Fridge won't run on DC anymore, will this work as a stop-gap?

Island Time Buffalo

Active Member
Aug 19, 2014
240
Grand Island, NY
Boat Info
380 Sundancer 1999.
Engines
7.4 Horizons
Hi all. 1999 380DA, original fridge, so it's prolly on its way out. Will run on shore power, but not battery. The power light will go on, but it won't fire up the compressor. Battery bank is new, plenty of voltage available.

And for those not familiar, getting to anything behind that fridge is a monumental task requiring disassembly of the cabinetry.

I'm trying to hold out another year before I take on the task/cost of replacing it.

So if there isn't a quick thing to check/fix, I have an idea to get me through a weekend trip where we'll be off-power for several hours travelling.

I'm thinking of grabbing a 1500 watt inverter and another battery, and plugging my shore power cord into it (with only the fridge circuit open). I'm not trying to solve the bigger problem, just the immediate one ...... trying to keep the food cold for a few hours of travel this weekend.

Would it work?
 
Your fridge/freezer should be fine for a few hours without power if you leave it closed. They may be old but they're still decent units. If you're worried, toss a couple frozen gallons of water in your fridge before you depart. Better yet, just use coolers :)

I wouldn't waste the time and effort of adding batteries and an inverter for what you're trying to do. My two cents only of course.
 
What make/model of fridge is it?

1500 watt is probably HUGE overkill, but that should work. I'd bet the draw is more like 200 watts, so if you oversize for a start-up surge, you're still WELL below 1500w. Some of the older Norcolds only had a 60W compressor.

But yes, that would work.

I'd often thought about putting a voltage-sensing relay between the shore power charger and things like a fridge on the 12V line, with a time-delay so that the fridge would only run for a few hours if the voltage dropped to 12.6 (or lower) so you'd NEVER run the battery down substantially so the battery would still be OK enough for the bilge pump(s). Would still run the fridge fine as long as the batteries were getting charged (like, while underway), or for several hours out at the sandbar.
 
What make/model of fridge is it?

1500 watt is probably HUGE overkill, but that should work. I'd bet the draw is more like 200 watts, so if you oversize for a start-up surge, you're still WELL below 1500w. Some of the older Norcolds only had a 60W compressor.


Good point, I just checked. It's a Norcold, and it looks like its .7 amps and 120 volts, which if my maths work, that makes it 84 watts. Not sure what the startup surge would be though .... maybe 2X ???
 
Your fridge/freezer should be fine for a few hours without power if you leave it closed.

Sadly, that's how we discovered the issue, at anchor for a few hours and the freezer started defrosting into the fridge and made a mess. I was surprised it didn't hold the temp better than it did.
 
Sadly, that's how we discovered the issue, at anchor for a few hours and the freezer started defrosting into the fridge and made a mess. I was surprised it didn't hold the temp better than it did.

Dang. That does stink. Have you tried to clean up the seals? Is it closing tight?
 
Well, the proof-of-concept works great. I didn't risk putting the inverter on the existing battery bank and cause some kind of loop and short everything out, so I have a small 12vt tractor battery on the inverter and ONLY the fridge turned on. It works perfectly. Now we'll see how much battery life there is on this experiment.... by all calculations I should have several hours of life. ..... we shall see. Wish me luck LOL.
 
A typical small tractor battery might be 20AH. At around a 10A load, that'd give about 2 hours MAX until it's dead. If the fridge is running 50% of the time (depends on outside temp), that might get you to 4 hours but it also would result in a completely dead battery that would take a while to charge back to 100%.

One thing you can do to extend the battery life is put the fridge on the COLDEST setting for a few hours while you're still on A.C. power, then turn it back to "normal" when you're going to be on battery. Also helps if you stuff a couple of those "blue ice" things in the freezer to get them solid, then move them to the fridge when you go on battery.

Good luck!
 
A typical small tractor battery might be 20AH. At around a 10A load, that'd give about 2 hours MAX until it's dead. If the fridge is running 50% of the time (depends on outside temp), that might get you to 4 hours but it also would result in a completely dead battery that would take a while to charge back to 100%.

One thing you can do to extend the battery life is put the fridge on the COLDEST setting for a few hours while you're still on A.C. power, then turn it back to "normal" when you're going to be on battery. Also helps if you stuff a couple of those "blue ice" things in the freezer to get them solid, then move them to the fridge when you go on battery.

Good luck!

Got 3.5 hours off a $20 battery. The inverter shuts itself down at a certain low voltage, so it didn't destroy the battery and it charged fine. So with doing the above steps you indicated, it got us through 4 days of travel up the Erie Canal. We had a couple 8-hour travel days, and setting the 3.5 hours in the middle of the run worked with no issues and no appreciable loss of fridge temp - frozen stayed frozen, and cold stayed cold.

Kludgy as hell, but it worked for my immediate need. I don't have any more extended runs planned this year, so ..... New fridge next year ... yay me!!!

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From a post back in Aug 2021,

After replacing that AC/DC control module box, which is nothing more than a step down transformer, it lasting 1 year and a week. About 7 years ago I by-pasted that box and connected the battery wires to the frig. These refrigerators need 12 volts. The box just steps down the power from 120v to 12v. Did my freezer about 5 years ago and both running strong. I don't run them when the boat is behind the house here, but if we are loading up days before a trip, then during then trip and when we are unloading the frig & freezer are running this way. Batteries are always being charged. so there is no problem with power at all.

Just my $.02!

D
 
Maybe I missed someone else saying this but…. Just start up the gen?

I neglected to include that piece of info. The Genny is also in the shitz. Typical Westerbeke nonsense (I've spent more money and time on that piece of garbage than I care to admit). I've got a guy lined up for that project too as I've exhausted all my skills on it. But that also may end up as a next year project.
 
From a post back in Aug 2021,

After replacing that AC/DC control module box, which is nothing more than a step down transformer, it lasting 1 year and a week. About 7 years ago I by-pasted that box and connected the battery wires to the frig. These refrigerators need 12 volts. The box just steps down the power from 120v to 12v. Did my freezer about 5 years ago and both running strong. I don't run them when the boat is behind the house here, but if we are loading up days before a trip, then during then trip and when we are unloading the frig & freezer are running this way. Batteries are always being charged. so there is no problem with power at all.

Just my $.02!

D

That's actually how the cockpit fridge runs. Pure DC.
 
ITB,
I missed where you said the make and model of the probelm child?
 

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