3000 watt inverter Large AMP Draw problem 2017 Bighorn 3575EL

Short-Bed-Dually

Active Member
2017 Bighorn 3575EL
I have a 3000 watt inverter, six golf cart 6 volt batteries (1,290 AMP Hours), Go Power TS-50 automatic transfer switch, Functional Devices RIB2401B Power Relay and a AiLi battery monitor.The RIB2401B Relay is wired normally closed to power off the 80 amp converter when running on the inverter. The camper has the Norcold 2118SST refrigerator.
The problem I have is with the refrigerator on the inverter AC power the batteries are drawn down to 1/2 capacity in 6 to 7 hours. I attached the electrical test readings I have done. The readings at the AiLi battery monitor don't agree with the reading at the battery or the refrigerator plug. The fact that it draws down the batteries in this short of time agrees with the monitor. Any insight on this will be appreciated.
 

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danemayer

Well-known member
The Norcold 2118, on 120V AC power, runs about 600 watts, or 5 amps. Coming through the inverter, that would draw about 50 amps of 12V DC. So 50 amps of battery power when it's actually cooling. Depending on 1) how hot and humid it is at your location, and 2) how well the refrigerator is operating, in a 24 hour period, the runtime might be 12 hours. 12 hours at 50 amps would be 600 amp hours.

I'm guessing your figure on 1290 amp hours from your 6 volt batteries is derived from each battery having a 215 AH rating. But I think when you wire 2 in series to get 12V, you have 215 AH for the pair, not 430. So your total AH may be 645, not 1290.

So, if you actually have 645 AH, and your refrigerator is running for 12 hours out of 24, you will run the batteries down.

Have you considered running the refrigerator in 12V/propane mode?
 

Short-Bed-Dually

Active Member
The Norcold 2118, on 120V AC power, runs about 600 watts, or 5 amps. Coming through the inverter, that would draw about 50 amps of 12V DC. So 50 amps of battery power when it's actually cooling. Depending on 1) how hot and humid it is at your location, and 2) how well the refrigerator is operating, in a 24 hour period, the runtime might be 12 hours. 12 hours at 50 amps would be 600 amp hours.

I'm guessing your figure on 1290 amp hours from your 6 volt batteries is derived from each battery having a 215 AH rating. But I think when you wire 2 in series to get 12V, you have 215 AH for the pair, not 430. So your total AH may be 645, not 1290.

So, if you actually have 645 AH, and your refrigerator is running for 12 hours out of 24, you will run the batteries down.

Have you considered running the refrigerator in 12V/propane mode?

Dan,
Thank you for your quick reply.
You are correct on the batteries Amp Hour, I wasn't thinking about that when I wrote the post. I have the AiLi monitor set on 320 Amps which is close to 50% of the 645 Amp Hour capacity. I of course don't want to run the batteries down more than 50%. So my figures do make sense, sometimes it's hard to see the forest for the trees. I have been running the Norcold on propane so I don't use up the battery power when traveling. We haven't dry camped with this set up yet so I'll be using the propane then also.
 
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