Engel Fridge 745 hour Kill A Watt #'s

[mnpaul]

Hello, I've been running my Engel MT45F-U1 43quart refer for a month plugged into a Kill A Watt meter.
It's been inside plugged into 120 volt AC.  My last readings:
745 hours   9.93 KWH
About how many battery AmpHours would this need in a day?

 

[Spaceman Spiff]

9.93 KWH = 9930 watt-hours
9930 WH ÷ 745 hours = 13.3 watts
13.3 W ÷ 12 volts = 1.1 amps
run for 24 hours -> 1.1 A X 24 hours = 26.6 amp-hours

A couple of additional pieces of information if you know them:

1. what was the ambient temperature range while you were running?
2. What was the inside refrigerator temp?  freezer temp?
3. Did you have anything in the refrigerator or was it empty?
4. Did you open and close the refrigerator periodically or was it closed the whole month?
5. Was the refrigerator in a cabinet or was it sitting on a bench?

Thanks for the info.

 -- Spiff

 

[John61CT]

also note that usage off 120V may well differ a bit from that off 12V. Maybe under 15-20% difference, but worth being aware of. . .

 

[Weight]

the compressor fridge may draw 2 amps when running but it cycles as it regulates the temp.

 

[John61CT]

9.93 KWH = 9930 watt-hours
9930 WH ÷ 745 hours = 13.3 watts
13.3 W ÷ 12 volts = 1.1 amps
run for 24 hours -> 1.1 A X 24 hours = 26.6 amp-hours

Nit picking here, math is fine, just conceptually, Watt hours and Amp hours are actually fundamental quantity units, not "per time".

So KWH per 31 days yields 320 whWH per day, then just divide by ~13 if you want 25 AH per day.

Like I said, nits, sorry.

 

[user 37446]

Good thread, gives people wanting a 12v compressor fridg an idea of usage, 2 amps per hour being a good planning amount for batteries... Not knowing the temps, fill capacity, duty cycles, # of times opened etc...

 

[mnpaul]

also note that usage off 120V may well differ a bit from that off 12V. Maybe under 15-20% difference, but worth being aware of. . .

Thanks John, would that be an increase or decrease in consumption?

 

[mnpaul]

Fridge conditions: Inside, on wood floor, one side about 5 inches from wall but other wise plenty of circulation.
No added insulation to fridge body(may add later for vehicle use)
Did not keep track of ambient temp. but we've only turned the air on a couple of times and often the inside air has been in the mid to high 70's.
Several days inside temp has been 85F+
Was using it as a 2nd fridge so opened less than normal but did have the staples of life inside(eggs, beer, cheese, oj etc.) so it was opened several times a day.
Kept food just below 40F as measured by one of those infrared pointer thermometers.
First couple weeks it was pretty full.  Last 10 days little less than 1/2 full.

 

[Spaceman Spiff]

also note that usage off 120V may well differ a bit from that off 12V. Maybe under 15-20% difference, but worth being aware of. . .

Is that because the refrigerator using a converter to change 110V AC to 12V DC (i.e. conversion loss)?  Seems like a lot of loss.

Nit picking here, math is fine, just conceptually, Watt hours and Amp hours are actually fundamental quantity units, not "per time".

So KWH per 31 days yields 320 whWH per day, then just divide by ~13 if you want 25 AH per day.

I think I understand what you are saying:  if I use 6 amps for 10 minutes I have used 1 amp-hour?

1000 WH ÷ 31 days = 32.26 WH per day, what is whWH (WH X 10)?
  from Wikipedia: "[font='Helvetica Neue', Arial, sans-serif]WHWH is a radio station in Princeton, New Jersey, serving Trenton, New Jersey."[/font]

Where does divide by 13 come from?  Why not 12 volts?

Just trying to understand.  Always had EE's to hold my hand when doing this stuff at work.

 -- Spiff

 

[John61CT]

Is that because the refrigerator using a converter to change 110V AC to 12V DC (i.e. conversion loss)?  Seems like a lot of loss.


I think I understand what you are saying:  if I use 6 amps for 10 minutes I have used 1 amp-hour?

1000 WH ÷ 31 days = 32.26 WH per day, what is whWH (WH X 10)?
  from Wikipedia: "[font='Helvetica Neue', Arial, sans-serif]WHWH is a radio station in Princeton, New Jersey, serving Trenton, New Jersey."[/font]

Where does divide by 13 come from?  Why not 12 volts?

Just trying to understand.  Always had EE's to hold my hand when doing this stuff at work.

 -- Spiff

Sorry typo, WH or wh is watt hours, quantity of power.

Voltage affects amps measurement, between 12-13 depending on many factors so in fact WH is better more absolute.

The inefficiency factor is unknown, just saying, use an AH-counting battery monitor to be accurate for mobile DC usage tracking.

Yes, 6A constant usage rate over 1/6 of an hour is 1AH.

 

[Spaceman Spiff]

Sorry typo, WH or wh is watt hours, quantity of power.
Didn't think you were talking about a radio station in New Jersey 

Voltage affects amps measurement, between 12-13 depending on many factors so in fact WH is better more absolute.

OK, understand why you used 13V.  Batteries are at ~12.7V when full, ~12.1V when at 50%.
I agree: less confusion with watts and WH, although the converter/inverter inefficiencies muddy the waters too.

Thanks, mnpaul.  Conditions are what could be called 'normal usage'.

 -- Spiff

 

[user 37446]

Dividing by 13 allows for small, long DC wire and other inefficiencies. If you used an inverter there's 10-20% efficiency loss there as well. Insulating around your fridg is important, all sides and top, just keep vents open. Bob Wells has a video on it.

 

[Travelmonkey]

It is amazing the efficiency of these fridges. One could probably get away with 100W solar and a single battery most of the year. Thanks for posting data and math.

 

[SternWake]

For just the fridge, in a cooler ambient temp environment, some can get away with as little as 60 watts.

As efficient as they are, they can be improved upon with better airflow across/through condenser and more insulation.

And of course by not heating the too thin copper and resistive Ciggy plugs and receptacles that feed it power.

 

[highdesertranger]

I run 2 Engels off of 2 80 watt panels and 2 group 31 marine batteries no problem. plus I have enough left over to recharge the lap top and other misc. stuff. if I was to redo it today I would use two 100 watt panels. highdesertranger

 

[galladanb]

Hello, I've been running my Engel MT45F-U1 43quart refer for a month plugged into a Kill A Watt meter.
It's been inside plugged into 120 volt AC.  My last readings:
745 hours   9.93 KWH
About how many battery AmpHours would this need in a day?

Thank you for this data! I have a similar engel.

After recovering from our first trail run, I will be posting some system questions...
Your data will assist me!