Actual Fridge Power Consumption

[kevint]

Thanks for the watts, Witt.

[4x4junkie]

I ran some tests awhile back on my Edgestar FP430 and found it consumes 44.8 Ah over a 24 hour period at 12.5V to maintain an internal temp of 30° inside of a 80° room.

The OJ article I read had all the tested fridges of similar size ranging from 42Ah to 66Ah of power consumption under the same controlled conditions (I understand there's a more recent review than that one, however I have not been able to find it posted anywhere, so that's the only info I have to go by).
Amp-hour figures in the low-mid 20s seem like they'd be typical for a fridge left alone in a semi-cool garage out of the sun, however it'll be harder to estimate consumption in actual use since it varies tremendously with ambient temperature and how often you open the lid on it (I've seen mine not run once from sundown to sunrise on cool nights, but will be running maybe 50-60% of the time if inside the vehicle and it's over 90° out).

I suspect a worst-case average might be around 50-60Ah for a fridge of this size on a hot day followed by a warm night.

[kevint]

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.

That's a great comparison for me. First of all, your setup is so similar. Your two 6v batteries rate at 210 AH and mine at 225 AH. I'll consider that "safety factor." According to the published capacity curves for my batteries, they are at 65% of initial capacity at 12.3 volts. You were at 12.34 volts and may not have given them enough time to fully recover from their primary load so that is a little more safety factor. You are also running your fridge at 32 deg-f which is a little colder than necessary, I think. More safety factor. Ratio-ing from 35% depletion to 50% depletion would get me a little over 8 days with your system, settings and ambient temps. That's far more than I'd hoped for.

Thanks.

[kevint]

I ran some tests awhile back on my Edgestar FP430 and found it consumes 44.8 Ah over a 24 hour period at 12.5V to maintain an internal temp of 30° inside of a 80° room.

The OJ article I read had all the tested fridges of similar size ranging from 42Ah to 66Ah of power consumption under the same controlled conditions (I understand there's a more recent review than that one, however I have not been able to find it posted anywhere, so that's the only info I have to go by).
Amp-hour figures in the low-mid 20s seem like they'd be typical for a fridge left alone in a semi-cool garage out of the sun, however it'll be harder to estimate consumption in actual use since it varies tremendously with ambient temperature and how often you open the lid on it (I've seen mine not run once from sundown to sunrise on cool nights, but will be running maybe 50-60% of the time if inside the vehicle and it's over 90° out).

I suspect a worst-case average might be around 50-60Ah for a fridge of this size on a hot day followed by a warm night.

Thanks for the info. I like the worst case scenario. Sounds like I might be able to plan for 24 - 50 AH per day depending on variables.

Did you let the fridge and contents come to temp before you started your test. That is the assumption I based my initial estimates on. If I get a fridge, I'll do my best to get it loaded and cooled down before switching to DC power. Based on your setting of 30 deg-F I guess you are running in freezer mode. Did you actually get cold enough to freeze?

Thanks.

[pods8]

You are also running your fridge at 32 deg-f which is a little colder than necessary, I think.

A normal fridge runs about 35-38deg, with the ARB I know the thermostat is located at the bottom so you gotta set it a bit lower. On trips I was running it on 28F fully loaded up w/o really freezing anything but also keeping everything cooled. When I've ran it as a freezer I've set it in the 0F-6F range (I keep it on 0F unless it seems to be running a lot during the hot part of the day in which case I'll bump it up a few degrees and then drop it back down over night to lesson the load).

We'll be going out for a weekend jaunt in a couple weeks and I'll run it though the doc wattson to see what numbers I get with the family going in/out of it for a couple days. However we've been having lousy cool weather so it might not be working too hard.

[4x4junkie]

Did you let the fridge and contents come to temp before you started your test. That is the assumption I based my initial estimates on. If I get a fridge, I'll do my best to get it loaded and cooled down before switching to DC power. Based on your setting of 30 deg-F I guess you are running in freezer mode. Did you actually get cold enough to freeze?

Thanks.

I was mimicking the test procedures outlined in the OJ article as exact as I could so I could get an idea where my Edgestar unit placed in reference with the others. It was left to stabilize for some hours with twenty 12-oz drink cans in it before I started taking measurements for the above (I was intending to post my full findings in another thread here but then I discovered the article wasn't the most recent one so I put it off it until I had reviewed the later one. But alas... I've had no luck finding the later one anywhere short of ordering a printed back-issue from OJ. )


As for freezing stuff, I can set the thing to as low as -8°F. I've never had a reason to leave it at that setting, though I have used 0°F, which it cooled to and held that temp with ease.
Normally I set the control for 35°F, which is 1 degree above where ice crystals would otherwise start forming in stuff (I suspect it's calibration could be off a couple degrees, but it has stayed consistent over the two years I've had it).

