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1975 Newport 28
1986 Hunter 31
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602 Posts
Discussion Starter · #1 ·
My Hunter 31 has a built-in Adler Barbour fridge that works just fine. It's 12v, which makes me wonder how it's supposed to be used. Surely the power drain is too high to use it without being plugged in at a slip. Can it be used under battery power without draining them dead?
 

bell ringer
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Been running my frig and freezer off the battery for 10.5 years. Even right now I am plugged into shore power, but the battery charger is off and all DC loads are running off the batteries and solar.

but no way to answer your question without knowing the battery capacity and what you are doing for charging.
 

Dirt Free
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Short answer, yes your batteries will run down at some point if not on shore power.
Real answer, needs a lot more info as Don L said.
 
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Hard to generalize but most of these small reefer unit will draw about 5 amps when running and will cycle on and off when the box is down to temp. Maybe need somewhere in the vicinity of 50 to 70 AH daily. So that will pull a typical 12V grp 24/27/31 battery to at or below 50% in a day. So you will need a decent sized house battery bank and either solar or a wind generator if not plugged in. Just running the engine for an hour or two will help, but never get back to near 100% charge.
 

1975 Newport 28
1986 Hunter 31
Joined
602 Posts
Discussion Starter · #5 ·
Been running my frig and freezer off the battery for 10.5 years. Even right now I am plugged into shore power, but the battery charger is off and all DC loads are running off the batteries and solar.

but no way to answer your question without knowing the battery capacity and what you are doing for charging.
Fair enough. I'll have to go look and see what batteries I have. All I know offhand is that they're Group 24 West Marine batteries. I'm on shore power most of the time. I'm on Rock Creek on the south shore of the Petapsco River, just off Chesapeake Bay. I've got no plans for any long passages, so I'll be doing mostly day sailing. I'd like to do some overnights down the Bay, at night either on the hook or at a slip somewhere.
 

bell ringer
Joined
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Fair enough. I'll have to go look and see what batteries I have. All I know offhand is that they're Group 24 West Marine batteries. I'm on shore power most of the time. I'm on Rock Creek on the south shore of the Petapsco River, just off Chesapeake Bay. I've got no plans for any long passages, so I'll be doing mostly day sailing. I'd like to do some overnights down the Bay, at night either on the hook or at a slip somewhere.
Well then the answer is yes you can run your refrigerator. When at a dock with shore power your battery charger powers it. When not your batteries will and you will need to run engine as needed to recharge before you discharge them too low.
 

1975 Newport 28
1986 Hunter 31
Joined
602 Posts
Discussion Starter · #7 ·
you will need to run engine as needed to recharge before you discharge them too low.
And there's the crux of the biscuit, as Frank Zappa once said. How often would I need to run the engine? Would it be a good strategy to switch to battery 2 only for the fridge while day sailing?

Surely, somewhere on the fridge compressor, or somewhere, is the power requirement. And on my batteries, their storage capacity, and the output of my generator/alternator. All that info should let me calculate my power usage.
 

Master Mariner
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It is all just simple math. If your fridge operates at 3 amps an hour, and you have 300 amps of battery power, you will need to charge every 100 hours. Solar helps, but unless you have a pretty decent array, you may not keep up with the consumption. As I said, simple math.
 

bell ringer
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someone needs to do some reading up because there isn't any reason to reinvert this wheel
 

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And there's the crux of the biscuit, as Frank Zappa once said. How often would I need to run the engine? Would it be a good strategy to switch to battery 2 only for the fridge while day sailing?

Surely, somewhere on the fridge compressor, or somewhere, is the power requirement. And on my batteries, their storage capacity, and the output of my generator/alternator. All that info should let me calculate my power usage.
It is not as simple as just reading the nameplate and making a quick calculation. You need to measure the actual amp draw of the compressor and multiply that by the duty cycle which is how how long it runs each hour. Even that is just a rough estimate of your power consumption over a period of days.

The short answer is, if you are only running 1 group 31 battery you will might be good for a day, but not much more, and that is assuming your battery is in perfect condition.

To give you an example, my fridge consumes around 40ah overnight. A typical group 31 battery is rated for around 110ah, but most lead acid batteries can only be drawn down to 50% without damaging them, so you only have 55ah to work with at best.

If you want to be off grid for longer periods of time you will need to upgrade your battery bank or your charging sources, ideally both.

Sent from my SM-G981W using Tapatalk
 

Dirt Free
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Except if
It is all just simple math. If your fridge operates at 3 amps an hour, and you have 300 amps of battery power, you will need to charge every 100 hours. Solar helps, but unless you have a pretty decent array, you may not keep up with the consumption. As I said, simple math.
Except if you take300amps of a 300amp/hour battery ... it's dead and will likely never likely recover.
 

