Running A/C off new large lithium battery

[Ken_Judy]

Hi guys, the 4 AGM’s on my 2018 Oliver are kaput. I am installing a new Vatrer 460ah and was wondering how hard it would be to run the A/C off of it. I know I would need a 3000 watt inverter. Would I just take the A/C wires off the charger/converter and make a plug that plugs into the new inverter?  Thanks

[Ronbrink]

You will need to install a dedicated automatic transfer switch to be able to run the a/c off the batteries via the inverter and still be able to operate it when on shore power. No need to upgrade the inverter just to be able to run the unit in this manner. You will also need to install a shunt and fuse with the battery upgrade. Search ‘Ollie Modifications’ for owner write ups to glean information and install details.  Here are a few pics on the required ATS to get you started:

My install.

Pic provided by another illustrating the wiring.

ATS wiring diagram.

Edited 11 hours ago by Ronbrink

[jd1923]

On 10/2/2026 at 3:00 PM, Ken_Judy said:

Hi guys, the 4 AGM’s on my 2018 Oliver are kaput. I am installing a new Vatrer 460ah and was wondering how hard it would be to run the A/C off of it. I know I would need a 3000 watt inverter. Would I just take the A/C wires off the charger/converter and make a plug that plugs into the new inverter?  Thanks

These Vatrer batteries should be a good choice, great $/Ah cost! I was hoping to see somebody go this direction.

You should know only one (1) of these will fit in the battery bay, so no room for future expansion with one 460. You could install 2-3 of their 300 Ah batteries instead, for more money of course. Either way, none of the Vatrer choices fit in the MORryde battery tray except for one 300.

Running A/C? Ron is correct in that adding the 20A ATS, RV A/C can be run on a 2KW inverter. He has his working well, I tried it and then upgraded to the Victron 3K inverter. There are other considerations. 

I'm thinking since you currently have AGM batteries, maybe you have the Dometic Penguin II A/C?! If so, this beast of old pulls 150A when running, which means that for every hour you run it you're using 150 Ah of your LiFePO4 batteries. On a 460 AH battery running the old P2 will reduce SOC by 30% every hour, just 3 hours to a dead battery.

First you want more Ahs if you truly want to run A/C via the inverter! Many Oliver owners have installed better A/C units; the Truma, Dometic Freshjet, Houghton and Tosot. They are about 40% more efficient, so instead of 3 hours, 460 Ah should last 5 hours. These A/C models all have single-speed ON-OFF compressors, that run ON most of the day when hot out.

If you install an inverter-compressor A/C like Turbro, Pioneer, etc. or the variable-speed Chill Cube these numbers improve greatly. We have 900 Ah and the Furrion Chill Cube A/C. I had no idea the numbers would be so good. I ran several tests and on average we used 200 Ah to run this A/C for 24 hours, on a sunny day in AZ with a high of 93F. The 320W rooftop solar was also adding power which likely added another 120 Ah/day +/-. But I ran our Chill Cube A/C all day on battery for what the Dometic P2 would have consumed in 90 minutes! I ran tests for two weeks at home and since have used the new A/C about 8 days on 2 camping trips.

To run A/C regularly on inverted power you need enough Ahs, say 600 min, 900 Ah better! You need an efficient A/C unit, otherwise the idea is not viable. For occasional use, upgrade per Ron's suggestion. Want to do this regularly, upgrade your inverter to a 3KW model.

I had no idea it could work this way. It took 3 years of upgrades with some trial and error!

With the DC-DC charger going, we can leave home with a full charge, run the A/C while we're towing. Have a cool cabin for bathroom and lunch breaks on the road, and arrive at the campsite cool with near 100% SOC. The DC-DC charge of +40A is about what the A/C uses during the day. The rooftop solar adds enough the run the fridge, etc. If it's cold out and no need for A/C, we sometimes heat the hot water tank on electric! Or if we've been boondocking for a few days the DC-DC charger brings our SOC% up considerably for the next stay. 😎 

Yeah, it's a can of worms where one upgrade may lead to the next, to the next, to the...