Running Air Conditioner off Lithium Batteries

RFraer

I attended  Ucamp22 this years and camped in the boondock section. Last years i upgrades my batteries (SOK 618 amp hrs ) and inverter so that i could run the Air Conditioner (AC) off-grid.

At Ucamp during the battery presentation NuCamp and Battleborn announced that starting with the 23 model years they will offer several lithium battery options.

The higher options will be capable of running the AC unit in the 400, 320 and the truck campers. From the information they provided the upper level system is similar to the system I installed including the Victron Multiplus 3000 inverter / Multi Control and BMV-712.

I know this battery upgrade will only interest a small percentage of campers but I thought i would share my limited experience .

Because these off-grid AC battery systems are new I notice there was some misconceptions by the audience at the battery presentation on what the systems can and cant do. For example you probably cant get rid of the gas generator or the system is set and forget like the smaller lithium systems . Also the systems do not generate 1 watt it is only for energy storage, you need a generator, solar or the tow vehicle to generate power.

I am still new at using the off-grid system and the six days at Ucamp was one of my first opportunities to use my system for an extended period in hot weather..

I primarily ran the AC on battery at night during quite hours when generators were not allowed. I ran a Honda 2000 during the daytime to charge the batteries and run the AC.

When the AC was cycled on the Honda put about 1200 watts into the camper and 600 watts into the batteries. When AC cycled off 1400 watts went into the batteries and other small loads in the camper. These numbers include on average 100 watts from solar.

On the hottest Ucamp night running the AC at a comfortable 77 degrees I had 15% battery left in the morning. That does not include 20% I set have set as battery reserve and could be used if needed.

One area that I have found essential to keeping my system charged when traveling is the addition of a DC-DC charger. The wattage from the 7-pin would take days to charge my batteries. I am using a Victron Orion-Tr Smart 12/12-30A DC-DC charger. I am running 4 AWG wire from the vehicle battery / alternator with a 60 amp fuse to a female Anderson connector on my bumper. The male connector on the camper goes back to a DC-DC charger delivering 360 watts. With the DC-DC charger, solar, and 7-pin I am getting about 500 watts put into the batteries for every hour my tow vehicle engine is running.

These are the pros and cons the I have experienced for my system so fare.

Pro:

It is more comfortable to stop at Cracker Barrel, Walmart or Harvest Host on hot nights, A campground with electric is not needed. (this is the main reason I upgraded)

Stopping at rest stops or having lunch is nicer on hot travel days.

With the hybrid inverter you can use a smaller generator. If the inverter needs more power when the AC turns on it will take energy temporarily from the batteries, this also eliminates the need for a AC soft start device.

The Multi Control on the Multiplus allows you to control the amp draw of the inverter. If you moochdock at a friends or relatives house you can set the amp draw below the circuit breaker amp rating to prevent tripping the breaker on 15-20 amp house circuits take energy temporarily from the batteries.

Use less fuel running the generator. When the AC cycles off the energy goes into the batteries. Also I run the system primarily at night so the Generator is not needed then.

When boondocking and not using the AC on cooler nights I can run the 3-way frig or Alde on 120V ac to save propane.

Cons:

Cost, my DIY system was over $5000. (No pricing was given for the NuCamp Systems.) Running a generator would be more cost efficient but not as convenient. I did it because of the convenience and I am retired and needed something to do.

The 200 watts of solar on the camper is just a trickle charger for the 600 amp hr batteries. To have any charging significance much more solar would be needed. I have charged with 600 watts of solar panels (400 watts going in on average) It would take approximately 18 hours to get my batteries to fully charge (float).

Significant air flow is needed to cool the batteries and inverter under the bed. I have not noticed any heat coming through the bed but I am in the process of upgrading the cooling fan and ducking on my system. I will see how much fan noise I get.

You can run the AC and Microwave but not at the same time.

You have to monitor the system more to see your state of charge. To run the system all night the batteries have to be full or close to it. Like with an electric vehicle you can get range anxiety.

Dutch061

Thanks for the great feedback, I have pondered adding a Multiplus 3000 in place of the factory 1200-watt inverter and my 60 Amp PD Converter and have kind of talked myself out of it. Not sure I could get through the night with 400 Ah of batteries based on your consumption experience. Plus, I hadn't considered the heat generated by the Multiplus 3000, which I am sure is substantial especially when combined with the average 50 Amp draw (8 hours x 50 = 400 amps) and heat produced by the batteries.

