AGM battery

[janncoo]

I am trying to put my solar power together and need some info on my thinking to the batteries needed. I am installing 2 -68 watt flexible solar panels to the van roof and need to know if I am correct in thinking I need 2-12 volt agm batteries. The batteries will be inside my van.

 

[akrvbob]

Yes, technically that is correct you should use AGMs. With only 136 watts you might could use just one 12 volt but 2 is a much beter choice if you can afford it. AGMs are very expensive, at least $230 for true deep cycle batteries. You can use either 6 volt golf carts or 12 volt deep cycles if you are buying two of them.

I recommend 6 volt because you will know for sure they are deep cycle and not a hybrid like a marine. Unless you are buying a brand name, then you can trust they are true deep cycle. Golf cart AGMs will be about $250 each.
bob

 

[RVTravel]

Bob, if buying two and one battery dies early, do you have to replace both since batteries should be same age?

 

[akrvbob]

RVTravel, the easy answer is probably. Your batteries should be as close as possible to each other in size, condition and age. Within reason. If they are a year old and have been treated well then getting a matching battery should be okay.

If one battery is strong and the other one is weak, the strong battery will never be charged more than the weak battery which will lead to it's premature failure.
Bob