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Comment by John "T" Nordhoff on March 6, 2019 at 9:58am

Kevin, sorry Im here late but FWIW I will add my comments:

One advantage of AGM is less venting of hazardous gas and acidic fumes to worry with and not having to check and add electrolyte  HOWEVER they still require adequate ventilation as far as "heat" is concerned.

The answer to what combination of series or parallel or series parallel connections is concerned is YOU MUST ADD THE TOTAL AMP HOURS. IE if you had two 12 volt 100 Amp Hour batteries in parallel you end up with 200 AH at 12 volts. Same if you had two 6 volt 200 AH batteries in series you also end up with the same 200 AH at 12 volts. I just replaced four six volt Lead Acid Trojan T-105's  (225 AH) in series parallel for 450 amp hours with two Renogy 12 Volt AGM  208 AH in parallel for 416 AH. Since then I added yet another Renogy AGM. You might take a look at FullRiver and Lifeline and Renogy and Trojan for AGM's. I bought the Renogy 12 Volt 208 AH size 4D batteries for $247 delivered and loaded in my car from Walmart but they raised right after that, they were $399 on Renogys website  

When connecting solar panels in series or parallel if shading of some of the panels is an issue then parallel connection is best. In series voltage is additive and theres less current being carried down to the charge controller. Many MPPT charge controllers will take up to 100 or more volts input no problem and convert it to 13 to 14+ charging volts. 

John T  Retired Electrical Engineer

Comment by Russell E Johnson on March 4, 2019 at 7:02pm

I don't know enough about AGM batteries to answer that question. My guess is they can be used in un-ventilated areas, but would have to check that out.

Comment by Kevin F Smith on March 4, 2019 at 6:52pm

Thanks Russ!  Am I also correct in assuming that AGM batteries can be stored and used in unventilated compartments?

Kev

Comment by Russell E Johnson on March 4, 2019 at 6:05pm

Hey Kevin, yes, you are correct with your series parallel statement. Glad things are coming together for you.

Comment by Kevin F Smith on March 4, 2019 at 11:57am

(p.s.:  My charge controller will bring the 21 volts X 4 down to charge voltage, so I'm not worried about that number right now).

Kev

Comment by Kevin F Smith on March 4, 2019 at 11:56am

Just to refresh my memory:  With two coach batteries, in series, voltage doubles and amp hours stays the same...and in parallel, voltage stays the same and amp hours double, correct?

All four of my solar panels were delivered today with no shipping damage, and each panel is putting out 21 volts.  So now I have to design my storage battery system.  I only have room for 2 coach batteries in the stock location (under the steps in the doorway).  So, assuming my above statement is true, that using 12 volt batteries hooked up in parallel leaves the voltage at 12 volts, and doubles the amp hours, I'm thinking of going with Trojan AGM 12 volt batteries instead of Trojan wet cell 6 volt batteries.  That way my amp hours doubles, and I can expand the battery bank into either storage compartment on either side of the entry door with more Trojan AGM 12 volt batteries without having to worry about hydrogen gas and acid venting. 

Am I correct?

Thanks!

Kev