Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 11, 2025 ...

Air Conditioning Run on Lithium Powered Hybrid Inverters

July 02, 2020, 09:46:21 am

This question is directed to those who have switched to lithium batteries and hybrid inverters along with their solar.  How many have moved the AC to the inverter electrical panel and how many hours/day do you use this means of powering your AC...and how much of your lithium capacity is used...and how big is your lithium bank?  13.5 or 15 AC?  One or both units?  And how much solar do you have and how effective in replenishing power used for AC without generator?

Finally, I assume you can still run your AC off shore power or generator and how is this wiring accomplished together with the ability to run off the inverter?  We'll have 1200w of solar when we're done. 

Since we use our RV to escape heat we're just not sure how much we'd use this capability. Just trying to figure out how much extra effort/cost is needed to provide for the possibility.

Thanks

Quote Selected

Re: Air Conditioning Run on Lithium Powered Hybrid Inverters

Reply #1 – July 02, 2020, 10:26:52 am

In a previous thread on solar, someone had set their AC to run off the batteries.  I had run the numbers and not sure what he had but he was going to be eating into battery capacity  since he did not have enough solar to supply all that was needed.  An AC unit runs around 13 amps. which is aprox. 1560 watts. so if you have 1200w of solar you will have a downfall of 360 w.  Problems come in  that you will not be putting out 1200 w of solar plus power loss of the inverter..

Foretravel on the IH45's puts the second from front AC on an inverter and also install a large alternator.  With this setup you can run 1 roof AC unit while going down the road without having to run the generator.  AC unit does not take long to put a hurt to your battery bank without an outside charge.

Quote Selected

Re: Air Conditioning Run on Lithium Powered Hybrid Inverters

Reply #2 – July 02, 2020, 10:43:26 am

Randy, we have 1200 watts of solar, a Victron Multiplus Inverter/charger, a Victron Phoenix inverter and 600  amp hrs of LiFePO4 batteries.

A 1350 watt AC will not use that much all the time nor will it run all the time.  For the purposes of example lets assume it does. So 1350 watts at 13.4 volts from the batteries at 90% efficiency is 112 amps/hr.  If you have a residential refrigerator and use about 3000 watts per day for all other purposes (not running an AC) that is another 10 amps/hr.  So normal loads plus the AC will be about 122 amps/hr.  Using 80% of your capacity will get you just over 4 hrs of AC time.

Your 1200 watts of solar will get you on average over the year about 350 watts per hour or 22 amps for about 8 hrs.  Mid summer on a perfect day in the sun at 7,000 ft you might get 4-5 times that.  Typical summer days maybe 40-50 amps per hour at peak times. Mid winter maybe half.  It is good for recovery but not for running the AC.  These are averages, every day with solar is different.

The hybrid side of the inverter/chargers only adds some inverted power to the pass through power from the land line or generator assuming you are using the inverter's transfer switch.  The Multiplus will add up to 14 additional amps to get you up to 64 amps at the inverter sub panel.  All of that assumes you have made significant upgrades to the 120 volt wiring and circuit breakers to and from the inverters.

Inverting alone from batteries will get you 2500-3000 watts steady state depending on the inverter with more available for short term peak loads.

There are soft start add ons for the ACs that reduce starting loads.

If you are driving and have an appropriate charge while driving setup that adds capacity.  Most of your OEM cabling might need upsizing for those loads for continuous operation.

So it is possible to run one AC for a few hours from the batteries using the inverter with an appropriate setup.  The AC wiring effort is significant. It is mostly a power balancing problem, one with a not insignificant solution.

Quote Selected

Re: Air Conditioning Run on Lithium Powered Hybrid Inverters

Reply #3 – July 02, 2020, 11:39:09 am

I have 3320 watts of solar and over 30kwh of lithium batteries.  I can run both AC units (15's) while underway for I also have the Buck-Boost DC-DC converter 24/12 100A (12V Alternator Charge to 24V Lithium) supplying about 1200w to my battery bank.  My inverter/charger is a Victron Quattro 24/5000/220-100/100 120V Inverter/Charger.  In the summer, if it is sunny, I can run my AC units while underway and still maintain 100% on my battery power.  When we boon dock we have enough battery capacity to run one AC unit all night long so we can get a good night's sleep. We usually are at about 50-60% when we get up in the morning.  Our coach is all electric/diesel, no propane.  We have induction cooktop, GE Advantium, dishwasher, washer/dryer, and residential refrigerator that run on electric.  If the weather is mild and summer time (no AC required) I also run my AquaHot on electric, otherwise it is much more efficient to use diesel for the AquaHot.

AM Solar did the solar, lithium and inverter install for me.  When I stayed at Jojoba Hills RV Park in Aguanga, CA last winter I only plugged in twice at Thanksgiving and Christmas and the rest of the time my solar and batteries were sufficient.  I had to plug in for we had successive cloudy days in a row and we were cooking for multiple Thanksgiving and Christmas dinner engagements.

It is great not being a slave to the plug or having to run the genset.  I do still run the genset once a month to exercise it.

Hope this helps.  I am not an electronic whiz and that is why I had AM Solar do the install.

Safe travels,
Oscar

Quote Selected

Re: Air Conditioning Run on Lithium Powered Hybrid Inverters

Reply #4 – July 02, 2020, 12:27:07 pm

Just my Humble observation, it cost a lot of$$$$$  to run ac on batteries for any useable length of time,

Quote Selected

Re: Air Conditioning Run on Lithium Powered Hybrid Inverters

Reply #5 – July 02, 2020, 01:04:11 pm

Ya, the break even point is NEVER.

Quote Selected