Originally Posted by n1joh
hi all i hve a solar system on my coach 2009 georgetown 373 ds. i have two 110 panels on the roof and a gp-25 regulator with 4 trojan t-105 plus batteres(I think) I install a 3000 watt inverter with the remote. i will be at the rally on Aug 11 Sat. feel free to stop by. i am new to solar too and still learning. I have tested it and i can run the air when i go shoping at wally world to keep the watch dog cool.
Those 4 batteries (a double bank of 2 x 6volts) have an amp hour rating of 450 amp hours capacity (225 each) http://www.trojanbattery.com/Products/T-1056V.aspx
. The graph below is for a 100AH battery.
Not sure what the amp draw on compressor start up is for your air conditioner, but say it is 15 amps and it is the only draw on your entire system. That is 1800 watts. This is well under the 3000 watts (most likely 3500 peak) your inverter is capable of producing.
1800 watts at an average voltage of 11.5 volts means you are taking 160 amps out of your battery bank (buffed with 15 amps solar support [2x110 watt panels = 220 watts/12 volts = 15 amps] or 145 amps tasked to the batteries).
With 4 batteries providing that 145 amps each bank is tasked to provide 1/2 of the electrons or 72 amps per hour out of the 225 available to the bank.
Since the graph is based on 100AH batteries we will need to "normalize" for the graph. (72/225)=(X/100) solve for X = 32 amps out of a 100 AH battery.
Plotted that on the graph says those batteries will reduce the effective capacity of your banks 50% to 225 AH for the 4 battery system fully charged.
Delivering 145 amps out of a 245AH bank will deplete your batteries from fully charged to 10.5 volts inverter cutout in 1 hour and 40 minutes (or so).
Obviously this assumes the compressor runs the entire time (which it does not).
That is how I understand how the calculations work.
How does that match up with your experience?
Oh, and I am totally jealous of your battery bank. I have two 70AH Deka DC-24s (140AH when they were new) pushing a 2400 Watt inverter.
My AC would most likely run about 30 minutes before my batteries died.
When I had only 1 battery my coffee maker would kill my battery by the time the coffee was done.