear Midnite added the high temp disconnect to their system.  They may have saved a life.

      Bob, is battery temp logged, so we could see how often a system quits charging for high temp, and just what the battery temps are running?


    No, but that is on the list as are other things to data log.

    Hopefully the temperature is adjusted higher than it would ever get to under normal circumstances.

    I could see some future systems wanting to be able to regulate Absorb on battery temperature mixed with other
    parameters some day.   Could get REALLY complicated if you wanted to.  We're learning more and more
    about what is good for batteries.

    boB







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