R23 AC/DC Fridge - Not on AC?

Greetings.

It seems that the last couple of times I got to my boat, kept in a slip and on shore power (yes the power is on), the fridge was warm but the light was on. After disconnecting shore power, turning on the house bank and using the boat the fridge gets cold.

I leave the fridge on 4.5 at all times. I thought that fridge was on all the time even without the house power turned on and automatically switches from AC to DC.

I'll try and get to/inspect the wiring near behind the fridge through the adjacent under-sink cabinet but is there something obvious I am overlooking or should check? The DC fuse is accessed behind the dash from the head and it looks good. Are there seperate AC and DC fuses?

Thanks.

RT23 Kingfisher said:

Greetings.

It seems that the last couple of times I got to my boat, kept in a slip and on shore power (yes the power is on), the fridge was warm but the light was on. After disconnecting shore power, turning on the house bank and using the boat the fridge gets cold.

I leave the fridge on 4.5 at all times. I thought that fridge was on all the time even without the house power turned on and automatically switches from AC to DC.

I'll try and get to/inspect the wiring near behind the fridge through the adjacent under-sink cabinet but is there something obvious I am overlooking or should check? The DC fuse is accessed behind the dash from the head and it looks good. Are there seperate AC and DC fuses?

Thanks.

Click to expand...

The fridge is 12volt DC only. When connected to shorepower, the battery charger provides power to the refer. Shut off the DC house switch and the refer loses power.

Thank you Martin. That would explain it and probably told to me by Fluid Motion but forgot. On the boat now and light IS NOT on when on shore power. I assumed it operated like a fridge I had in a camper (AC/DC) in a past life. Thanks again.

RT23 Kingfisher said:

Thank you Martin. That would explain it and probably told to me by Fluid Motion but forgot. On the boat now and light IS NOT on when on shore power. I assumed it operated like a fridge I had in a camper (AC/DC) in a past life. Thanks again.

Click to expand...

I asked the factory awhile back about this, as the question gets asked often. They do make a refrigerator module that works on AC and DC. The factory doesn't install those as they apparently draw more power on DC compared to the refrigerator module that only support DC is more energy efficient.

We leave our boat connected to shore power, battery charger on, and leave both our refrigerators running year round.

Submariner said:

I asked the factory awhile back about this, as the question gets asked often. They do make a refrigerator module that works on AC and DC. The factory doesn't install those as they apparently draw more power on DC compared to the refrigerator module that only support DC is more energy efficient.

We leave our boat connected to shore power, battery charger on, and leave both our refrigerators running year round.

Click to expand...

Just a question about that Martin. What is your feeling about keeping LIFEPO4 batteries at a 100% state of charge for extended periods when not in use? I have been going out of my way to try to keep mine between 50% and 70% charge in storage. It is surprisingly difficult, and I kind of want to just give up and leave them fully charged.

I typically only use the fridge when out on extended trips.

Having it endlessly cycle for a 2 hour outing can’t be healthy for the compressor. Also if you forget to shut off the house bank, the batteries will be dead within 48 hours - assuming no solar, or shore power. My fridge draws about 65 watts and once cool, cycles about 30 minutes per hour.

As a solution i wired the fridge to a separate fused toggle switch which i located behind the pilot seat, and which bypasses the main battery switch.

Another issue I had with the fridge is the fragility of the white liner. If you leave soda cans in the door or allow stuff to roll around in there, over time these surfaces will be destroyed. I now have plastic trays for everything in that goes in the fridge.

Keep cool all.

Thats interesting SeaCabin. I have 400 watts of solar and a smart shunt so I will monitor the fridge's power consumption during use while off grid.

RT23 Kingfisher said:

Thats interesting SeaCabin. I have 400 watts of solar and a smart shunt so I will monitor the fridge's power consumption during use while off grid.

Click to expand...

The cabin refer will use about 45amp-hours a day, more in the summer, less in the winter. When it's hot outsdie, the refer's consume a lot more power. The cockpit refer will consume about 25amp-hours a day. I've measured them using the battery monitor and solar controller, connected to a cerbogx with Internet connectivity to VRM, Victron's cloud portal.

If both refer's are running I'll be just over 100 watts... with one or the other running, I'll see between 50 and 70 watts... with neither running I'm at 27 watts, flat.
To measure the refer's, I would turn everything off at sunset, and let VRM monitor it through sunrise, and then average the consumption over time as the refer's turn on and off, cycling, throughout the day.

venajeff said:

Just a question about that Martin. What is your feeling about keeping LIFEPO4 batteries at a 100% state of charge for extended periods when not in use? I have been going out of my way to try to keep mine between 50% and 70% charge in storage. It is surprisingly difficult, and I kind of want to just give up and leave them fully charged.