I have also pondered getting something a little bigger (read as larger but not huge) than the 400 but have failed to find a suitable replacement that is enough to make much difference. I would still likely have a wet bath and also still have to crawl over my wife to get out of bed.

So, I think the answer is to change up a couple of things we use by swapping-selling and adding different items back. I can do that for less than $2K which won't even put a dent in trading campers! I always have a generator with me anyway, and we try to stay in higher elevations or more northern climates through the summer which is a big help!

Brad

Denny16

Brad, I also find RaFaer’s comments interesting, I had already heard nüCamp was looking to offer lithium upgrades in 2023 TaBs.  His findings are close to what I had worked out on paper, thst it would take a minimum 3K inverter and 600AH of lithium batteries to run the CoolCat overnight, adding a Soft Start will reduce the initial power dran at startup and save some amps of battery use.  

That said, I have come to the conclusion this upgrade for our camping style is too much, cost and size wise, for the small return.  Since we camp mostly along the Northern California coast, where it cools down most nights, running an AC at night is not necessary, or needed.  We do not have AC in our home either, and do not need it.  

Quickly I discovered the stock 1200/1800 PureSine inverter was not up to running the one AC appliance we do like to use, a microwave oven.  The stock inverter would not even run the smallest microwave oven we found.  Doing the math, I determined I would need a 2K-watt inverter and 300AH of AGM or 200AH of lithium batteries to run an average small microwave, and induction cook top (not a fan of using the propane stove in the small cabin space of the TaB).  

A 200AH/2K inverter setup would not take up much more space than the existing 200AH AGM battery setup.  The 2K-watt inverter is only a little larger than the existing 1200/1800-watt inverter, and is doable cost wise, especially if done in stages.  Our existing 190-watts of solar keeps our current AGM battery charge running the AC/DC fridge overnight, adding 100 or 200-watts of portable solar would keep a 200AH or 300AH lithium battery bank charged for our average use whilst Boondocking, including using the microwave and an induction cook top for reheating food and making coffee.
Cheers

Dutch061

@Denny16, we still carry our portable Camp Chef stove, and we cook outside to keep the heat (and odors) down inside, plus it is a 15K BTU per burner stove. So, it is a lot higher heat output than the Dometic cook top installed in the 400. We rarely use the microwave, instead opting to use it mostly to store the loaf of bread in.

We are in a rare (at least for us so far) situation where we have been volunteering since May 1st, our compensation being a campsite with full hookups. My wife has become used to being able to take long showers and use the microwave, but the switch back to boondocking will happen July 1st as we start to move back to our more normal routine. 

There are so many options available to do different things, it really boils down to what works best for each individual. We have only had to use the air conditioning 2 nights where we are at (western SD) but the thermal load during the day (due to zero shade) has been a challenge to keep the inside cool even with the A/C. 

I spent 7 days boondocking in the Outer Banks in March, and still had about 30% SOC in my 400 Ah of Battleborn, so I am very pleased with that. To really optimize my situation, I would need to add another 800 Watts of Solar Panels (Battleborn recommends 200 to 250 watts of panel per 100 Ah of battery) but have found that I would rather run the generator than to buy more panels and have to mess around hauling more stuff.

Brad

Denny16

Brad, we are both coming from similar starting point.  I also feel 400AH of lithium is the max for a small trailer like the TaB400.  I have already setup our TaB with 200-watts of additional portable solar (two 100-watt small compact panels, easy to store) using a second Victron controller networked to the factory controller for the roof top solar, so they work together.  For what we want, I think 200AHs to start will work, adding more lithium as we see what actual requirements are going to be with our average AC use requirements.  

Next item to get, is the 3K-watt inverter, then the lithium batteries, as needed.  Stay safe and have fun on the road…
Cheers

Dutch061

@Denny16, with the additional solar and sufficient sun you will easily get by with 200 Ah of Lithium. I was able to easily go 3 days with 200 Ah and little sun. I could even still use the inverter for coffee and toast on day 3 with 13% SOC remaining, which is impossible with AGM or SLA due to the low voltage at the SOC that would be present.

I could have added additional solar for less than the additional 2 Battleborn batteries but didn't want to haul more stuff and have additional things to set up when I got there. Yes, I am retired but I like the "set it and forget it" option I have with 400 Ah.

What brand-model of 3K Inverter are you looking at?

