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Old 08-01-2012, 08:22 AM   #11
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You are missing the point made in the graphs about amp draw and battery capacity. The more amps you try to draw from a deep cycle battery; the LESS capacity they have.

While 30 amps at 120 volts = 3600 watts, 3600 watts (plus inverter loss at that high wattage requires 4000 watts of DC input.

4000 watts of DC divided by 11.5 volts (average battery voltage 12.5 Full - 10.5 dead) is 350 amps demand from your battery system.

While not impossible, it would take a battery bank of 14 batteries (that weighs several thousand pounds) to deliver that wattage at that amp draw and keep the individual battery amp load to less than 25 amps (see the capacity vs amp draw charts).

There is not enough roof area to supplement that with solar. Most likely all available roof would be required to replace ONE of those batteries.

Like I said, I am NO expert. There are experts on the Solar forums and I highly recommend if you plan on an installation that large that you contact an expert.
Herk, I appreciate it, by the way, clearly I am no expert, but there is something wrong with your numbers, how can (in the example) running a the devices (in the example) for the hours (of fractions of hour) shown, could it possibly require 14 batteries. The total depleted is 126AH. I was trying to figure how many batteries would be required so not to deplete 50% (no more)... and further how many watts of panel(s) to be able to bring the batteries to float during a single day. With fourteen group 27 batteries at 50% the available AH is 630! or five times the amount in the example. Do you see what I mean? Based on your numbers I would need a 60KW generator to run an 120V alarm clock and a TV (joke!).
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Old 08-01-2012, 08:28 AM   #12
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Herk, I appreciate it, by the way, clearly I am no expert, but there is something wrong with your numbers, how can (in the example) running a the devices (in the example) for the hours (of fractions of hour) shown, could it possibly require 14 batteries. The total depleted is 126AH. I was trying to figure how many batteries would be required so not to deplete 50% (no more)... and further how many watts of panel(s) to be able to bring the batteries to float during a single day. With fourteen group 27 batteries at 50% the available AH is 630! or five times the amount in the example. Do you see what I mean? Based on your numbers I would need a 60KW generator to run an 120V alarm clock and a TV (joke!).
<sigh> I can see I am going no where with this.
Since you clearly are not getting the impact of the discharge graphs I am attaching a document on the Peukert Effect of discharge and battery capacity.

If after reading it (I did attach it previously) you still think it is possible to feed and water a 4000 (or even 3000) watt inverter in an RV, I can only wish you a great amount of luck in your endeavor.
Attached Files
File Type: pdf What is the Peukert Effect.pdf (164.4 KB, 33 views)
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Old 08-01-2012, 09:23 PM   #13
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solar system

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.
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Old 08-01-2012, 09:28 PM   #14
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Both my OEM digital TVs are 120VAC.
Wow! I installed a small flatscreen in the bedroom that I got from Wally World, and that is 120v, but my factory flatscreen has a 120v plug and adapter brick (that I store in a cabinet) but it plugs into a 12v power source.
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Old 08-01-2012, 10:03 PM   #15
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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.
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Old 08-02-2012, 04:03 PM   #16
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you are correct. it will run for about 1 and 1/2 hour. my inverter is a go power sw3000 which is 3000 watts with 6000 surge. i am thinking of adding more batteries.but because of cost have to wait. Are you going to the rally (Lou)
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Old 08-02-2012, 04:51 PM   #17
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you are correct. it will run for about 1 and 1/2 hour. my inverter is a go power sw3000 which is 3000 watts with 6000 surge. i am thinking of adding more batteries.but because of cost have to wait. Are you going to the rally (Lou)
Not this year.

DW health problems and house maintenance expenses have really put a crimp in our travels this year. I have only one 10 day camping trip scheduled end of September (to add 3 more state stickers) and we are done for the year.

I hope the DW will be back on her feet (literally) by the first of the year so we can head to Phillies Spring Training next year.
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Old 08-02-2012, 04:54 PM   #18
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you are correct. it will run for about 1 and 1/2 hour. my inverter is a go power sw3000 which is 3000 watts with 6000 surge. i am thinking of adding more batteries.but because of cost have to wait. Are you going to the rally (Lou)
This makes total sense since the AC is not the only draw on the batterys and the compressor/fan does not run continuously. Also your batteries may not be at 100% capacity at the start of your shopping trip.
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