Battery temperature and charging advice

jimbuck
jimbuck Registered Users Posts: 46 ✭✭
in Solar Beginners Corner #1
Hello, This is my first post here although I have been reading as much as I can for some time now. I have many screenshots of BB's calculations regarding bank sizing etc!
I am upgrading my battery bank to two Trojan T105's or a pair of crown 220's at 12volts. I decided to measure the temperature of the battery Compartment on this cold frosty morning. It was a minimum of 2degrees c and a max of 19.5c after having the heater on (blown air pipes pass through the battery area under the bed)I live in an off grid trailer with limited space so the bank can't be moved. Will this temperature have a big effect on the life span of the batteries? I know that the ambient air temp will not be the true battery temp as it takes time for this to change. I'm expecting the temp to be between 2-20 degrees between winter and summer.
As you can see below, I'm well under panelled right now so plan to supplement the batteries using a sterling 30amp charger. I will take the batteries to about 25% dod over 2 days with the solar supplementing in between and then will run the generator. Is this a satisfactory arrangement until I can get some more panels?

I'm About to buy a new sterling pro charge ultra 30a charger to run from a Honda eu10i generator.

Many thanks for any help,
Jim



Victron MPPT 12/30 cc with Bluetooth
Victron BMV battery monitor
Victron 300w pure sinewave inverter
2x 100w mono panels.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    The temperatures stated are not radically high or low, the actual battery temperature will take time to change, a remote temperature sensor insulated from ambient temperature, under styrofoam for example, would take care of charging voltages, with the controller, most auxillary chargers won't have this ability, but better than nothing to get something in before your solar takes over to finnish the job. It would seem you have done some research regarding array size etcetera, so won't comment further.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,109 ✭✭✭✭✭
    edited November 2017 #3
    Cold tempratures tend to slow down battery aging and self discharge. As long as your battery is in a relatively high state of charge cold temps will not hurt it.
     Here's a good read on the subject,   http://batteryuniversity.com/index.php/learn/article/charging_at_high_and_low_temperatures

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #4
    Personally, I would reconsider the choice of charger. If my arithmetic is right, charging voltage should be increased by ~ .75 volts at your low temp. Although the chemical reactions in the battery happen more slowly at lower temps, they still happen. Without temp compensated voltage, there's some risk of sulfation from long term chronic undercharging.

    This wouldn't normally be a problem, as off-grid we tend to typically use the generator just to bulk charge up to ~ 80-85 SOC, and finish with solar doing a temp compensated absorb. If your solar can finish charging, and the controller has a remote temp sensor to properly finish absorb, it isn't an issue. If you're relying pretty much entirely on the generator though, it could be.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • jimbuck
    jimbuck Registered Users Posts: 46 ✭✭
    #5
    Thank you for your replies.

    I have looked into the charger and it is the only one here (uk) that is customisable e.g. 14.8v absorb and can be run from a poor power source (generator) I cannot afford the Honda inverter genset yet but allready have a standard 2k generator. There is also a remote temp sensor. It mentions temp compensation but doesn't give specific values.
    Thank you for the link to more information, I will read that tonight.

    I feel confident that the batteries will not be affected at the temperature ranges stated so I will go ahead and order them, I just need to build a bigger box and vent it to the outside. I think the temp sensor mounts to a terminal but I may be wrong. I will try and line the box with some insulation too.

    Many thanks, Jim
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #6
    If it has temp compensation, you should be fine. My banks live in an unheated crawlspace. Ambient temps can go below -40°C, crawlspace can get to -15ish.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • jimbuck
    jimbuck Registered Users Posts: 46 ✭✭
    #7
    Thanks Estragon

    Jim
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