Actual Fridge Power Consumption

[kevint]

This may not be the right area for this question but I suspect that the people who frequent this area are the most likely to have the information I want. I read a lot from people who say they ran their 12 v fridge for x days and they still could start their car with no problems. I understand that many fridges have low voltage cutoffs (e.g 11.5) volts but I'm really curious about the range of actual current draws of 12 volt fridges in the +/- 40 liter range.

According to the charge curves published for the Trojan T-105s I have, a low voltage cutoff of 11.5 volts would have depleted my batteries by 90% before shutting down the fridge and popular opinion seems to be that regularly depleting my batteries below 50% is a bad practice.

From reading reviews and articles, for planning purposes, I have been assuming that at 12v I might expect to use roughly 27 amp-hours in a 24 hour period for this type of fridge in moderate temps. This may be low as I suspect that the few amp readings I have seen reported were probably actually made closer to 13.5 volts than 12.

Has anyone actually made the measurements on your fridge? I know there will be lots of variables but I'm just trying to calculate how many days, on average, my batteries can stay above 50% with the types of loads I might expect if I added a fridge. Getting a range of numbers I could average would thrill me. Mostly what I want to know is if my 27 amp-hour per day estimate is fair.

Thanks.

[goodtimes]

T
Has anyone actually made the measurements on your fridge?

Yes.

ARB 50qt, approx 1 year old, no transit bag (cover), in my garage (low temp around 70*, high somewhere around 90*), 24 hour cycles without opening the fridge (IE: not adding any warm items that would need to be cooled off, etc), I saw just under 23 amp-hours per day (24 hours), measured with a Doc-Watson.

[kevint]

Yes.

ARB 50qt, approx 1 year old, no transit bag (cover), in my garage (low temp around 70*, high somewhere around 90*), 24 hour cycles without opening the fridge (IE: not adding any warm items that would need to be cooled off, etc), I saw just under 23 amp-hours per day (24 hours), measured with a Doc-Watson.

Great answer Goodtimes! Do you also know the actual voltage too?

[wrcsixeight]

I have a 1.7 cubic foot front loading AC DC Norcoldt.

It uses, on average, 1 amp per hour to keep it 38 degrees F or below.

My voltage pretty much never drops below 12.2. I have 200 watts of solar.

That 11.5 volt cut off is under load. With the load removed for an hour or 2 the voltage would likely rebound to the 12.0 to 12.2 range which would give the more accurate % of capacity remaining

[goodtimes]

Great answer Goodtimes! Do you also know the actual voltage too?

I don't recall exactly where it ended up at. I started each test with a full charge, ran it for 24 hours, then recharged it overnight before beginning the next test.

[kevint]

Sounds like 27 amp-hours per day is pretty good, hopefully a hair conservative.

[pods8]

Yes.

ARB 50qt, approx 1 year old, no transit bag (cover), in my garage (low temp around 70*, high somewhere around 90*), 24 hour cycles without opening the fridge (IE: not adding any warm items that would need to be cooled off, etc), I saw just under 23 amp-hours per day (24 hours), measured with a Doc-Watson.

I ran my fridge for 6days and had to make some power assumptions off battery voltage only (didn't have a doc watson at the time) and figured it pulled .87amps on average. http://www.expeditionportal.com/foru...ltage-readings

I have a doc watson now and was planning to repeat the test but was waiting for warmer weather.

[cnynrat]

I think Overland Journal did a pretty thorough fridge test a while back that included some pretty detailed measurements under various conditions.

[kevint]

The Overland Journal article was the basis for my 27 amp-hour per day estimate. Thanks.

[witt]

That's pretty much what I saw with my National Luna 50L split (fridge and freezer). I plugged it to AC power in in my garage, which was pretty cool at the time, probably around 65-70 degrees, using a Kill-a-watt to record power usage.

I put a couple of water bottles full of room temperature water in it, and set the fridge at 5 deg C. I let it run without opening it for 24 hours, and the kill-a-watt recorded a total consumption of .22Kwh. At 12V, that would be 20Ah. Assuming a warmer environment and opening the fridge periodically to extract a cold one, it seems like 27Ah is a reasonable number.