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Old 07-14-2015, 04:26 PM   #11
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thinking about solar?

As I explain here, the maximum watt hours in a 80 AH battery is 80 AH times 12 volts or 960 watts available for 1 hour.

It does not matter what you WANT to power, you can't get blood out of a stone.
Thank you again, just read what you wrote on that thread. Everything you wrote does make sense, basically, solar is useless for boondocking. I have seen panels on trailers and am sure they are not that big of panels! I wonder how they make out with them, especially those that mount them flat on the roof?

Maybe they are using them to just charge their cell phones and laptops?

Jim
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Old 07-14-2015, 04:28 PM   #12
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Typical Marine batteries are "Dual Purpose" so they "technically" did not lie to you. They are just crappy Starting Batteries and Crappy Storage Batteries at the same time.

Starting Batteries are designed to give up huge amounts of amps (hundreds) in a short period of time (measured in minutes). The plates are thin and "waffled" so there is a large surface area to launch electrons from. They recharge quickly because the large surface area has lots of holes for the electrons to find and "be happy."

The downside is they have very little staying power; not very much capacity beyond the surface.

True Storage Batteries (Deep Cycle or Solar) have THICK FLAT surface plates that have LOTS of holes for electrons to live but they are deep inside the lead. It takes a time (and power) to push the electrons (who are happy on the surface) out of their homes into holes deeper inside.

Once filled to capacity a storage battery holds many times the electrons than an equivalent sized starting battery.

The downside to a deep storage battery is it can't "give them up" as easily as the electrons deep inside can't get to the surface fast enough to provide high current.

For inverter use two 12 volt or 2 6 volt Deep Cycle batteries are optimum for a 1000 Watt inverter (what I have).

For a 2500 Watt Inverter 4 12 volt or 4 6 volt batteries are normally found.

I recommend these:

http://www.amazon.com/dp/B00DDYRRX8/...I1TCMLCD7DY0F6

With free shipping they will give you the most bang for the buck (310 AMP HOURS) in a Gel Battery. While many say 6 volts are better, I like 12 volt batteries due to the ability to lose one and still have 12 volt power and you can keep camping.

Lose a 6 volt battery and the trip is over.
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Old 07-14-2015, 04:32 PM   #13
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Thank you again, just read what you wrote on that thread. Everything you wrote does make sense, basically, solar is useless for boondocking. I have seen panels on trailers and am sure they are not that big of panels! I wonder how they make out with them, especially those that mount them flat on the roof?

Maybe they are using them to just charge their cell phones and laptops?

Jim
Most are "supplemental power"; any power from the sun is less from your battery stack. It can lower your generator fuel costs by running it less often.

Some of those panels are 245 Watts each. 3 of those and some common sense battery usage can eliminate the need for a generator BUT no air conditioning and limited microwave usage.
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Old 07-14-2015, 04:48 PM   #14
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Nobody mentioned about wire size . . .
Even for a small 2000 watt inverter, at 12 volts you need HUGE cables (P=E*I).
You'll be drawing 10 times the current compared to 120 volt.
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Old 07-14-2015, 04:52 PM   #15
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As an EE, I understand all of that, but still stand by my statement: Inverter size will be determined by what his maximum and continuous loads will be. The battery size will only determine how long he can pull that load before the battery will be depleted. There is no direct relationship.

Just checked on a couple (2000 - 3000 W ratings). (Per manufacturer). In in the OFF position with the remote control it will use ~300mah. In the ON position with no load, it could double that. I know mine (2000w) uses that much. I suspect some of that is input cap leakage, the other electronics involved and probably some other resistances used for noise reduction. In any case, a small amount of load.
Thanks for the update on the "off" draw.

You are right there is no "direct relationship" other than how long the battery will last before the inverter pulls the battery down below its cut out voltage.

I do feel the while you are correct, you might be giving the original poster (OP) a false sense of how much inverter would be cost effective based on his battery bank size.

Sure he could buy a 5,000 watt inverter, but since he could only use about 400 watts for an hour or two before his battery voltage dropped below cut out how does that help him?

The first time he plugged in a coffee pot and the inverter goes into alarm before the water is warm he might have words to say.

Watching an AC TV with a DVD player for the evening for a few hours is about all you will get out of a 1 battery system provided you don't need the heater much that night.
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Old 07-14-2015, 04:55 PM   #16
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Thank you again, just read what you wrote on that thread. Everything you wrote does make sense, basically, solar is useless for boondocking. I have seen panels on trailers and am sure they are not that big of panels! I wonder how they make out with them, especially those that mount them flat on the roof?

Maybe they are using them to just charge their cell phones and laptops?

Jim
Solar is great for boondocking; just not a small panel more useful for keeping a cell phone charged.
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Old 07-14-2015, 05:01 PM   #17
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Thanks for the update on the "off" draw.
.... I do feel the while you are correct, you might be giving the original poster (OP) a false sense of how much inverter would be cost effective based on his battery bank size.....


We agree. The OP would have to understand that.


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Old 07-14-2015, 05:10 PM   #18
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Nobody mentioned about wire size . . .
Even for a small 2000 watt inverter, at 12 volts you need HUGE cables (P=E*I).
You'll be drawing 10 times the current compared to 120 volt.
2 gauge should do it. As long as your run is no to long...
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Old 07-14-2015, 05:15 PM   #19
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While many say 6 volts are better, I like 12 volt batteries due to the ability to lose one and still have 12 volt power and you can keep camping.

Lose a 6 volt battery and the trip is over.
Two 12v or 4 6v will work the same. Lose a 6v battery and just change your wiring a little and keep going also. I do like the gel batteries but they are expensive.

Got to do some thinking and look at the bank account. I think solar is going to be out of the question. I do think I will be changing out the marine battery and add another 12v or two 6v ones. I have a 750 watt inverter I can play with for a while. Got to check, can't remember if it is a full sine wave or not. Also have the Honda 3000is generator. Going to have to be a little picky about where I go so I know I can run it.Was only going to take it when I figured I would need the AC but it would make a heck of a battery charger!

I HATE thinking, gives me a headache!!

Jim
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Old 07-14-2015, 05:32 PM   #20
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Two 12v or 4 6v will work the same.
Was thinking along the lines of 2 batteries. 2 six or 2 12.
The AH will be about the same.

Two 200 AH 6 volt batteries will give you 200 AH at 12 volts
Two 100 AH 12 volt Batteries will also give you 200 AH at 12 Volts.
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