I'm on my first camping trip to a State Park where I have shore power and water hookups. This is my first opportunity to test my new Lithionics 315ah battery, Xantrex 3000w Inverter, and my Dometic 13,500 btu Penguin ll air conditioner with the added EasyStart module. When I started my "How long will the 315ah battery run my air conditioner?" test, it was 78° degrees outside and over the course of my testing the temperature increased to 85°(Real Feel 89°). I had the thermostat set on 75° at first but then as it got hotter outside., I put it down to 74°. I had less than 10a solar contribution. The sun was shining on the passenger side and directly on the inverter compartment. My Isotherm compressor refrigerator ran during the test as well (power usage 2.5a on average). I was able to run the air conditioner for 4 hours before switching back to shore power. I switched back to shore power when my Lithionics 315ah battery was at 21% SOC and Time Remaining was 33 minutes, at my current usage rate. So I could have continued to run the AC even longer. I did learn a few things that are significant and had to make some inverter settings changes.
1. The Lithionics App and Xantrex Inverter App battery voltages match at 100% battery full. However, the Xantrex voltage reading gets less accurate as the battery is used up. I had the Xantrex Low Voltage Cutoff set to 12.1v, but at 40% SOC battery I got an inverter low voltage shutdown. The Xantrex voltage was reading about 3 volts less than the Lithionics App battery voltage, so when the air conditioner compressor kicked on it blipped the voltage down to 12.1 for a second and that was enough to trigger the inverter low voltage shutdown. It immediately restarted but I don't want any interruptions like that when I'm using it, so I changed my Low Voltage Cutoff setting to 11.8v and didn't have anymore issues. For the way I plan on using my setup I really don't need an Inverter Low Voltage Cutoff but the Xantrex doesn't let you disable it, so I'll set it using my 3v difference and that should solve the problem but still give me a reasonably comparable, with the actual Lithionics voltage, Inverter Voltage Cutoff. Since the Lithionics shuts itself down at 12v (Never Die 10% reserve) it doesn't really matter what you set the Xantrex low voltage cut off as long as it's sufficiently low not to kick the inverter off when using the battery down. I don't know if the Victron Multiplus is better synchronized to the Lithionics voltage than my Xantrex, but that is something to watch in case you need to change your Victron Low Cutoff setting. These screen shots were taken at the same time (air conditioner compressor running) and see how off the Xantrex inverter readings are as compared to the Lithionics readings.
2. After I adjusted some of the Xantrex inverter settings, everything was smooth sailing. The air conditioner continued to run fine down to 21% SOC, when I switched back to shore power. I did notice that my AC thermostat setting needed to be lowered by 1 degree to give me the same level of cooling that I experience on shore power. I really don't know why this is because I had plenty of inverter power, 122vac before the air conditioner compressor kicks on and then stayed at 119v or higher, so very good power. Here are the amp draws, the fan draws 22-25a and when the compressor kicks on the draw jumps to 125a-155a.
3. Typically I experience pretty poor pedestal power at State Parks, consequently it doesn't support running the coach and recharging the battery at my inverter 50a Charger Current setting, so I had to reduce it to 20a to keep it above 114vac when the air conditioner runs. So keep this in mind because you may have to adjust that setting.
4. My Victron BMV-712 external battery monitor, doesn't stay synced with the true SOC of the Lithionics battery. The Victron runs a few percent less, even when you sync it to 100% often.
5. Even with the sun shining directly on my inverter compartment the Xantrex had no temperature issues. From the outside I could hear the cooling fans running, but inside I couldn't hear a thing. So the Xantrex operating isn't a disturbance at all!
Overall I'm very pleased with my results, in fact getting 4 hours of air conditioner run time exceeded my expectations!
I'm guessing in 95-100 degrees temperatures my AC run time could get cut in half, but I'll soon be testing it because in another month the SC temperatures will peak at that for the rest of the summer. I'll report again when I have results in those temperatures. Here are my new Xantrex inverter settings.
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