I have 3 inverters that I can use for my travel trailer. A 2000,1500, and 350 watt. Also 2-12 volt interstate batteries for storage. It would be nice to use appliances en route or overnight. Use the refrigerator on electricity instead of propane while traveling from place to place or, microwave before disconnecting as long as the tow vehicle is connected and running to keep from having to connect and use my gas generators. I can see using a small medical device for a longer period, say over night.The placement for this would be stationary in the bedroom. Since using the refrigerator and microwave would be high usage, I'm guessing that the 2000 watt would be best for that as I would not be as concerned about energy usage. Placement for that would be in the kitchen area in the same area as the converter. For the bedroom, I could run a 12 volt wire from the battery or hook into an existing 12 volt light and mount on wall in bedroom. I would use this separate as it uses less energy and would make the 2-12 volt storage batteries last longer. I guess what I am asking is how to run/connect it all together and how to separate each inverter for the system for uses I envision. Perhaps I have it all wrong and there is another way to do this?Thanks for any help!

350 watt is fairly easy install next to the power distribution and converter area. Use the main 12v power feed to get 12 volts from the battery and use a small transfer switch to power the branch circuit of outlets. 350W should power the absorption fridge heater.1500/2000 watts really needs more battery and needs short heavy wire direct to the battery. Then you pull 120v wire to the power center and again use a transfer switch to power the branch circuit of choice such as the microwave. Microwave far prefers a sine wave inverter.And yes my RV is wired like this.

The not very big Servel S630 fridge in our C pulls at least 360 watts on start up using 120v, and then as the heater warms up the watts drop off somewhat to under 350. A 350w inverter will have a continuous rating of maybe 300? So I wouldn't count on a 350 to run the fridge on 120.

You say you like to run the fridge on ac on the road so I assume you have a two way.Running an elect/propane fridge on AC draws about 350 watts at a 50% duty cycle. So to run it overnight your going to need a lot more battery.

I'd wire up the 2k whole-house and be done with it. The small amount of 12v you'd save with the separate installs is minimal. 2 12v batteries is not much when running the MW.

A others have said, use the larger inverter and mount it near the batteries. https://www.altestore.com/howto/recommended-inverter-cables-sizing-and-breakers-or-fuses-a62/Cable sizes listed are for runs under 10 feet.

Multi Inverter use | Good Sam Community

2oldman
Explorer II
Jan 03, 2019
BFL13 wrote:
I went all big inverter, but lately went back to using a small one as well. The big one is whole house, which includes the seldom used TV which stays on standby drawing amps unless unplugged. ...
Easier to use a small inverter for phone charger etc, and turn off the big inverter except when needing it to do something temporary.
My entertainment is turned off with a switched extension cord nicely hidden in a cabinet ( I don't like cord mess.) That can be a significant draw overnight. My big inverter is *never* off.

With more than one inverter, your job is to keep turning them off and on as necessary. Not my style, but hey, if it works for you..!
time2roll
Nomad
Jan 03, 2019
My small inverter basically just runs. Large inverter is for temporary use of microwave or anything else large. Not a huge deal but gets turned off when not in use.

Next RV will have a big lithium battery and I will not care so much either.
pianotuna
Nomad III
Jan 03, 2019
Hi,

The alternator won't keep up because it "reads" the chassis battery. When that is fully charged, output drops. There are ways around that problem, such as adding an external diode for the "house loads" on the alternator. Too much trouble for me to bother with. A 2nd alternator would work well, too. But that is quite costly, and leaves one with a non standard serpentine belt.

RLS7201 wrote:
wa8yxm wrote:
One thing I found when running an Absorption fridger on the inverter (That is an option in this RV) is that the alternator does not provide the house batteries with enough current to maintain them at that high a load. Sorry.

Most RV fridges are 300-400 watt on A/C (And I also have some parasitic loads like the TV/Radio/Sat receiver (no more) and so on) The alternator could not keep up. Run it on propane and be happy

Residential run 100-200 watts now days That it can handle.

Or a high effiency (50 watts and it runs on 12 volt).

Your alternator should be about 130 amps at 1500-1800 engine RPMs.
If it won't keep up with 360 watts, you have a problem.
Properly functioning gas coaches will keep up with running an absorption refrigerator on the electric heaters.

Richard
pianotuna
Nomad III
Jan 03, 2019
BFL13,

360 watts at what voltage? Many small inverters do not do 120 volts--that makes a big difference to heating device demand. (power (wattage) changes by the square of the voltage).

Example:

120 volts vs 110 volts. Wattage would drop about 16%

360 watts x .84 =~ 302 watts

That will still demand about 30 amps from the alternator--which just isn't going to happen with 'stock' equipment once the chassis battery is charged.
BFL13
Explorer II
Jan 03, 2019
I got the 360-under 350 watts when starting the fridge from my inverter gen and reading from the Kill-A-Watt. Don't have the voltage now but would have been 124-122 ish.

In this case it would be from an inverter, which will add amps as battery voltage declines over time to maintain the watts. A MSW inverter is ok for a heater, so you would need a special voltmeter to get that voltage.
wanderingbob
Explorer II
Jan 04, 2019
I do not believe it was said whether the refrig was a household , 117 volt refig or a RV refrig, it will make a difference when allocating all those watts , volts and amps.
burningman
Explorer II
Jan 13, 2019
The alternator will make plenty of power for the fridge.
The problem is the wiring. Your camper charge wire, through the 7-way RV plug, is only 12-gauge at the largest.
The way to get enough power to the camper for running loads like a refrigerator or charging batteries a whole lot faster is to run a separate, large gauge charging wire.
Sometimes I do this simply by buying a set of 25’, 2-gauge jumper cables and cutting the clamps off.
Put lug terminals on and connect to your truck battery, run it to the trailer.
Use an Anderson connector, it’ll handle 100 amps.
Run similar cable to your camper batteries.
It’s not a bad idea to put a 100-amp circuit breaker at the beginning of the cable near the truck battery.

Getting DC power across wires at low voltage is all about wire size.
Bigger is better.

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