Battery Watering Question

Coach Dad
Coach Dad Solar Expert Posts: 154 ✭✭

The Trojan Battery Manual states: “In cold climates with unheated rooms, water should only be added when the battery temperature is 45F (7C), of above.

What do you guys in cold climates do when your batteries are below 45F for 4-5 months out of the year?


  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
    edited July 2019 #2
    My suggestion (from sunny/not freezing California), look at the space between the top of the plates and the "fill line" (bottom of the split tube or whatever your battery uses) and only fill 50% to 75% of space... Do not fill to 100% unless batteries are warm and bubbling.

    Elsewise, the electrolyte level will rise and spill out the top of the battery bank.


    PS: You never want the plates exposed to air--They need to be always covered with electrolyte.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    If adding (small amounts of) water in winter, I would add when batteries are fully charged, then run a bit of an EQ to get the water well mixed in.  Like Bill said, not too much so they don't overflow when they warm up.

    My guess is they say not to add in case the water added sits at the top for a while before the next charge cycle and risks freeze damage.  If adding a lot of water, there could also be a risk of thermal shock to the cold plates.
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
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  • Coach Dad
    Coach Dad Solar Expert Posts: 154 ✭✭

    I wanted to update this thread in case someone else has this question. I sent an email to Trojan asking this question. 

     Answer: If you add water to your batteries and temperature is below 45-F, you should put batteries on equalization charge and stir the electrolyte for 3-4 hours.