what is the best batteries to buy for 12v solar system?

Solar Power technology has come a long way in the last few years. You should update your system, or finance a new one: http://www.installeco.com/solar-power/

If sun is an issue, consider using wind power as an alternative: http://www.installeco.com/wind-power/

You may be able to combine the systems to generate electricity 24/7

If you don't get much sun on the panels then spending any money on this system is a waste of money . If you buy batteries then you want the best truck batteries you can get and they cost money . As they are old panels they have probably lost a lot of there effectiveness .

A better use of your limited funds might be to relocate the panels to where they will get a lot of sun.

As for the batteries, they need to be sized to your system. Try searching for "solar forum arizona", and asking one of the people there. They will likely ask you how many and what type of panels you have, and where you are located geographically.

I would try to get some ni-mh batteries as a first choice then Lithium. The ni-mh batteries are being replaced in a lot of uses with lithium even though the lithium are not tested for long term reliability. New lithium batteries are available for motorcycles but maybe if you shop around you might find used batteries for toyotas and other cars that use that type of batteries.

How cold does it get on your barn? Are trying fluorescent bulbs outside for a bit of first. They take time to 'heat up' if it's chilly outside. When you think they work ok, then it can be least expensive and easiest to move for them. In any other case, LEDs are the most efficient approach of doing it, however LED fittings are generally very highly-priced correct now. It will be years before they arrive down to a sensible price (recollect that they final about 5+ times as long as excellent fluorescent lights and 50 occasions so long as a typical bulb although!)

As someone pointed out it may have reduced effectiveness, so you may try to change its location to see if it gets more sun. You can try to get used batteries for your panels.

http://www.diysolarpanelscost.com/

You need deep cycle batteries. They are not the same as normal automotive batteries. Sometimes it is possible to buy them second hand from trawlers when they update, if you live near a port.

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