Power Off the Grid

[Grfrancis]

Is it possible to provide AC power to your RV through the power cable from an inverter that is powered by your onboard battery bank ?

[capt fast]

I wouldn't say no. but then...if you do, pay attention to your comp insurance fine print about systems modifications coverage.
disconnect the AC to DC inverter before you try that. could cause a fire or blow up something.inverters DC to AC are not very efficient but yes, it would work. but not for long. lead acid batts have low energy density.
I am waiting for tesla to build an RV coach battery pack with cooling that manufactures can build into the vehicles. that would be sweet. a LiOn pack could be custom built to do the job. needs more research. have seen many ideas and builds on youslesstube about it, but nothing about current limiting and heat dissipation while charging/discharging the batteries. may be some problems there for the home brew experimenter.

[astrocamper]

The larger inverter/chargers have an integrated transfer switch. Functionally the outside power plug feeds the inverter/charger transfer switch and the output of the transfer switch feeds the trailer main 120 volt breaker panel. This is how I wired my Victron Energy Multiplus 3000VA inverter/charger. All my 120 volt circuits can be powered by the transfer switch, just not everything at once.

[twinboat]

Yes you can, BUT you need to turn off your onboard charger.

The charger will draw from the inverter to try and charge the batteries powering that inverter. A loop that will kill the batteries.

Of course, to run everything, you will need a huge inverter and larger battery bank.

If you have a gas/electric fridge, switch that to gas to save battery power.

[Persistent]

Good advice above!

Nothing says you can't manage all this manually, but sooner or later, a mistake is likely to happen. Most people choose to have either dedicated outlets, or a built in transfer switch.

You must do some planning. It is necessary because of the limitations of batteries and inverters. List the 120 volt AC devices you wish to run and for how long you expect it will run each battery charge cycle.

We can then give more specific advice.

The proposed system must consider how to manage the built in battery charger as mentioned above.

The battery bank needs to be large enough to support peak power draw and large enough to sustain power delivery through a battery charge/discharge cycle.

Strategies that tend to work:

A small inverter system may have its own dedicated electric outlets. Plug in to dedicated outlet to run an appliance on the inverter output. Plug in to existing outlets when on shore power.

I have a 1000 watt inverter I run in this way. I charge computer and phone batteries and have on occasion run a CPAP machine.

To use the existing electric outlets in the RV, it would probably need a 2000 watt inverter or bigger. A minimum 400 amp hour lead acid battery bank would be required to support a 2000 watt inverter.

The built in battery charger must be turned "off" when inverter is in use. Air conditioning or electric heaters would not be usable using such a small system.

This tends to work better if the inverter has a built in "transfer switch". It would switch from shore power to inverter and disconnect the built in charger automatically. It also needs to "bond" the system ground and the neutral wire from the inverter. It would remove the bond for shore power use.

A bigger battery bank and inverter would be needed to supply all RV 120 volt appliances as they are normally used. Running high power consumption appliances like air conditioning would require an obscenely large battery bank.

I wish you good luck and happy trails ahead!

[TravelSolo]

Originally Posted by Persistent

Good advice above!

Nothing says you can't manage all this manually, but sooner or later, a mistake is likely to happen. Most people choose to have either dedicated outlets, or a built in transfer switch.

You must do some planning. It is necessary because of the limitations of batteries and inverters. List the 120 volt AC devices you wish to run and for how long you expect it will run each battery charge cycle.

We can then give more specific advice.

The proposed system must consider how to manage the built in battery charger as mentioned above.

The battery bank needs to be large enough to support peak power draw and large enough to sustain power delivery through a battery charge/discharge cycle.

Strategies that tend to work:

A small inverter system may have its own dedicated electric outlets. Plug in to dedicated outlet to run an appliance on the inverter output. Plug in to existing outlets when on shore power.

I have a 1000 watt inverter I run in this way. I charge computer and phone batteries and have on occasion run a CPAP machine.

To use the existing electric outlets in the RV, it would probably need a 2000 watt inverter or bigger. A minimum 400 amp hour lead acid battery bank would be required to support a 2000 watt inverter.

The built in battery charger must be turned "off" when inverter is in use. Air conditioning or electric heaters would not be usable using such a small system.

This tends to work better if the inverter has a built in "transfer switch". It would switch from shore power to inverter and disconnect the built in charger automatically. It also needs to "bond" the system ground and the neutral wire from the inverter. It would remove the bond for shore power use.

A bigger battery bank and inverter would be needed to supply all RV 120 volt appliances as they are normally used. Running high power consumption appliances like air conditioning would require an obscenely large battery bank.

I wish you good luck and happy trails ahead!

It all depends on how long you want to run those systems and if you have any supplemental charging capability like solar or even a DC-DC charger.

The biggest concern for using an inverter to power via the trailer cord is forgetting to turn off the converter. As noted above a transfer switch on the AC side cutting power to the converter is best if you do not install an actual inverter charger.

[astrocamper]

With an inverter/charger transfer switch there is no reason to keep the converter active in the circuit since the charging function is now provided by the inverter/charger at a potentially higher charge rate when plugged in. Many people also install substantial solar to provide charging that can supplement or replace the need for a generator when off grid.

I unplugged the 120 plug from the converter but left it in place because there wasn't room to easily remove it. Since it is unplugged it has no effect on the 12 volt circuit.

[TravelSolo]

Originally Posted by astrocamper

With an inverter/charger transfer switch there is no reason to keep the converter active in the circuit since the charging function is now provided by the inverter/charger at a potentially higher charge rate when plugged in. Many people also install substantial solar to provide charging that can supplement or replace the need for a generator when off grid.

I unplugged the 120 plug from the converter but left it in place because there wasn't room to easily remove it. Since it is unplugged it has no effect on the 12 volt circuit.

That is what I did/ Installed a 3kW inverter charger to power then entire trailer (its a small 30amp trailer) and removed the factory converter completely. Wish I had the room for more solar but I am basically maxed out at 400W on my roof.

[Bobby F]

This is sort of the default way that older rigs are re-wired to accept solar and multiple batteries.

It's how I do it on my rig. Works great. It's just like I was plugged in. (But if you run your microwave and watch your power meter, you'll be amazed how fast it goes down. And, I wouldn't even try air conditioning unless I at least tripled my batteries and solar panels.)

Just make sure you unplug or turn off your converter (which is simply a battery charger, converting AC to DC and feeding it into your batteries.) "Batteries trying to charge batteries" only makes heat out of your power and will discharge your batteries very quickly.

[Triangle Drifter]

Originally Posted by twinboat

Yes you can, BUT you need to turn off your onboard charger.

The charger will draw from the inverter to try and charge the batteries powering that inverter. A loop that will kill the batteries.

Of course, to run everything, you will need a huge inverter and larger battery bank.

If you have a gas/electric fridge, switch that to gas to save battery power.

THIS

You need understanding of which breaker powers what. If it chills or heats something it is a big power hog and will kill your battery bank in a hurry.

[Grfrancis]

Thanks everyone for the solid advise. Last question ... does the onboard battery disconnect switch disconnect the batteries from the onboard converter ????

[Bobby F]

Originally Posted by Grfrancis

... does the onboard battery disconnect switch disconnect the batteries from the onboard converter ????

I've seen them wired both ways. You just have to trace your own setup.