norman launier wrote:will a 100amp controlier handle 4 12volt -100amp batterys connected in a parell do damage to batterys or inverter t-y

It's not so much the controller itself as the number of amps passing through it. As David alludes to above, too few, or too many amps is problematic. Here are general rules of thumb for different battery chemistries, where "C" is capacity in Amphours (Ah), measured over a 20 hour period. Battery makers will call this the "20 hour rate". That means the TOTAL number of Amphours you get draining the battery slowly over a 20 hour time period.

Flooded lead-acid : charge at 1/20th of C minimum, 1/10C good, 1/8th of C max

AGM: charge at 1/20th of C minimum, 1/8C good, 1/5th of C max

LiFeP: no real minimum rate, 1/10C OK, 1/4th of C max

What is the size of your batteries, 100Ah?

Should be pasted right on the label if it is an off-grid battery. If instead of Ah it is instead listed as "cranking amps", then you have selected the WRONG kind of battery for

solar. Let's do the math for a 100Ah battery. Remember that in series volts add, while amps stays the same. In parallel, amps add while volts stay the same.

If you take two 100Ah batteries and wire them in series, you get 100Ah of capacity at 24V. If you take the second two 100Ah batteries and wire that pair in series, you also have 100Ah at 24V. When you parallel the two 100Ah strings, you get a total of 200Ah at 24V.

The final bit of math you need to digest is how many amps you need to properly

feed that battery bank without overdoing it. Let's say you have 100Ah flooded lead-acid batteries. The math is....

(200Ah/

X 25Vcharging X 1.175fudgefactor = 25 X 25 X 1.175 = 734W max.

Now, it you wanted to charge at an OK rate instead of a maximal rate, the math would be....

(200Ah/10) X 25Vcharging X 1.175fudgefactor = 20 X 25 X 1.175 = 588W.

If you try to squeek by with just bare minimum (NOT recommended) the math would be....

(200Ah/20) X 25Vcharging X 1.175fudgefactor = 10 X 25 X 1.175 = 294W.

The math will of course change as the type of battery changes. Just plug in the Ah value of your battery with the capacity fraction for your battery chemistry, and you can figure it out yourself.

When you are ready to hook up everything, just tell us what controller you have, and what solar panels you got, and we can help you with the most optimal wiring scheme. If your controller is MPPT, you need to keep your solar strings at least 40V, and the maximal Voc less than the limit of your controller.