cabin refrigerator


rpm605

rpm605

Member
the the last 2 times we spent the night on the hook, I've noticed that the cabin refrigerator freezer begins to thaw out after about 6 hours on the house battery. Is this typical? if I fire up the generator it goes right back to normal. It's a dual voltage refrigerator. Refrigerator is only 2 years old and works great off the generator and Shore power. House battery was brand new going into this year. Outside ambient temperatures were in the low 80s.
 
Sounds perfectly normal. House battery only lasts about 4 hours with the fridge running. If you're getting 6 you're doing good.



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Hmmmm ... not sure on this one ... according to my refrigerator owner manual, it looks like mine has an instantaneous maximum draw of 6 amps (at 12 volts) and an average consumption over 24 hours of about 400Watt-hours. That calcs to an nominal current draw over a 24 hour period of around 1.5-2 amps. Given that my (upgraded) house battery (a Northstar AGM battery) has a 100amp-hour discharge capacity, if I limit my discharge to 50% and pull no other power, my battery should be able to handle my refrigerator for 24 hours.

I also note that the refrigerator monitors battery voltage coming to it, and shuts down when the voltage is too low (both to protect the compressor and to keep from draining the battery to zero.

If you're only getting 4-6 hours from your house battery before your refrigerator drops off, you might want to check both your house battery's charge state and how many other loads you have running when you are at hook. Since you have a new battery, it shouldn't be sulfated yet (hence able to hold a full charge), but remember that battery life is a function of their average level of charge and you can kill a new battery fairly quickly if you don't bring it back to full charge regularly. Take a look at your battery charger and the "full up" charge level of the battery to see if you are actually charging your battery to 100%.

Incidentally, after talking to Northstar tech reps, we concluded that the OEM Charles Charger on the boat wasn't able to adequately bring/keep their AGM battery at proper charge levels, so I changed out my charger as a part of upgrading my batteries to AGM type.
 
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Everyone I talk to gets about 4 - 6 , not doubting your theory rclementtx but sometimes theory doesn't line up with reality. Also, in my experience the energy ratings manufacturer's give are under optimal conditions in a lab. Are you getting 24 hours run time on your 310?

Also, I failed to mention that I have two fridges running that drain the single house battery in 4 hours, I assume rmp605 is running both his or at least the much larger salon refrigerator/freezer in his 37PC.
 
afratki said:
... not doubting your theory rclementtx but sometimes theory doesn't line up with reality ...
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The engineer in me forces me back to my calcs, which served me well in my career. But I'll defer to your guys experience ... different boats, different batteries, different usage (overnight vs. day), different house loads when on the hook, etc. Plus 2x refrigerators immediately translates to 2x the nominal current draw on that part of the equation.

Over the past few years I've become a real student of batteries and battery life. Thats what aimed me to AGM batteries when I replaced my dead house battery on my recently acquired 310SS. My unstated theme in my earlier post pertains to taking care of your house batteries by keeping them 100% topped up when not in use. If you want to learn more on the whole subject try this site ... http://batteryuniversity.com.

Victron makes a reasonably cost effective (~$200) battery monitor that might play a role here in monitoring your draw on your house batteries if your 4-6 hour lifetime is a problem. I've read reviews where its been installed on boats plus RVs. I haven't splurged yet on one of these, but they are a rather nice way to know the status of your house battery before it simply doesn't run your refrigerators. And as an FYI, Formula has recently changed over to Victron chargers on the newer boats since their old standby Charles Chargers are no longer made for marine use. You can find more at ...

http://www.truckcamperadventure.com...and-mppt-controller-with-smart-phone-display/

https://www.amazon.com/Victron-Batt...=8-6&keywords=victron+bmv-712+battery+monitor
 
rclementtx said:
Hmmmm ... not sure on this one ... according to my refrigerator owner manual, it looks like mine has an instantaneous maximum draw of 6 amps (at 12 volts) and an average consumption over 24 hours of about 400Watt-hours. That calcs to an nominal current draw over a 24 hour period of around 1.5-2 amps. Given that my (upgraded) house battery (a Northstar AGM battery) has a 100amp-hour discharge capacity, if I limit my discharge to 50% and pull no other power, my battery should be able to handle my refrigerator for 24 hours.

I also note that the refrigerator monitors battery voltage coming to it, and shuts down when the voltage is too low (both to protect the compressor and to keep from draining the battery to zero.

If you're only getting 4-6 hours from your house battery before your refrigerator drops off, you might want to check both your house battery's charge state and how many other loads you have running when you are at hook. Since you have a new battery, it shouldn't be sulfated yet (hence able to hold a full charge), but remember that battery life is a function of their average level of charge and you can kill a new battery fairly quickly if you don't bring it back to full charge regularly. Take a look at your battery charger and the "full up" charge level of the battery to see if you are actually charging your battery to 100%.