[G_fresh]

Here is my contribution.

Just got the National Luna Weekender 50L Split Fridge Freezer a week or so ago.

http://www.equipt1.com/companies/Wee...tainless-steel

I wanted to test it out to make sure it is "expedition ready". So, I tested the fridge with plugged into the wall (AC) and with a 12V lead acid battery (DC).

The garage's ambient temperature varied from 61.3ºF to 82.6ºF over the entire week of testing.

Equipment:

Kill-A-Watt meter to measure the AC kilowatt hours (kWh)
Fluke 87 Series 5 digital multimeter (DMM) to measure temperature
Another Fluke 87 Series 5 to measure DC current from the 12V battery
Fluke 75 DMM to measure voltage of battery
Interstate Mega-Tron Plus, MTP-27F lead acid starting battery

photo 5.jpg

How I tested AC functionality:

0. Put into my garage.
1. Loaded the fridge side with as many water bottles as I could - 20, 1L bottles.
2. Loaded the freezer with about 3L of bottles.
3. Placed a thermocouple about halfway down the fridge compartment in intimate contact with a bottle.
4. Plugged the fridge into the wall, 120V AC.
5. Set the thermostat to 3ºC (37.4ºF) and put onto turbo mode.

photo 2.jpg photo 3.jpg

AC Test Results:

Day 1, 7:20pm, 72.5ºF, 0kWh
Day 1, 10:00pm, 69.7ºF
Day 2, 8:53am, 52.5ºF, 0.61kWh
Day 2, 7:43pm, 43.7ºF, 0.87kWh
Day 3, 8:56am, 38.5ºF, 1.12kWh
Day 3, 5:12pm, 38.0ºF, 1.22kWh
Done

How I tested DC functionality:

0. Fully charged battery.
1. Turned off turbo mode.
2. Plugged the fridge into the battery through the Fluke 87 DMM to measure the fridge's current.
- the current I report below is the running average of the current drawn by the fridge
3. Connected the Fluke 75 to measure the battery's voltage.
4. Only opened the fridge once or twice a day to cheek on things.

DC Test Results:

Day 6, 8:58am, 38.7ºF, Battery Voltage (Vbatt) = 12.65V, 0A
Day 6, 10:46pm, 38.9ºF, 12.62V, 0.967A
Day 7, 11:01pm, 39.1ºF, 12.37V, 0.908A
Day 8, 8:37am, 37.0ºF, 12.29V, 0.883A
Day 8, 9:32pm, 40.6ºF, 12.16V, 0.864A
Done

At this point, I unplugged the fridge but kept it closed. The next day (Day 9) at 3:57pm, the unopened fridge only gained 3.6ºF.

Conclusions:

It took about a day and a kWh to get the fridge to set temperature plugged into the AC line with a relatively large cooling load. So, I say try to plug in before you leave if possible. A kWh translates to about 80Ah for a 12V system. I don't think it would actually take that much energy due to the conversion loss from AC to DC but, that is speculation…

The DC test revealed this is a pretty efficient fridge. Good, because that is what I paid for! It ran off the old battery I had for about 48 hours at an average draw of 0.864A. This equates to 41.5Ah total energy or, about 21Ah for a day. My big 100Ah Sears DieHard Platinum Marine Group 31 batteries should each be able to run five days before being fully depleted in similar, moderate ambient temperatures.

Finally, if one were driving for a few hours everyday, this should make a nice, powered cooler if opening was minimized. This is evidenced by the fridge only gaining 3.6ºF in 18 hours when unplugged.

I do have more data. I only showed beginning and ending of the day data for clarity's sake...

[kevint]

Thanks, G-Fresh. Trend of around 24 AH per day at moderate ambient conditions seems to hold.

Remember that popular opinion seems to be that as a rule you shouldn't take your batteries below 50%.

All this data is very helpful.

[pods8]

Just got back from a weekender: 50qt ARB set at 26F with milk, food and beverages in it. Was in and out of it numerous times all weekend for "daddy" beverages and to get the kids milk, cheese, etc. Wetside PNW "summer" temps were as expected (60s-70s). Running from noon on Friday to 5pm Sunday pulled 32.6ah. 32.6ah/53hrs = .615ah average continuous load for these ambient temps/usage.