Batteries on ground

Chris11

I have a box under the solar array that I have all the electronics and bats inside...bats on the bottom separated from the electronics by a partition.  And yes, well ventilated.

I bought 4 new bats and so put the old 4 bats as a parallel storage source but underneath the box.  I meant to put insulation under the old bats on the ground but simply forgot before the winter.  So they've sat underneath the box on the ground but connected.  The temp sensor is attached to the new bats in the uninsulated box. Even though the bats in the box are unsulataed and the ones under the box are uninsulated I can't help but think there is a difference in temperature and that the difference in temperature is bad.

Am I correct and what can I do this spring so the cc allows for the difference in temps.

Thank you, Chris

BB.

Hi Chris,

I changed the title from Bats to Batteries--I was 1/2 way through your post before I was sure you were not talking about setting a bat box for real "bats". 

It probably depends on how deep you discharge the batteries... If they are shallow cycled (25% or less depth of discharge)--Then they are probably getting recharged roughly correctly and enough to not cause problems (such as excessive sulfation).

If these are deeply cycled daily--The cold batteries may not get fully charged every day--And they could sulfate faster (although daily cycling batteries do not quickly sulfate).

You can measure the voltage difference between the two strings and see how far apart they are:

• -0.005 volts per C per Cell * 6 cells (if 12 volt bank) * 5C difference (9F) = 0.15 volt "charging difference" between cold and hot bank

Most controllers/wiring are probably (at best) 0.05 to 0.10 volts "accurate"... So a 9F difference (as above) is not a serious charging difference problem.

If these are flooded cell lead acid batteries... Monitor water usage (cold bank using much less water than hot bank?), and specific gravity (should be no more than 0.015 to 0.030 SG units difference between cells--If all is OK).

-Bill

Chris11

Thanks Bill, 

I laughed at your thought that I was talking abouy real bats.

I don't use the system at all in the winter ... the batteries  just float all winter so I very seldom add water. .... luckily since it can be 894 degrees below zero sometimes and I would worry about freezing before the fresh water mixes with the electrolyte.