Incidentally, after talking to Northstar tech reps, we concluded that the OEM Charles Charger on the boat wasn't able to adequately bring/keep their AGM battery at proper charge levels, so I changed out my charger as a part of upgrading my batteries to AGM type.
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I'll be curious to see if the OEM Charles charger on my boat adversely affects the life of the Intimidator AGM batteries that came with my boat. Second year and no problems yet. I can confirm, like you that I can run 1 refrigerator for at least 24 hours. I do have 2 house batteries though. I would imagine I could probably go more than 24 hours, but have not tried that as yet.
 
Using a Norcold DE0041 ref/freezer. small 3.6 cu ft. My house battery is wired in series with my port starting battery. Took over an hour of cruising and hour on shore power for the the charging level to come back up to normal on the house/port starter battery. the only other 12v items that we ran overnight were the anchor light and 2 phone chargers.
 
Jshell said:
I'll be curious to see if the OEM Charles charger on my boat adversely affects the life of the Intimidator AGM batteries that came with my boat.
Click to expand...

When I decided on the Northstar AGMs (both house and starting), I called Northstar tech reps to talk about preferred charging profile for their batteries since I pretty much concluded that they were one of the top 2 AGM brands in the marketplace. After opening up my Charles Charger I found it didn't have switchable profile and that the voltages were too low to get full charge on the Northstar AGMs. Northstar recommends 3 step charge profile - Bulk Charge at 14.6-14.8 volts / followed by Adsorption at 14.2-14.6 volts / followed by Float at 13.6-13.8 volts. They strongly recommended the Dual Pro PS2 as their charger of choice. It is temperature compensated plus its charge voltages are right "there" in terms of Northstar's recommendations. Checking voltage readings during charge and float stages validates this as well.

If you are concerned about your Intimidator AGMs, give the manufacturer a call and compare what the Charles Charger manual indicates for your boat. As long as you don't over charge the Intimidators with the Charles, you won't "kill 'em". But consistently undercharging them will shorten their potential life (which with good AGMs could be 5+ years - much better than lead acid batteries).

By the way, changing out the Charles Charger with a Dual Pro was more complicated then I originally envisioned given that Formula wires the boat to send the charge current to circuit breakers in the aft breaker panel and then to the adjacent battery parallel switch before ending up at the battery. I had to make a decision on whether I kept the Dual Pro temperature regulation (which is important for AGM batteries) or the Formula circuit breaker protection. I ended up voting for the temperature regulation (since the charger had internal circuit protection) which caused me a bit of rewiring in cramped spaces (actually abandoning the 2 Charles Charger output cables in place after putting them in a box and isolating them electrically). And perhaps the most fun was rigging the 75# AGMs back onto their mounting trays!
 
rpm605 said:
Using a Norcold DE0041 ref/freezer. small 3.6 cu ft. ...
Click to expand...

Hey rpm605 ... My refrigerator is an Isotherm unit. Not sure how different they are (if at all), but the 1.5 - 2 amp current draws that I mentioned earlier were for Isotherm units.

Taking a few hours to get your battery back to some semblance of charge doesn't sound out of whack, especially if the battery was deeply discharged.

Your charger is probably putting out 40-50amps and a 50% discharged battery means you probably have to replace ~40-50amp-hours of energy. That means it would take 1-2 hours depending on the charge profile, assuming all of your charge current was going into the battery (and not other electronics on the boat).

The unknowns here are the state of charge on your battery when you shut down your generators.
 
rclementtx said:
When I decided on the Northstar AGMs (both house and starting), I called Northstar tech reps to talk about preferred charging profile for their batteries since I pretty much concluded that they were one of the top 2 AGM brands in the marketplace. After opening up my Charles Charger I found it didn't have switchable profile and that the voltages were too low to get full charge on the Northstar AGMs. Northstar recommends 3 step charge profile - Bulk Charge at 14.6-14.8 volts / followed by Adsorption at 14.2-14.6 volts / followed by Float at 13.6-13.8 volts. They strongly recommended the Dual Pro PS2 as their charger of choice. It is temperature compensated plus its charge voltages are right "there" in terms of Northstar's recommendations. Checking voltage readings during charge and float stages validates this as well.

If you are concerned about your Intimidator AGMs, give the manufacturer a call and compare what the Charles Charger manual indicates for your boat. As long as you don't over charge the Intimidators with the Charles, you won't "kill 'em". But consistently undercharging them will shorten their potential life (which with good AGMs could be 5+ years - much better than lead acid batteries).

By the way, changing out the Charles Charger with a Dual Pro was more complicated then I originally envisioned given that Formula wires the boat to send the charge current to circuit breakers in the aft breaker panel and then to the adjacent battery parallel switch before ending up at the battery. I had to make a decision on whether I kept the Dual Pro temperature regulation (which is important for AGM batteries) or the Formula circuit breaker protection. I ended up voting for the temperature regulation (since the charger had internal circuit protection) which caused me a bit of rewiring in cramped spaces (actually abandoning the 2 Charles Charger output cables in place after putting them in a box and isolating them electrically). And perhaps the most fun was rigging the 75# AGMs back onto their mounting trays!
Click to expand...

Seems to be charging ok, so I'm not going to borrow trouble.
 
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