AC Fridge In Campervan -.Power Consumption Test

#1
My campervan will have no Gas on-board so a 3-way Fridge is neither an option or something I would want anyway, so Electric-only is my solution.
Due to the high price of DC Compressor Fridges, after some research I decided to install an AC Compresser Fridge.

This post (and some future followups) will show the kind of power usage to expect and if the Electrical setup is sufficient if anyone else is interested in a similar project.
My own setup (400W Solar Array + 440Ah AGM Battery Bank) will be I know,but this analysis may be useful for others interested in a similar option.

INSTALLATION
Fridge: Class A++ 94L Fridge with icebox - £170
(Class A/A+ are available for less, but significantly less efficient. A 12V DC Fridge of comparable size will be around £700)
Inverter: I am using an Inverter. Type is not part of the test and is not relevant.

Below is a video showing power draw into the Inverter (so it includes the energy overhead cost of the inverter as well as the power the Fridge is using). Before Video started, fridge temp dial set to off, Fridge unplugged and Inverter was turned off.

[video=youtube_share;T9JE46VwWxc]https://youtu.be/T9JE46VwWxc[/video]
The times below show the event changes during the video - you can see what is causing the power use to go up and down.

Times:
0:05 - Inverter Switched On
0:20 - Fridge Plugged in
0:30 - Fridge Door Opened (so Light comes on)
0:41 - Fridge Temp Dial turned to Max - Compressor In-rush Current comes on
0:45 - In-Rush Current ends
0:53 - Fridge Door Closed (so Light off)

Note that the power use you are seeing from 0:45 is the maximum power draw all the time the fridge is actively cooling, which is a small percentage of the time on a Compressor Fridge (this is what makes them so efficient in use)

After the video ended I changed the temp dial setting to the normal running one

The Power Monitor in the video records both instantaneous power use and also cumulative power over time. I reset it before commencing the test so can check what power has been drawn by Fridge+Inverter over time.
This testing is being carried out in the winter in an unheated Camper. In warmer weather the Fridge would have to work harder and so use more power, but the same is true of any Fridge of course. When Weather permits I will repeat the experiment.


Notes:
The in-rush current occurs on Compressor Fridges, both AC and DC - this high albeit very short current spike is why it is so important to wire up a DC Compressor Fridge with substantial cable (4mm+ depending on length of run) even though the provided specs of a 12V Fridge might imply a much thinner cable is sufficient with a quoted 3-4A current draw.
If the only use of an Inverter is to run an AC Fridge, that extra cost might make this option not as price-attractive, but if your Camper is using the inverter for other purposes so you will have it anyway, there is no additional cost incurred.
 
#3
So will this Vehicle be for ‘Live in Heavy or Occasional Light Use’ as I actually like the set up you have got or intend having.
Your findings look great & sustainable as posted, Have you done a longer field test in proper longer everyday use use ?.
I don’t have a Heavy Main Use inverter fitted anymore (Use to have a Mastervolt 2500w Pure sinewave that done everything) Brilliant bits of kit, But I just have i Small portable micro one now of 150w & a 300W one on my Portable Power Pack opting for a decent Genny installation for my Power Demands nowadays.
I Do have Gas, But my 22lt Refillable bottle has lasted me close on 14 months now & has Still got 5lt left in it.
No Solar, No Big Battery Banks, No Gimmick or super Gismos just Domestic Appliances Where possible Through out.
 
