Amp hour use

Oct 2, 2008
1,424
Island Packet 31 Brunswick, Ga
What would be the Amp hour use For an upper right 1.1 ft.³ freezer in a boat that is rated at 79W and 1.1 amp hours. To make things worse it will be hooked to a small, let’s say efficient, converter. Question posted on a Facebook boat owners forum.
 
Sep 25, 2008
7,075
Alden 50 Sarasota, Florida
1amp-hr at 12 volts = 12 watts. At 120vac it consumes 120watts.

If your compressor label indicates 1.1amp-hr drawing 79 watts, it was mislabeled. For an inductive load, it might be around 90 watts but not 79.

What does “upper right” mean?
 
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
rated at 79W and 1.1 amp hours.
Sorry, I can't parse that. As Don suggests, 79W is 6.6A @ 12V, and 0.66 A at 120V. 1.1 Amp Hours is a measure of energy used, and I can't see any way to use 1.1 amp hours per hour at any normal voltage. Maybe they're factoring in some assumed duty cycle? For example 79W at 12V is 6.6A, but if it only runs for 10 minutes per hour it will draw 1.1 amp hours each hour. Actual duty cycle would vary based on contents and ambient temperature though.
 
Dec 2, 2003
751
Hunter 260 winnipeg, Manitoba
Assuming this is a dorm style fridge you will also need to consider the likelihood of compressor/tubing burnout. Most compressor style home/dorm style fridges are designed to be almost perfectly level in use - after moving or transport you are supposed to wait several hours for the refrigerant to return to normal level and prevent burnout/hot spots in the tubing, compressor etc.

If you are looking for a low cost solution I would look at some of the more efficient thermoelectrics that run off 12v (up to 86°F below ambient vs 68°f below ambient - 30C vs 20C) or if energy efficiency is more important then some of the compressor styles made for 12/120v operation in boats such as the dometics, isotherm, norcold etc. Would be the choice, but of course are considerably more expensive.

I have used both but in a generally cooler climate. Our thermoelectric ran 2-2&1/2 amp/hr on 12v. Our larger cfx95 seems to run about 1-1&1/2 amp/hr
 
  • Like
Likes: Will Gilmore
Oct 2, 2008
1,424
Island Packet 31 Brunswick, Ga
Wow, great information, and good point twalker. I’ll forward this information. Thanks again. It’s been a while since I’ve been here. Still the best site ever!