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Fair enough. I'll have to go look and see what batteries I have. All I know offhand is that they're Group 24 West Marine batteries. I'm on shore power most of the time. I'm on Rock Creek on the south shore of the Petapsco River, just off Chesapeake Bay. I've got no plans for any long passages, so I'll be doing mostly day sailing. I'd like to do some overnights down the Bay, at night either on the hook or at a slip somewhere.
Even assuming these are "deep cycle" batteries (not likely), this is totally inadequate to power a refrigeration system at anchor for any length of time. Until you plan on longer cruises, just use block ice for the occasional overnight and use the reefer when plugged in at a slip or when running the engine and charging the batteries.
 

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Time to start reading up on marine battery systems. Your batteries are not true deep cycle batteries and with about 70 amp hour capacity and the fact that you can only use 50% of the capacity before you will be damaging the batteries you have about 35 amp hours per battery, so then the simple math and it is not really that simple you can run your frig for about 7 hours on a hot day for each battery.
 

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Moody 376
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Sorry to jump in here, not trying to derail or hijack the thread.

but is there device to measure how much juice a specific instrument uses over a period of time. IE could I wire up a bilge pump counter or an hour meter to it such that each time the unit cycles on and off I can figure out my usage?

if a refer used 3ah, thats great, but we know that its generally not running continuously it is cycling on and off. so its actual consumption over the course of 24 hours isn't likely 3 ah..Right?

in my situation, Ive got two banks set up and each bank is 2 6v gc2 bats (capacity 215AH 110 min reserve cap @ 75 amps) wired in series to get my 12v.

in theory, if my refer drew 3ah continuously.
i could run for 71 hours and kill one bank beyond recovery. or 35 hours to only use 1/2 of my available capacity. or 57 hours if I'm feeling lucky and want to go down to 80% cap Right? assuming no other loads on the battery...
 

Dirt Free
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Sorry to jump in here, not trying to derail or hijack the thread.

but is there device to measure how much juice a specific instrument uses over a period of time. IE could I wire up a bilge pump counter or an hour meter to it such that each time the unit cycles on and off I can figure out my usage?

if a refer used 3ah, thats great, but we know that its generally not running continuously it is cycling on and off. so its actual consumption over the course of 24 hours isn't likely 3 ah..Right?

in my situation, Ive got two banks set up and each bank is 2 6v gc2 bats (capacity 215AH 110 min reserve cap @ 75 amps) wired in series to get my 12v.

in theory, if my refer drew 3ah continuously.
i could run for 71 hours and kill one bank beyond recovery. or 35 hours to only use 1/2 of my available capacity. or 57 hours if I'm feeling lucky and want to go down to 80% cap Right? assuming no other loads on the battery...
Google "Battery monitor"
 

One of None
Hunter 34
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you're 12 volt refrigeration system won't kill your batteries unless you want it to, they are very very low horsepower can't even measure it in horsepower so it's measured in amps or Watt hours. The refrigeration effect is very small which is why they're usually applied to very small boxes.


Basically, All 12/24 volt refrigeration systems are a modern miracle which came along inearly or mid 80s!

Just for fun I ran my new unit on a single battery for 2 days and the battery was still able to start the engine of the boat,

Most 12/24 volt refrigeration only draws less than five amps (you figure out your amp hours because everybody's boat is different).

Nobody does it of course unless they're full-time on their boat but, once the box is cold, it tends to stay cold with less energy then it takes to run the system from a "hot" start.
 

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My Hunter 31 has a built-in Adler Barbour fridge that works just fine. It's 12v, which makes me wonder how it's supposed to be used. Surely the power drain is too high to use it without being plugged in at a slip. Can it be used under battery power without draining them dead?
Well, there are calculations and formulas for that... But if you are as lazy as I am, just turn off your shore power for three days. If the batteries are dead, replace them. Boat refrigeration is generally speaking amazingly efficient. You should be able to unplug for 3 days easy...
 

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Well, there are calculations and formulas for that... But if you are as lazy as I am, just turn off your shore power for three days. If the batteries are dead, replace them. Boat refrigeration is generally speaking amazingly efficient. You should be able to unplug for 3 days easy...
On one group 27 battery? Not a chance!

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Dirt Free
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you're 12 volt refrigeration system won't kill your batteries unless you want it to, they are very very low horsepower can't even measure it in horsepower so it's measured in amps or Watt hours. The refrigeration effect is very small which is why they're usually applied to very small boxes.


Basically, All 12/24 volt refrigeration systems are a modern miracle which came along inearly or mid 80s!

Just for fun I ran my new unit on a single battery for 2 days and the battery was still able to start the engine of the boat,

Most 12/24 volt refrigeration only draws less than five amps (you figure out your amp hours because everybody's boat is different).

Nobody does it of course unless they're full-time on their boat but, once the box is cold, it tends to stay cold with less energy then it takes to run the system from a "hot" start.
I think you missed a few things Denise. The OP knows nothing about amps vs. amp hours, voltage, how to measure the the condition of his batteries or even the conditioo or type of his batteries or whatever else he runs on 12 volts. I believe he also said he has 2" of crumbling old insulation.
I believe you are being a little optimistic.
 
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