Good morning, Dave,
I am considering upgrading the Roadtrek’s batteries to lithium ones, but I’m uncertain if the vehicle can accommodate this upgrade. Additionally, the generator has suddenly stopped working and isn’t producing a spark.
If I proceed with the lithium upgrade, my primary concern is ensuring that the battery bank can run the air conditioner. For your reference, I have the green Roadtrek solar charge controller.
Thank you for your assistance.
Best regards,
Othmar, 2015 Roadtrek 190 Popular w/solar
Hi, Othmar,
You did not specify if you plan to be boondocking or dry camping. I will assume you will not be plugged into shoreline power to provide 120-volt power to the roof air conditioner since you were concerned about the batteries providing power to the roof air conditioner.
Calculating battery power needed
There are several variables in the calculation of what battery power you will need. According to the spec’s I can find, your unit has a 10,200 BTU air conditioner. That is a little more efficient than the larger units, but it also depends on the ambient temperature and how often the air conditioner will turn on or “cycle”. However, the unit is only 20’ long, so there isn’t a large amount of cubic feet that needs to be conditioned. There are other 12-volt components that need to be factored into the equation, as well.
According to your photo, the Lifetime batteries are AGM. However, I cannot see the amp-hour rating, but they will only have a 50% capacity. According to the specifications, your converter/battery charger is a 45-amp model.
Swapping lithium for AGM batteries
We have covered this before, which you can find more detail here. However, the quick overview is the converter in your rig will only charge 13.6 volts until the batteries get to 12.6 volts, and then drop to 13.2 volts. Most lithium batteries require 14.4 volts to 14.6 volts for two hours, so the charging profile you have will only charge the batteries to about 60%.
You indicate the unit has solar but not what size or model, and I am not sure what model the green controller is. With a short unit like this, I would assume it is a single 100-watt panel that is designed to keep the batteries topped off during storage but not large enough to provide the charging capacity you will need.
Running roof air conditioners off-grid
Your 10,200 BTU roof air conditioner runs on 120-volt power. To run it off-grid you will need an inverter to pull 12-volt power from the house batteries and provide 120-volt power. The first issue is the roof air conditioner is wired to the distribution center with a circuit breaker. You would need to rewire the system to have a 120-volt wire coming from the inverter to the roof air conditioner. Since it is not plugged into an outlet like a refrigerator or TV, the Romex wiring would need to be hard wired.
I do not know the exact “math” of the power draw of the 10,200 BTU roof air. However, Keystone has a system called SolarFlex which uses a set of lithium batteries, solar panels, and inverter to go totally off-grid. During a demonstration at the Hershey RV Show, they had 600-watt solar panels, 600-Ah batteries, and a 2000-watt inverter and could only run the roof air for about 2 hours.
Calculate power usage
I would suggest looking at what other components would be using 12-volt power such as the lights, water pump, and refrigerator. The spec’s show your rig does have an absorption refrigerator, so you can run it on propane and limit the 12-volt draw. Go Power! has a good calculator on their website here.
It is not a perfect science as it is hard to determine how often you will use the lights, when LP appliances will cycle on, and other power draws. However, it will get you started to think about 12-volt usage and how much battery power and solar you will need.
In my opinion, it will be very difficult to run the roof air conditioner “off grid”. You will most likely need to get the generator running to help supplement the batteries. However, without more information I am unable to diagnose why it’s not running.
You might also enjoy this from Dave
What monitor do you recommend for lithium batteries?
Dear Dave,
I’m looking for a meter that will indicate the remaining charge in my lithium battery. I picked one up that said it would work but it always reads 100%, even after a couple of days of use. Any suggestions? 2019 Wolf Pup 16FQ, with an updated charge controller for lithium batteries. Thank you. —Ray, 2019 Wolf Pup 16FQ
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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I had a 2016 Roadtrek SS Agile. Stock batteries are AGM’s and had a Progressive Dynamics inverter. Can’t remember what the solar panel output was. When I went to Quartzsite a couple of years ago, I consulted with one of the prominent solar companies there. The cost to run new heavier Romex wire plus the new inverter and batteries cost discouraged me to the point where I couldn’t afford to get the conversion done.
One other thing about inverters. Some have modified sine wave outputs. Only the high end ones produce a pure sine wave. Most inductive loads, like the compressor in the A/C unit may have a problem with the modified sine wave. Overheating and shorter lifespan.
I’d check to see if the generator has enough oil
My Oman emerald is touchy a little extra and it runs
Without enough no spark. Just my thought
Thank you, Dave, for the reminder of all the moving parts involved in switching to lithium batteries and running an AC unit. Have a great week!