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Old 07-27-2015, 07:38 PM   #31
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Quick question. Does a 2000 W inverter draw the full 2000 watts or only what is needed o run what is running off the inverter?
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Old 07-27-2015, 08:05 PM   #32
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Quick question. Does a 2000 W inverter draw the full 2000 watts or only what is needed o run what is running off the inverter?
Only what you plug in up to the 2000 watt rating; BUT

and its a big one; you are dependant on the battery(s) to supply the amperage to "make" the wattage. Once you start pulling serious amps, the capacity to supply amps drops rapidly. This will pull down the voltage and put the inverter into alarm and it will shut down.

Suppose you have a 2000 watt inverter and you run a 1500 watt microwave; you also have a single 12 volt 100 AH battery (will supply 5 amps for 20 hours = 100AH).

1500 watts of AC requires (about) 1500 watts of DC through the inverter or 1500 watts divided by a nominal 12 volts or 125 amps.

The problem is something called the Peukert Effect which is a characteristic of deep cycle batteries that makes it "hard" to get amps out of the thick storage plates. This will reduce the "real capacity" to a tiny fraction of the 5 amp load capacity (see chart - OFF THE CHARTS! - extrapolated to about 15AH).

You can run that 1500 watt microwave (or coffeemaker) for about 7 minutes before it kills a fully charged 100 AH battery and the inverter alarms.

So how do you fix that? Add batteries. That way the 125 amps is "shared" across multiple batteries and no single one sees that much demand.

4 - 100AH 12 volt batteries (Each "sees" 31 amps) so each batteries capacity is only reduced to 55AH (BANK Capacity 220AH or you can run the microwave at 1500 watts for 220/125 or about 105 minutes).

My 2 battery 150AH system can only "feed" a 400 watt inverter and still have enough juice to use other DC items in the camper. (I DO have a 1000 watt inverter BUT I never use much more than 300 watts of its capability when boondocking (Watch TV for a few hours, lights, water pump, maybe some nighttime heat). I still need to recharge my batteries the next day.

Inverter size above the capability of the battery stack is wasted money better spent on a better (smaller) inverter and another battery.

Hope that helps.
Herk
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Old 07-27-2015, 09:25 PM   #33
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Thank you Herk.. I am only interested in running the refrigerator, which is AC/Propane, while I am on the road. I don't feel safe using propane on the road. When the inverter is in use, it will be plugged in to the tow vehicle, charging the battery (I hope). I know I overbought but I wanted the wife to have the option to use her hairdryer if we stop overnight boondocking. Again, it would be plugged into a running truck. Appreciate the insight.
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Old 07-27-2015, 09:42 PM   #34
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Thank you Herk.. I am only interested in running the refrigerator, which is AC/Propane, while I am on the road. I don't feel safe using propane on the road. When the inverter is in use, it will be plugged in to the tow vehicle, charging the battery (I hope). I know I overbought but I wanted the wife to have the option to use her hairdryer if we stop overnight boondocking. Again, it would be plugged into a running truck. Appreciate the insight.
If I may ask, how do you plan on running the fridge on the inverter while driving? This is not as straight forward as you might think...

As to the hairdryer, you may have similar issues as the amperage needed is much higher than the TV can deliver through the umbilical.

Here is a great article on why alternators make horrible deep discharge battery chargers.
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Old 07-27-2015, 11:03 PM   #35
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I installed an automatic transfer switch that will switch power to refrig. receptical when not plugged in to shore power.
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Old 07-29-2015, 10:17 AM   #36
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I finally heard from Forest River customer service dept about the battery requirements for the 29RE. As I suspected after reading multiple threads on this topic, my trailer is designed for three 12 volt batteries, but FR said that 2 will work...."as long as"...they are wired in parallel. The dealer had wired them separately, and since the inverter does not have a charger built in, that battery would not hold up, plus, when the high current demand of the level up and slides were placed on the system, a single battery simply could not meet that demand.
Anyway, I'm debating whether to buy another battery or see how the system works with just two. The thing is, when the slides AND the level up systems are used within a couple of minutes, that's a huge current demand. But, if I plug the shorepower up beforehand, that will at least add the converters current capacity to the mix.
I could also keep the trailer's umbilical to the truck plugged in as well, although that's minimal recharging.
It would be nice to just have two batteries to maintain, but I don't want to deal with possible voltage drops and the resulting high current induced heat to the hydraulic systems motor.
So.....go with two batteries and a modified set up routine, or buy another battery at $90 and have a third battery to maintain plus another 50 lbs to haul.

Opinions? thoughts? suggestions?
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Old 07-29-2015, 04:14 PM   #37
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I would get your two batteries wired up properly in parallel and fully charged. Then, disconnect from shore power and operate your slides and level up like you would at a camp site. Check the batteries and see how they held up. If they handle it OK, all is good. If not, spend the money on another batteries and some cables.
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