Inverter wiring in older Montana

[jfaberna]

I'm trying to setup my Montana so I can boondock 1 night at a time at places like Harvest Host.

I'm wanting to do this on a budget, so I'm not interested in putting a ton of Amp Hours in the battery bank or megawatts of solar panels on the roof.

I currently have a Norcold RV fridge that has been converted to dual compressor 12V. This is very efficient. This is the only thing of significance that draw power while going down the road. My 500 watts of solar panels can and does run the fridge and charge the battery while traveling on a sunny day.

I plan on replacing my 210 aH flooded batteries with Lithium soon but this is enough to run the fridge and CPAP machines and a few light overnight when 120VAC is not available.

However, I'd like to add a 3000W inverter and about 230 aH of LFP batteries which should get me by for things like the toaster, coffee pot, and maybe short runs of the microwave.

The budget inverters I'm looking at have recepticales and terminals to wire in 1 leg of 120VAC. I saw a video recently where the dude just wired up a cord that plugged his inverter output to his shore power connector using an extention cord with the appropriate adapters. All he had to do was turn off the panel breaker switches for the air conditioner and battery converter and then he could use any 120VAC device in his RV as long as it didn't exceed 3000 watts and his battery capacity.

This sound like a simple and cheap way of doing it and for me it might be simpler because I have a front mounted 50 amp shore power connector as well as the usually rear one along with a ATS.

I use the front 50 amp plug with an adapter to plug in my Honda generator when I'm at a place that allows generator useage. When I do that I also have to turn off the battery converter and air conditioner.

Any thoughts on this?

[Carl n Susan]

What you proposed is the quick and dirty route for an overnight boondock stop. The key thing is to remember to turn off the 120V for the converter, water heater, AC or other high draw equipment. And then, turn them back on before you leave.

Be sure to use a heavy duty extension code (min 12/3). A 3K inverter (or even cheap 2K inverters from HF) have 2 output receptacles. Most likely each only produces 15 amps (maybe 20 total?) of power. The Toaster, Coffee Pot and Microwave do suck power, but I have run the Toaster and Coffee Pot before for short periods. My Microwave is not hooked to my inverter.

Knowing the amp usage for what you plan to use/do is important. I use about 120 amps a day. but that is reoccurring and not for just a one night stop (which tends to be less).

If you are going to be boondocking more than one night, you might want to consider a slightly different, but still inexpensive, approach if it will work in your RV. I wanted to be able to run CPAP, TV, stereo, satellite, internet, and charge electronics with an inverter independent of everything else.

My model Montana has one circuit that feeds the entertainment center where everything I need (except the CPAP) resides. I ran a circuit from the inverter to a Double Pole Double Throw (DPDT) switch. The existing circuit was re-wired to also use the DPDT switch. The DPDT is right by the circuit breaker box so it was easy to change around. Now I can run the entertainment system stuff without having concern of firing up the generator and have to interrupt anything. I was going to use the second outlet of the inverter to power the CPAP but discovered a spare 600W inverter plugged into the 12V TV outlet in the bedroom allowed my regular CPAP to run perfectly (I don't use a humidifier which is too much draw). They make a 12V CPAP which is another option.

I use this setup for weeks on end. The entertainment stuff and CPAP run every day and I use the generator to charge the batteries, run the microwave when wanted, or other high draw equipment without flipping breakers, unplugging, or interrupting a TV/satellite recording.

[Daryles]

jfaberna,
For boondocking I have my inverter plugged into adapters and then into the shore power connector.
I turn off ALL my breakers (except for the 50A main). Switch the fridge to propane mode.
I only turn on the breaker for the appliance I'm using (microwave, coffee pot, entertainment center, AIr Conditioner). Then turn it off when I'm done so it's not inadvertently turned on if something else is running.
As long as we stay below 3000w, we're good.
Spent two months dry camping in Canada this summer managing power consumption like that. Worked fine.
When I get home I am going to add an ATS. Switching back and forth manually is a pain.

Also look at adding a DC-DC charger. It's a good backup for when solar isn't working.
https://www.montanaowners.com/forums...hlight=charger

[jfaberna]

Originally Posted by Daryles

jfaberna,
For boondocking I have my inverter plugged into adapters and then into the shore power connector.
...
Also look at adding a DC-DC charger. It's a good backup for when solar isn't working.
https://www.montanaowners.com/forums...hlight=charger

So it seems I will not be alone if I take this route of pluging the output of the inverter into the front shore power connector with adapters. I might be able to improve on that a little.

You mentioned the DC-DC charger and that brings me to the standard 7-pin trailer power connector for lights and breaks. I get about 5 amps of power that way, but when I convert to Lithium LFP batteries I wonder what to do.

Is the truck power connection even work at that point or do any harm?

[Daryles]

There is a YouTube video showing an alternator burning up while charging a lithium battery BUT, it was done on a bench, no Airflow over the alternator. Also, it's at least 24' of 10 gauge wire between the alternator and the lithium house battery in a 5er.
The most I have actually measured going through that wire was about 7A. The batteries were at 30% so they should have been pulling pretty hard.
On top of that in my truck, that charging circuit is on a 30A fuse.
I left the charging wire connected in the 7 way cable.