Click to expand...

It’s totally fine to leave LiFePo4 batteries at 100% for a few days or so. It is also fine to charge to 100 regularly, unlike other lithium chemistries. However, if you are going to leave them for 5-6 months, they will last longer if keep them at 50-60%. However, unless you have a charger setup that holds that state of charge it’s not going to be easy to do that. I think most people would likely just leave them at 100% all the time. Lithium batteries last much longer than we originally thought based on what we are seeing in electric cars, so it probably won’t make very much of a difference on the whole. They are safe to leave at any state of charge.

Submariner said:

I asked the factory awhile back about this, as the question gets asked often. They do make a refrigerator module that works on AC and DC. The factory doesn't install those as they apparently draw more power on DC compared to the refrigerator module that only support DC is more energy efficient.

We leave our boat connected to shore power, battery charger on, and leave both our refrigerators running year round.

Click to expand...

Good to hear that DC is more efficient. My 2019 NovaKool was leaking refrigerant and I just replaced it with a similar 4500DC RF...I was able to reuse the stainless steel panel as it's an option on new fridges. I'd heard a lot about how these NovaKools can be repaired, but, speaking with a number of fridge dealers, they want nearly the full price of a new fridge to fix a leak and guarantee for much less time than a new model. I also got RF, handle on LHS, which is much better since it opens all the way. With the factory LF model, I constantly spilled defrost water in the boat since I couldn't open the door all the way...not good with my freezer that always had bait.

venajeff said:

Just a question about that Martin. What is your feeling about keeping LIFEPO4 batteries at a 100% state of charge for extended periods when not in use? I have been going out of my way to try to keep mine between 50% and 70% charge in storage. It is surprisingly difficult, and I kind of want to just give up and leave them fully charged.

Click to expand...

LFP prefers to live in a state of partial charge — anywhere above 20% but below 95%. That's the sweet spot for long-term health.

We boat year-round so true storage isn't really my reality, but I've thought through what I'd do if I laid the boat up for 3-4 months or longer. Discharge below 95%, isolate the bank completely, and the battery can sit comfortably for up to a year. Manufacturer specs say target 50% SOC for long-term storage — Lithionics published a good document on this and their takeaway was that the gains between storing at 50% vs 95% are minimal. Above 20% and below 95% is sufficient.

The bigger risk most people don't think about is leaving LFP on a battery charger continuously. That will reduce capacity over time, I've read up to 20% reduction with enough exposure. My Lithionics battery has two BMS aging counters that directly (negatively) affect warranty replacement value. One tracks heat exposure, close to zero for me since I run an outboard in the PNW. The other tracks Aging Factor SOC, which increments the longer the battery stays plugged into shore power near full charge. Getting it off the charger stops that counter.

Here's what I actually do when the boat sits for a month or two.
This is unique to my boat in how I redesigned the electrical system when I converted to LFP.

I run the inverter and boil water in the microwave until SOC drops below 95%. Then I trip my 250-amp house breaker which fully isolates the LFP bank (this is my T-Class fuse). I enable the parallel switch to join engine and house banks, disable charging in my Victron solar and OrionTR controllers via Bluetooth, and leave the 20-amp engine battery charger running on shore power. My 60 amp dedicated LFP battery charger powered off. The boat stays fully functional on 12V throughout the cabin, running off the engine battery, while the LFP bank sits isolated, not charging, not discharging.

I also push the physical on/off button on the Lithionics battery itself. My battery has a built-in thermal blanket that pulls up to 40 watts when temps drop below 40 degrees. If the battery is isolated but still powered on, that blanket will quietly drain it through cold nights. Button off eliminates that.

Once May gets here, I spend more time off shorepower than on it, and just let the 420 watts of solar and LFP cycle for weeks, months.

Four years in, my BMV shows 85 cycles. Average discharge is 160Ah out of 320. Deepest discharge was 254Ah. AGM gets 300-500 cycles. LFP is rated for 2,000+. I'm a long way from worrying about either number.

The inverter/microwave is obvious now that you say it. I use the hot water heater when I have water in the tank but when it is empty I have to play the leave lights on for x amount of time game. To be honest I often forget I have a microwave onboard. I will start using that method.