Brad

P.S. I would PM you rather than post on this thread, but I am not on your list of recipients.

manyman297

@RFraer How long are you able to run the AC at night?

With many of the 12v AC units coming down (kind of) in price I wonder if there’s a cabinet option (like the cool cat) in the works that could be a swap situation? I know the 12v units use almost half the wattage but aren’t as efficient at cooling vs 120v systems. 

But is there enough of a difference in price/effort to justify the 12v AC unit?

RFraer

On the hottest night at UCamp I powered the camper for about 11 Hours. The AC was cycling on about 70% of that time.

It would be nice to see a 12V AC unit that could be ducked but the ones I have seen are ceiling units. You loose efficiency when converting AC to DC and back. I have read that you loose about 15%. 

pthomas745

DougH in this comment ( he has commented about this before) describes his setup and the outcomes of running the AC on his AGM setup.

https://tab-rv.vanillacommunity.com/discussion/comment/155201/#Comment_155201

tomtek

We were out this weekend it was well in the 80's on Friday night.  I fired the A/C up after visiting with friends it was about 10pm.  inside temp cooled down fast and I planned on turning it off in a couple hours.   I fell asleep and it ran all night I woke up 3:30 am and the Battery was at 51% so I left it on.   When I finally got up at 7:30am I was down to 37% SoC.    

560aH Lithium with 1200 watt inverter and 300 watts of solar.   Since we were parked in a shady area I didn't get much solar the next day.  I started Sat evening at 40% with a little bit of charging when the Sun was going on and off the panels.

Sat night turned out cool so we didn't have a need to run the A/C.  I ran the MaxAir ceiling fan all night on Sat night and into the morning along with fridge and phone chargers.   Came home today ended up at 26% Soc


I feel Battery project was a success to be able to boondock and run A/C for short times. 

manyman297

@tomtek  You were able to run the AC on a 1200 watt inverter?

Denny16

Tomtek has a 2021 TaB320, with the Air8 AC, which has a lower current draw than the CoolCat.  I have wondered if the Air8 would run on a good, full 1200-watt inverter.  The CoolCat needs at least a full 2,000-watt inverter to run.
 Cheers 

manyman297

@Denny16
 Oh, gotcha.  

tomtek

manyman297 said:

@tomtek  You were able to run the AC on a 1200 watt inverter?

Yes also as others said I have an Air8 with relocated temp sensor.  Around 700 watts running.   I think a 1600 watt inverter would be a better choice for inverter cooling reasons.   The 1200 turns the internal cooling fan on at 50% load or 600 watts.   

RFraer

I wish the Air-8 would have worked in the 400. It is a great Air Conditioner to run on battery power.

Denny16

Yes, the Air8 seems it was designed for use in a RV, where the CoolCat is an adopted residential AC (older window style units which have been replaced by mini split heat pump units).  

@tomtek the optional running range of an inverter is normally 80% of its max load for bestselling efficiency.  Your 1200-watt running at 80% is around 900-watts, so the Air8 is in this ballpark.  Going to a bigger inverter is only going to increase the inverter cost and reduce its efficiency.  The fan running is not that big a current draw.
 Cheers 

tomtek

Denny16 said:

@tomtek the optional running range of an inverter is normally 80% of its max load for bestselling efficiency.  Your 1200-watt running at 80% is around 900-watts, so the Air8 is in this ballpark.  Going to a bigger inverter is only going to increase the inverter cost and reduce its efficiency.  The fan running is not that big a current draw.
 Cheers 

80% is the bang for the buck number and definitely a round about number I used to purchase it.    

Peak efficiency on small cheaper inverters is around 30% of max rated load.   Efficiency is very poor < 10% Load and a slow decline from 30% Load to full load.    700 watts * 3.333(for 30%) = 2333 watts for maximum conversion efficiency.  Any upgrade from 1200watts to 2333 watts increases inverter conversion efficiency.  But there is another variable impacting system net efficiency.   It's not the fan running its the heat generated by the case and also blown out the venting by the fan.    Temperature exiting the inverter and case temperature is measuring 105+ degrees which my Air8 must offset with added cooling time negatively impacting net efficiency.   In my case its in the drivers side under cushion which also contains convection slots for Alde heating putting the heat into cabin.  By increasing the inverter wattage will lower running temperature thus increasing my total system efficiency.   While I probably won't upgrade anytime soon.  I felt it was important info for others.