long vacation question.

jzeier
jzeier Registered Users Posts: 1
Use solar off grid system 6 winter months then gone in summer. Conflicts thoughts on line - detach water batteries and they will go dead, some say permanently. Leave them attached and water boils possibly causing fire or killing batteries. 8 large batteries so I can't move them. I turned inverter off but don't know of a charging switch to turn off (recent purchase and seller only showed me the off switch for inverter said they didn't know of anything else. There is no significant load on the system when gone. ???

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    Welcome to the forum Jzeier,

    If these are flooded cell lead acid batteries--You don't want to leave them sitting without charging. More or less, at ~75F and above, they will self discharge to 75% state of charge in 30 days--And if not recharged, the batteries will begin to sulfate (technically sulfate even faster) and when you comeback in 6 months, the batteries will have lost most of their storage capacity/be close to dead. If batteries are over 75F, they will even self discharge faster (for every 10C/18F increase in temperature, they will self discharge 2x faster--i.e., at 93F will need charging every 2 weeks). Conversely, every 10C decrease in temperature, self discharge is cut by 1/2 (and batteries age at 1/2 the rate).

    Normally--Suggest turning off any and all loads (some people have security systems, and we need to take those loads into account). And have the solar charger set to "float" the battery bank (typically around 13.6-13.8 volts) while you are gone. There should be little (if any) water usage by the batteries.

    Also, if you have other issues (such as possible solar panel theft in your area)--you can typically get away with a much smaller solar array--Typically 1-2% rate of charge (or almost 1/10th the size of your normal array). Take down the full array and leave/install a small array and a small solar charger to float the bank.

    More or less--It all comes down to your solar charge controller--As long as you know it will float the battery bank while you are away--You are golden.

    If the charger will charge >14.x volts (for a 12 volt system), then you want to change/reprogram the solar charging for summer storage--Or install a second/smaller charge controller that will properly float your batteries while you are away.

    And you may want to closely monitor your solar system while you are there... On a day where you do not use solar, what does the charge voltage settle out too?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,101 ✭✭✭✭✭
    I maintain neighbor's batteries in the summer. I shut down all loads and set Bulk/Absorb voltage setting to 13.6, 27.2 or 54.8 volts which is basicily, float voltage. The batteries stay fully charged but use very little water.

    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.