Stand By Batteries and Charging

SouthAfrica75SouthAfrica75 Solar Expert Posts: 36
I have a small system consiting of a 1,200 watt inverter connected to 2 x 100amp deep cycle flooded batteries that would be put to use if we were to loose power after a hurricane.

It's been 2 years on stand-by and luckily have not had to use it.

This year when we thought Ike was possibly headed to South Florida I did top-off charge both batteries to be ready just incase. They both took about 4 hours to reach full charge after a year of sitting.

Here is my question:

With these batteries not being used and just sitting and charged only if I may need them, should I at least draw power on them once in a while and recharge or is it better to just let them sit and if I may need them do a charge up as I did for Ike ?

Also how long would these batteries last just sitting, not being used

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Stand By Batteries and Charging

    unless i'm reading this wrongly, i'm afraid that sulphation has taken root in your batteries as they can't be left sitting idle for long of periods of time due to the fact that they drop some of their power over time just sitting. some lead acids can lose as much as 7% each month while some quality agms will lose as little as 1%. they should have a small float charge to keep the batteries from losing their power and allowing sulphation to start. this sulphation will shorten the lifespan of your batteries and the ah capacity as well. i hope it's not as bad as i think it to be, but you did damge them some without a doubt unless your meaning of stanby is with a float charge to them.
  • BrockBrock Solar Expert Posts: 639 ✭✭✭✭
    Re: Stand By Batteries and Charging

    Niel is right on as usual. A friend of mine has my old DR2412 and 2 Trojan T105's. I had him disconnect and reconnect the power every two weeks. This forces the inverter to go in to a bulk / absorb / float cycle. He got tired of doing that and so I suggested a Deltran 1.25 amp charger. Once his batteries were full it is more than enough to keep them topped off. The Deltran charger will actually go back in to absorb once a week to make sure the batteries are topped off.

    Bottom line if you let them sit with'out' a trickle charge on them they will be damaged, basically the sulfur sticks to the plates and won't come back off. If they are kept charged this won’t happen and the batteries will be ready to go.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • SouthAfrica75SouthAfrica75 Solar Expert Posts: 36
    Re: Stand By Batteries and Charging

    Well this totaly blows the big one........

    Guess it's too late to put them on a small solar trickle charger
  • BrockBrock Solar Expert Posts: 639 ✭✭✭✭
    Re: Stand By Batteries and Charging

    We have no idea how damaged the batteries might be, maybe just a little, maybe a lot. But putting a solar charger on them will at least prevent it from getting worse. Assuming the solar has some sort of charge control and doesn't over charge the batteries.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Stand By Batteries and Charging

    i agree with brock as we really don't know the extent the damage may have occured. put the trickle charger on it in the future anyway, but right now do a charge cycle on it. charge it fully or make sure it is and then drain it down to half of its rated ah with a fixed load over some time. let it rest for 3 hours and record the voltage, the load current drain rate, and the time transpired to reach that half way point for us and then give it a full charge again. tell us what the battery make and model is too.
    you state they are each 100ah for a total of 200ah. the halfway point would be 100ah drained and a load of 10a for 10hrs or 20a for 5hrs would take it to that point. know that a proper test is to drain it down 100% or 100% dod and that is to get it to the at rest voltage of 10.5v. lower than 10.5v read indicates a loss of capacity. i don't like doing it that way as that could do further damage.
Sign In or Register to comment.