OK guys, here is a question for all you battery nuts.
I have an old car battery that I keep charged through a small 5W solar panel and charge controller that I use from time to time for emergency power. I know that car batteries won't hold up to this kind of use, but it was taken out of my Honda that was the victim of a metal guard rail jumping in front of it (I swear) so it was free.
Now I have my old Ford van that will be scrapped very soon(no guard rail accident, just age).
I would like to keep the battery from it and keep it charged just like the other one.
My question is...
Can these batteries be wired together and charged at the same time even though they are different sizes and CCA?
yes, you can do them in Parallel, the more power will go to the weaker one. As told to me by a mechanic this week.
Now you do need a stronger solar cell though, 25-75 would be better.
Thanks WildE,
Ya I know, a stronger panel in getting higher on my "to buy" list!
Canadian Tire and Princess Auto have sales on these next two weeks.
I think I read somewhere that the total power withdraw will never exceed that of the smallest battery in the bank. Someone please correct me if I am wrong.
Most solar cells are in the 27 volt range. If you have a 12 /24 volt automatic charge controller you would have the option of connecting them in parallel or series. A failed cell in a parallel bank will sap energy as the other cells try to charge it. This occurs continuously which adds up in sapping energy. This can cause heat and loss of water in the failed cell that can run a battery down by itself.
I would charge each battery separately to see if it will reach its maximum voltage. The easy way to tell this is after a day or two of charging the charging light will go out and the charged light will come on the charge controller. If either battery will not take a full charge do not connect them in parallel. Charge them at 24 volt in series or charge them separately.
If you had a large load on the batteries when you were using them it would be ok to connect them in parallel to get a greater capacity. Otherwise it would not be a good idea for continuous charging unless both batteries are good.
Does anyone have any experience with Crown deep cycle batteries for solar?
I'm looking at a Crown 12v 105 ah unit for about $130.00.
This is not for a large setup, but simply to provide some backup led lighting and other low draw items such as NiMh charging.
The panel would ideally be a 40w and a 7amp charge controller.
Gravlore - old post, but you are right, max power will be what the weakest battery can provide. Doesn't have to be a smaller battery though, it can be 2 equally sized batteries but one has a bad cell or some other fault that reduces its capacity.
Denob - I have crown batteries in my system. 8 6v 395ah batteries wired in series for a 48v system. Only set I've ever had, they're about 2.5 years old and holding up well. I don't really understand power, so I can't comment on that proposed system, but I have learned some battery stuff.
-keep the water full - the plates must always be submerged. always use distilled water
-don't draw them down too far - my 48v system shuts down if the batteries get down to 40v
-never leave the batteries drawn down for any length of time
-=bs=-