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Old 05-20-2016, 08:04 PM   #1
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Connect 1500W inverter to 2 batteries

We just purchased a Rockwood MiniLite 1905 last fall and are just starting our camping for the season. We will be boon docking most of the time at territorial camp grounds so we'd like a little bit of AC power for Keurig, toaster, etc. We have 2 x 12V AGM deep cycle batteries wired in parallel (I think, the dealer installed them).

My question is, as with our solar panels, do we hook up the positive of the inverter to 1 battery and the negative to the other?

We tried a 3000W inverter today and got the low power indicator by hooking it up the way the manual said, negative and positive to the same battery. I think perhaps the 3000W was trying to draw more power than the 2 batteries could supply. I don't want to take a chance wiring it wrong cause if I blow it up, I can't return it for a lower wattage one.

Any help would be greatly appreciated. Thanks!
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Old 05-20-2016, 08:29 PM   #2
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900w will pull about 70 amps for approximately 3minutes for a keruig. So depending on length of wire run, you would need to 6ga for 8ft and 4ga for over that length. And don't buy the stranded "speaker wire" they sell on Amazon- go to HD or lowes. Personally I think you don't have enough batteries but maybe someone with a better electronic mind can chime in.


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Old 05-20-2016, 09:05 PM   #3
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900w will pull about 70 amps for approximately 3minutes for a keruig. So depending on length of wire run, you would need to 6ga for 8ft and 4ga for over that length. And don't buy the stranded "speaker wire" they sell on Amazon- go to HD or lowes. Personally I think you don't have enough batteries but maybe someone with a better electronic mind can chime in.


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Thanks Hondaman174, will keep that in mind when we get the cables.
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Old 05-21-2016, 12:47 AM   #4
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How much battery capacity do you have?

Also, are you wiring your inverter into your main fuse panel? If so, make sure the fridge is on propane only and your converter/charger is also disconnected so it isn't trying to charge the batteries with inverter (battery) supplied alternating current.

I would recommend ditching 12V batteries and going with 2 decent golf cart batteries. You'll easily double your battery capacity and ability to draw larger loads.

I would not use anything thinner than 0 gauge wiring when connecting batteries together and running wire to an inverter. My personal RV system is 2/00 thicker cable for all battery and inverter wiring.
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Old 05-21-2016, 06:46 AM   #5
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We tried a 3000W inverter today...
The wattage of the inverter will eventually make a difference, but when you tried it, what was it supplying power for? Others are correct in that it can draw a lot of power, especially considering the two devices that you indicate you want to run. Keurig will take between 800 and 1500 watts and the toaster is probably about the same. Be aware that is at least 125 amps of 12 volt. Neither of those loads is small, both would probably run the chance of topping out your 3,000 watts. The Keurig, depending on the model, will draw 60 to 100 watts all the time if you are keeping the water "ready for coffee."

Modern inverters are good, but they do require a lot of 12 volt to run.
What size wire did you use to connect the inverter when you were trying it?
What loads were plugged into it?
If you are trying to power the entire TT and have a converter you need to turn it off (breaker or unplugging)
It is true that when connecting loads to 2 parallelled 12 volt batteries, the positive should go to one of them and the negative to the other, but that is how they should already be hooked up to your unit.
if you drink a lot of coffee and love your toast, 2 -12 volt batteries really will not do you well for more than very occasional usage.
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Old 05-21-2016, 07:42 AM   #6
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It really does not matter how big your inverter is; without the battery capacity to maintain voltage during its use will cause it to alarm and drop off line.

Trying to pull 100 amps of 12 volt power (1200 watts) from a single battery can instantly collapse the voltage below the low voltage cut off. With a pair you spread the load over two batteries and cut the voltage loss more than half.

Even at 50 amps per battery, the capacity loss is substantial and you will not get the power you need for the balance of your day without recharging (especially if you expect to use heat at night).
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Old 05-21-2016, 09:17 AM   #7
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Here's an option for you:

Many electrical units say on them how many watts they pull. Once you know that (or from manufacturers site may have to convert amps into watts) you know what sized inverter to get. Now, do you have room underneath your rear seat of your tow vehicle? I installed a 1000w inverter to power my 120v tire inflator as there will be times I will not be bringing a genny. That way I can plug in a extension cord and change tire inflation anywhere around TT. It pulls 6amp ac. Converts to about 700 watts. No problem. I even have a 4hp vacuum that pulls 900w. Ran two lines of 6ga (cause 4ga was too difficult to work around the interior) and only had a voltage drop of .1 volts and that was with wire from HD or Lowes. The cheap stuff from Amazon would instantly go to low voltage during testing. Connected to battery with 100amp resettable circuit breaker as those glass fuses delve loped their own problems after heavy use. Turn on the truck and there you go. Have been know to cook a crockpot meal while driving to destination.


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Old 05-21-2016, 12:38 PM   #8
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This site worth a look especially if you are not planning to or have not decided on powering your entire trailer or just running a dedicated line or two from your inverter.

For a small system that is budget minded and easy to install I like his approach to it.

There's some good information and videos to give you some ideas.

Welcome to Love Your RV! | Full Timer RVing Blog

1000W Pure Sine Wave Inverter**Updated*
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Old 05-21-2016, 01:40 PM   #9
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Here's the answer to your problem with no math required:



Then enjoy your boon
docking with no worries of power.

Enjoy.

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Old 05-21-2016, 02:23 PM   #10
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Here's the answer to your problem with no math required:



Then enjoy your boon
docking with no worries of power.

Enjoy.

My husband swears to this coffee pot. He won't even let me buy a bigger one.
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