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Old 07-12-2017, 12:16   #16
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

For 10 years I had a 120~V fridge on my boat I made by stripping off the box of a discarded dorm size fridge, twisting the condenser and evaporator carefully around until I was able to insinuate the evaporator and thermostat into the icebox (through a hole in the bulkhead), mount the condenser on said bulkhead and the compressor on a little shelf. It worked beautifully. I never made any attempt to feed it through an inverter though, I suspected it would be quite inefficient. When cruising, I just used ice. Don't know if it can be done with a modern dorm fridge, since they don't have the exposed condenser coils on the back any more.
Now I have small Frigoboat unit and despite having to fix freon leaks and adding a drier, I like it. Worth the trouble.
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Old 07-12-2017, 18:00   #17
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

The mini fridges that I use are 2 ft X 2 Ft X 3 ft tall and draw 0.3 amps @ 120 Volts. Multiply that by 10 equals 3 amps @ 12 volts. Maybe check your math again. These days a normal 16 Cu Ft fridge/freezer draws about 0.8 A @ 120 V
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Old 07-12-2017, 18:31   #18
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Quote:
Originally Posted by Rorzech View Post
The mini fridges that I use are 2 ft X 2 Ft X 3 ft tall and draw 0.3 amps @ 120 Volts. Multiply that by 10 equals 3 amps @ 12 volts. Maybe check your math again. These days a normal 16 Cu Ft fridge/freezer draws about 0.8 A @ 120 V
your math is correct however must also add 1 amp for inverter inefficiency.
The formula is actually .3 amps x 120 volts = 36 watts. 36 watts x 12 volts = 3 amps.
( Always convert to watts so I don't miss anything.)
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Old 07-12-2017, 18:57   #19
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Yes, you're absolutely correct. I but I'm sure there are some better inverters out there. I've lived off grid for 15 years already. Maybe big inverters are more efficient. Can't remember way back when I bought it .
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Old 07-12-2017, 19:29   #20
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Also don't forget the 10x upsize of the inverter to carry the refrigerator start draw.
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Old 07-12-2017, 19:39   #21
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

I prefer to ignore mains.

How many AH draw over 24 hours with X temp differential? is what I pay attention to.

2-6A while the compressor's running, translates to ~15-60AH per day.

Using an inverter on a mains fridge, even a "very efficient" one in that world, usually means double that.
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Old 07-12-2017, 20:09   #22
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Quote:
Originally Posted by john61ct View Post
I prefer to ignore mains.

How many AH draw over 24 hours with X temp differential? is what I pay attention to.

2-6A while the compressor's running, translates to ~15-60AH per day.

Using an inverter on a mains fridge, even a "very efficient" one in that world, usually means double that.
explain the double statement please ( for this example I'm using the 3 amps mentioned)
my take would be 3 amps for refer and if you get a decent inverter you will loose .5 amps due to inefficiency. So 3.5 amps with approx 15 min per hour so 6 hours running per day. Would mean 21ah. Now a decent inverter uses about .1ah in standby so an additional 1.8 ah. Which would mean 22.8 ah in my cruising area with a cabin temperature of 65įf.

Now with my 400 watts solar it would take about 3 hours this time of year to get that back..( in summer the cabin temp would be 70 to 75. So likely would add about 30 min running time per day. Get that back in less than 1.5 hours. ) my big problem would be where would I put the compressor.
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Old 07-12-2017, 20:40   #23
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

I wouldn't have an inverter/charger less than 2 kW on board. There's only a few good ones out there like Outback, Xantrex/Schneider, Midnight Solar, all designed by an engineer named boB . boB's son also an engineer, designed the Magnum ,also top notch inverter/charger.
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Old 07-12-2017, 20:46   #24
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Yes , I would not put the compressor close to where you lay your head to sleep. The condenser could be put under your composting toilet to provide warmth for faster bacteria production to break down organic matter.
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Old 07-12-2017, 20:59   #25
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

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Yes , I would not put the compressor close to where you lay your head to sleep. The condenser could be put under your composting toilet to provide warmth for faster bacteria production to break down organic matter.
nope a few problems with that
1) wrong side of the boat.
2) still close to where I sleep.
3) head is already getting full between the composter, the urinal , and my watermaker. but it would provide a warm seat in winter
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Old 07-12-2017, 21:04   #26
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Quote:
Originally Posted by Rorzech View Post
I wouldn't have an inverter/charger less than 2 kW on board. There's only a few good ones out there like Outback, Xantrex/Schneider, Midnight Solar, all designed by an engineer named boB . boB's son also an engineer, designed the Magnum ,also top notch inverter/charger.
on another boat I ran an old bar fridge off of an elcheapo harbor freight 750 watt modified wave unit for a couple years.
( having an inverter that runs at 75% to 85% capacity is more efficient )
on my boat I have that 750 watt msw unit and soon to have a 2500 watt psw unit.
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Old 07-12-2017, 21:15   #27
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

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explain the double statement please
My world is 12V, if I go for three weeks with no dino juice, no AC power at all I'm happy.

Including no usage of any inverter.

Therefore "amps at 115V" does not even come into my zeitgeist.


Not just talking inverter overheads, although many don't realize how wasteful they are.

Devices designed for that use case are far more efficient than anything from mains world.

Now go back and see if it's more clear.
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Old 07-12-2017, 21:52   #28
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

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My world is 12V, if I go for three weeks with no dino juice, no AC power at all I'm happy.

Including no usage of any inverter.

Therefore "amps at 115V" does not even come into my zeitgeist.


Not just talking inverter overheads, although many don't realize how wasteful they are.

Devices designed for that use case are far more efficient than anything from mains world.

Now go back and see if it's more clear.
my world uses both 12v Dc and 120v AC it also like yours uses no dino juice ( save a couple pounds of propane) I do just fine with solar and wind.
Why deny yourself a few pleasures from the 120 AC world.

BTW a watt is a watt regardless of voltage.
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Old 07-12-2017, 21:58   #29
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

Quote:
Originally Posted by john61ct View Post
My world is 12V, if I go for three weeks with no dino juice, no AC power at all I'm happy.

Including no usage of any inverter.

Therefore "amps at 115V" does not even come into my zeitgeist.


Not just talking inverter overheads, although many don't realize how wasteful they are.

Devices designed for that use case are far more efficient than anything from mains world.

Now go back and see if it's more clear.
you still haven't explained your statement on doubling of power used.
quote:

2-6A while the compressor's running, translates to ~15-60AH per day.

Using an inverter on a mains fridge, even a "very efficient" one in that world, usually means double that. End quote.
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Old 07-12-2017, 22:02   #30
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Re: Tearing apart a mini fridge and use it for the built in coolbox?

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