Quote:
Originally Posted by Chance
With propane fridge running on inverter, “IF” it uses 300 Watts (and that’s in right ballpark), electrical current from battery will be even greater because of inverter not being 100% efficient. In total, batteries would need to supply about 30 Amps or more in order to make 300 Watts of heat at refrigerator.
The 2.5 amps came from Norcold and the 300 watts is on back of fridge when looking at plug.
More importantly, your batteries may be rated at 65 Amp-hours each, for total of 130 Ah, but that applies only to a very slow discharge rate over 20 hours. That works out to 6.5 Amps for 20 hours. When you discharge lead-acid batteries much faster than that, like at 30 Amps instead of 6.5 Amps, you will NOT get 130 Ah. It will be much less.
This would explain the why  My controlled experiment confirms. Today, with outside temperatures 75 degrees, I ran my inside Norcold for 1 hour and 30 minutes off my inverter. Batteries were fully charged at 13.7vdc when I started, the auto genset came on when battery voltage dropped to 12.1 vdc for a duration of at least 15 secs. There was no other load on the batteries
As I stated previously, running absorption fridge from batteries is not very efficient because of all these factors combined. I would only do it if driving with alternator powering the inverter, and stopped for gas or bathroom break for a few minutes, in which case I would let batteries power the fridge for a short period. If stopping for more than a few minutes, I’d go back to propane.
This is exactly my plan 
As to your outside kitchen fridge running much longer on batteries, it’s not only due to the lower power requirement, but also because it cools with a compressor which means that once temperature is reached, it cycles on and off as needed. Through the night on battery power, the fridge compressor may have only run a couple of hours depending on outside temperature. By comparison, propane fridge barely stay cold enough when running on electricity, so it’s likely it will draw closer to maximum current all night long.
Point duly noted. However one thing I read a lot but do not agree with is the coldness of our Norcold propane model. Maybe it is still new and will level off year 3 - 5? But our model has 5 frost flakes for setting. When I put on 4 Flakes we get ice in the bottled water and beer is freezing cold. We normally have at 3 Flakes unless we are traveling, then we set to 4 or maybe even 5 flakes if we know the fridge will have to be turned off for a while because I don't want to run generator or use propane. Our ice that we put in the freezer section has yet to melt even when we turn it off for 5 - 6 hours or so. |
Based on my findings and learnings, I will proceed to add an additional 110vac receptacle supplied by my inverter in my Norcold Fridge vent area. At first I was thinking I may switch back and forth by unplugging for trips but based on what I learned today, there is no need to.
I will leave plugged into inverter 100% of the time. However I will only use the Inverter power for the Norcold when driving or for a duration NOT to exceed 60 minutes. I will simply use my Norcold mode switch to turn on / off from the inverter. i.e. If I wish to use my Inverter for TVs or outside fridge ONLY... all I have to do is change the inside Norcold mode to Propane, or simply turn the Norcold off.
This is a win win for us as I will always have my Norcold Fridge and Inverter on when traveling. The outside fridge is usually off unless we need extra capacity but that has not occurred yet.
It will require some training with my wife. But it should be simple to look for that green inverter on button and verify the Norcold is set for Electric only. That way no chance for propane to come on while driving
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