#4
So will this Vehicle be for ‘Live in Heavy or Occasional Light Use’ as I actually like the set up you have got or intend having.
Your findings look great & sustainable as posted, Have you done a longer field test in proper longer everyday use use ?.
I don’t have a Heavy Main Use inverter fitted anymore (Use to have a Mastervolt 2500w Pure sinewave that done everything) Brilliant bits of kit, But I just have i Small portable micro one now of 150w & a 300W one on my Portable Power Pack opting for a decent Genny installation for my Power Demands nowadays.
I Do have Gas, But my 22lt Refillable bottle has lasted me close on 14 months now & has Still got 5lt left in it.
No Solar, No Big Battery Banks, No Gimmick or super Gismos just Domestic Appliances Where possible Through out.
In terms of longer term testing, the Fridge has been continuously connected to an inverter (going to leave what type unspecified for reasons that are clear!) since November and mostly running on the battery bank with no EHU ( I do plug in occasionally as my Starter Battery is shagged and need to boost it frequently. I also wanted some heat inside when working)
My results to date are that the fridge+inverter combo power needs are generally supplied by the Solar Array when parked up (note how I am parked up below as well)
There is a "fridge is doing little as so cold anyway in winter" argument - there is truth in that I am sure, but on the flip side, the solar is not providing close to its potential due to a) the time of year and b) how I have to park when at home (Due North in the shadow of a 3-storey house). so when out and about it will be a different story in terms of harvesting and I am expecting to harvest way more than the Fridge demands. With my previous Camper I had a Weaco CRX-50 and the 220Ah Battery Bank with 200W Solar Array feeding it would typically be nearly full again by around 10AM in the summer

The reason for this test is to put some solid and specific data to backup (or refute?) my findings. The Class A++ Fridge I bought is spec'ed to consume around 84kW per Annum - that is 218Wh per day, so in typical '12V speak' 18Ah a day, or just 0.75A average draw over the day - lower then a Dometic Weaco CRX-50 average draw. Pretty impressive but does it really deliver and what about the Inverter overhead? Two common questions that are worth answering.
I normally have the Fridge on a Victron Inverter where I can monitor via their Bluetooth App the instantaneous power being drawn, but the Fridge is actually drawing power for so little time, I actually have yet to see it register! (I have put other loads on the inverter just to make sure the app works - it does!!).
Hence fitting a Power Monitor directly onto the Inverter to see the usage and also record consumption over time. This will be the proof of the pudding :)

Reason for No Gas? I am far more comfortable with Electricity then Gas basically for various reasons.
Having no gas however means Hookup, Generator or Big Battery Bank. I went Big Batteries as wanted to be self-sufficient and be able to use power on demand when I need it, like you would at home (within reason!)

My plan is to use my Camper as: a Holiday Vehicle; As a workshop and be able to use mains powered tools if I need; Plus an alternative to hotels if working away.
I found my previous 200Ah Battery Bank pretty ok for that power tool use, but I did have a Gas Hob in that. As I will be cooking with an Induction Hob I might well need more power and recharge more - so doubled the Battery Bank and Solar Array.

Backups ... Small Portable Gas Hob and Cadac Gas Grill for outdoor use; Hookup Connection available of course (I have the wiring setup so the kitchen AC sockets will power off EHU or off Inverter, switching automatically to whichever is availble), and Split-Charge from Alternator (when I get round to installing that). I haven't discounted the idea of a generator either, but I am hoping (expecting) it will not be neccessary.
 
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#5
As I’ve said many times on here before I am a firm believer in doing what works for you & your lifestyle or requirements as we are all different & use our vehicles differently. Part n Parcel of that is offering ideas or intentions up for debate.
So well done you, Brilliant information posted & Thanks will be looking forward to updates.
 
#6
24 Hour Consumption Update

First Power Consumption Update

Firstly, I have installed a 2nd Power Monitor onto the Victron Inverter, and also printed off a couple of Boxes to put the Monitors into to both protect them and identify between the two more easily.
The GREEN Box is the 1000W Inverter (that the Fridge is currently connected to)
The BLUE Box is the Victron 12/500 Inverter

Firstly, Time and Temp:
IMG_20180304_153000 by David, on Flickr
So info taken within a few minutes of first 24 Hours after initial start test.
IN Temp is the Campervan interior
OUT Temp is actually the Fridge internals - -0.1C so a little low in fact, but I'll leave it as it is
CLOCK is the Time of Day :)

Power Consumption over the first 24 Hours:

The GREEN Monitor is the Primary one here
IMG_20180304_152944(1) by David, on Flickr

GREEN Top Right - Current (A):
This is the Current Draw in Amps - at the time this photo taken, fridge compressor off so so no power is being drawn. So the current displayed at this point is 100% Inverter Overhead (confirmed by briefly unplugging fridge and the number didn't change)
GREEN Bottom Left - Power (W): Current Draw in WATTS - This is simply Current x Voltage (P=IV).
GREEN Bottom Right - Power Consumed over Time (Wh): This is what we are interested in! So the Fridge+ Inverter has consumed 270Wh in the last 24 Hours.
This relates to an average of 11.25W per hour, or 0.9A per average average.
In '12V DC' Parlance, that is around 22Ah per 24 hours.


