Refrigerator and loss of shore power

[RNC725]

We have a 2002 Hunter 326 and we'll be adding refrigeration to her this fall. Every so often we will have a temporary power outage due to a downed tree or limb on our access road to the Sailing Club. I'm assuming if we lose AC power the unit will switch back to DC automatically. Then I started thinking what what if we lose power for more than a day or two which has happened we have really bad weather due to a tropical storm or hurricane. I suppose the best thing to do would be to run to the marina and turn off all power so my batteries would not be drained. Just curious if anyone else has this issue. I'm not too worried about a short-term loss of power as the batteries would be easy to compensate for that. I realize I'm probably over-analyzing mess. Even though we have access at no cost to our ice machine that are sailing club we are very much looking forward 2 refrigeration. Will add an additional deep cycle battery which will give us two house batteries and one cranking battery. Thanks everyone.

Fairwinds

 

[Stu Jackson]

You'll only lose what's in the fridge. Avoid mayo and meat and you might be OK.

Unless you have an energy budget you won't know how long the DC will last.

Unless you're a marina hopper, if you plan on anchoring out with a fridge, most of us recommend a minimum of 400 ah in the house bank. Usually daily load is 100 ah, so you get two nights on the hook (without solar and/or running the engine or a generator).

 

[RNC725]

Thanks for the advice and your points are well taken. I'm ordering a battery monitor this week so I can get an accurate count of amp hours on each piece of equipment that has any type of draw at all. We certainly have room for a fourth deep cycle if needed. I'm also looking into our solar panel or two as living in Georgia gives ample opportunity to slurp in some serious rays. The plan is to install the refrigerator sometime in late October or early November so we have plenty of time to make a plan, adjust the plan and finalize the plan. Again, many thanks.

 

[Don S/V ILLusion]

Among the solutions to protect your batteries from draining are a number of low voltage cutoff circuits and relays which can be set to shut down any loads at a pre-selected voltage. It’s a small investment particularly if you have lots of batteries to ensure you don’t kill them prematurely.

 

[RoyS]

I have one group 31 battery for house bank one and two golf cart batteries for house bank two. When I leave the boat plugged in on shore power I use the single group 31 battery for the fridge. Should the shore power be lost only one battery will be discharged and possibly damaged. You do not want to chance discharging a large bank and leaving it that way until you return and discover it. Limit your losses.

 

[JRT]

I have 4 golf cart batteries for our house load for 416 ah. My fridge is factory and runs on DC, when I leave the boat I leave it and my bilge pump on for DC load and connect shore power and charging. So far this has been fine with up to 3 days of disconnected shore power. I'd like to learn what low voltage cutoff circuits to install if there is a recommendation.

 

[Hayden Watson]

My fridge has a low voltage cutoff to protect the batteries when I loose shore power but that does not protect me from spoiled food. When I keep perishables in the fridge, I also keep a baggy of ice cubs in the freezer compartment. If the cubes loose their shape, I know I need to replace my perishables.

 

[JRT]

Interesting, I'll have to read my manual tonight again to see if that is true with mine.

 

[Hunter Ad Bot]

And now a word from the sponsor...

Cabinet catch for many Hunters

These catches were common on Hunters from the Legend-era through today's Marlow-Hunters. We keep a large stock on hand for emergency shipments or just getting spares.
See the product

 

[jviss]

If it's a Danfoss compressor and control unit, the default low voltage cut-out for a 12V system is 10.7V, cut-in at 11.7V. It's programmable, in almost 0.1V increments from 9.6 to 11.3 (it skips some) by installing a resistor between the C and P terminals.

https://www.hvacusa.com/media/datasheetfiles/101N0210.pdf

 

[Capt jgw]

My fridge has a low voltage cutoff to protect the batteries when I loose shore power but that does not protect me from spoiled food. When I keep perishables in the fridge, I also keep a baggy of ice cubs in the freezer compartment. If the cubes loose their shape, I know I need to replace my perishables.

That's a great idea!

 

[Maine Sail]

If it's a Danfoss compressor and control unit, the default low voltage cut-out for a 12V system is 10.7V, cut-in at 11.7V. It's programmable, in almost 0.1V increments from 9.6 to 11.3 (it skips some) by installing a resistor between the C and P terminals.

https://www.hvacusa.com/media/datasheetfiles/101N0210.pdf

Just be aware that these voltages are on the rather low side for battery discharge protection. The factory configuration of a 10.4V cut off point is actually below the 0% SoC threshold. If the power is off for any considerable amount of time, the batteries can be irreversibly damaged. If left unchanged from the factory configuration a smart charger may not re-boot automatically sensing too low a voltage for a safe re-boot when power comes back on.

For about $75.00 one can install an LVD such as the Blue Sea m-LVD. These are factory set to disconnect at 12.1V which is still approx 50% SoC, but not low enough to not allow a smart charger to re-boot.

 

[RNC725]

Wow, great ideas all! Am learning how much I've yet to learn...