Battery cooling answer (interesting)

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
After researching battery temps a little farther, I found some interesting data. Battery life is reduced 50% for every 15 degrees above 77. On the other hand at 22 degrees your capacity is cut by 50%, but your capacity will come back when they warm up. Things that make you go "HUH"
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
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    Re: Battery cooling answer (interesting)

    There are several links here somewhere to some very good battery info sites. (I can't remember where they are right off!)

    The trick is, battery LIFE decreases with temp, while CAPACITY decreases with temp. The difference is that the capacity comes back as the battery is warmed, the life does not as the battery is cooled. My batteries have lived in an extreme environment for 10+ years, in a unheated shed where the tmeps routinely get to -35, but never above + 20C. I got better than 10 years out of a set of t-105s, and I'm on the tenth year of a set of l-16's.

    I just built a new building and the batteries are housed inside, but away from any heat source.

    Icarus
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,440 admin
    #3
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    Re: Battery cooling answer (interesting)

    There is an engineering design "rule of thumb" (based on typical "activation energy" of materials) that works out to "for every 10 Centigrade (18F) increase in temperature life is cut by half. and for every 10 C decrease, life will double"...

    So, 20 C increase life is 1/2 * 1/2 = 1/4 life. We used this all the time for accelerated qualification testing of products (and to make sure we kept temperatures low in products to prolong life).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
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    Re: Battery cooling answer (interesting)
    icarus wrote: »
    I got better than 10 years out of a set of t-105s, and I'm on the tenth year of a set of l-16's.

    Icarus

    Icarus, good post on the T16s'. I'm interested in useable life of these batteries. Getting ten years under tough conditions like yours is good news.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
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  • System2
    System2 Posts: 6,290 admin
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    Re: Battery cooling answer (interesting)
    Mangas wrote: »
    Icarus, good post on the L-16s'. I'm interested in usable life of these batteries. Getting ten years under tough conditions like yours is good news.

    Tough conditions for humans, but great for the batteries, as long as they're looked after properly and not allowed to discharge too far ;)
    Way to go Icarus! I've had my L-16's about 6 years now and so far they seem the same as when new. Very pleased with them :cool:
    Between me and the MX-60 we must be doing something right now, in spite of the abuse I ignorantly put them through in their early, pre MX-60 years :cool:
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Battery cooling answer (interesting)

    I too have learned much over the years, especially from this site. I think that I under charged for many years due to no temp compensation. On the other hand , I never have discharged them below 80%. I draw down about 5-8% per day, and if I don't get fully charged for three days, I will bring them up with the genny. I rarely go three days with out running the generator for power tools, so the charge is essentially free. The batteries are in a styrofoam box so that they keep some of their heat from charging and discharging. The never get above 20C even in the height of summer, since they are insulated and have so much mass. Originally I was worried about freezing, but by insulating the box, and keeping them in a shed there has never been any danger, even with outside temps of -40c.

    It will be curious to see how the new set last inside the building. The old set is still being used in another location. We'll see if I can get 15 years. I have lost 2 of the l-16's, one after nine years, the second after ten. The string is now down to 4.

    Icarus
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