This is what Dometic claim for the Weaco CRX-50:
1.19 Ah/h at +25°C ambient temperature, 2.0 Ah/h at +32°C ambient temperature, both at +5°C interior temperature

In this current cold temp, it is impossible to do a direct comparision, and I don't intend heat up the interior to 25C for days just to do a test (that can wait until nature heats it up for me), but I think already we seem to be in the same ballpark.

It is not possible to work out the 24 Hour Overhead of an Inverter with no-load and just remove that figure from the total consumption to see how much power has been consumed by the fridge, but what I will do is connect an AC Wattmeter into the equation, which WILL give us fridge consumption. If the inverter is purely for the Fridge, that difference is irrelevant, but if the Inverter is used for other required devices as well, then the Inverter overload should be taken as shared (hope that makes sense)

NOTES:
Looking at the other Monitor, BLUE Top Right is 0.62A - This represents the no-load Inverter overhead. Victron make pretty well the most efficient Inverters, so the difference between the Victron and the cheap 1000W Unit is surprisingly small. The ON-Load number might tell a different story?
There is a difference between the voltages (Top Left) on the two monitors - that will be partly down to the positions I am taking the power from (each one from the respective Inverter feeds) and also tolerances of the Monitors ( difference between 12.87V and 12.93V is just 0.5%)
 
#7
My Word,,,Fair play to you,
You really have gone into it with some FANTASTIC information to back it up !.
Way over my head though as I get ‘Figure Blind’ lol
 
#8
I am not an electrician , and lost the plot, you specifically mention the irrelevance of the inverter yet its performance seems crucial to your outcome. That tells me you are either trying to sell me something or the theory despite 101 figures is probably flawed

So why was it not important to mention the inverter ? Sorry for being the "thick one " that asked the question but I suspect other members are wondering the same,

we will leave it at that for the time being

Channa
 
#9
I am not an electrician , and lost the plot, you specifically mention the irrelevance of the inverter yet its performance seems crucial to your outcome. That tells me you are either trying to sell me something or the theory despite 101 figures is probably flawed

So why was it not important to mention the inverter ? Sorry for being the "thick one " that asked the question but I suspect other members are wondering the same,

we will leave it at that for the time being

Channa
The inverter model WILL make a difference but not a significant one. That is the reason and I don't want the thread to go down an irrelevant rathole. I stated the exact model of inverter in an earler thread and ended up with a member discussing Amazons policy on product description. Yeah, right, very relevant to Fridge consumption.

Not trying to sell anyone anything, just imparting information from some testing that I would be doing anyway and which may be of interest to others.
What does "theory despite 101 figures is probably flawed" mean? I don't understand?
 
#11
Firstly I think I will apologise for the verbose waffle in these posts (and probably all my posts!). I tend to want to know all the background to things and end up assuming others do as well! (this is why when I worked on the technical help desk at Dell, I used to do about half the calls of most others - not that I worked less, but just spent longer explaining why something wasn't working :lol-053: )

So I will try and cut to the chase and suppress the waffle until the end so can be more easily avoided!

48 Hours into the Testing

Power used in first 24 hours was 270Wh; Power used in second 24 hours was 300Wh (total of 570Wh).
Doing some sums, this means the Fridge seems to consuming between 30-37Wh a day. That is VERY low and while I am sure it is right, it is due to the cold temperatures and not representative (the maker quotes 230Wh a day and that would I imagine assume fitted in a house with a room temp around the 20C mark so more cooling is needed)

So it won't be until say May that I will be able to reliably compare against quoted Weaco numbers. Right now the Inverter overhead represents nearly 90% of total power consumed. This is because I have worked out the fridge is actually running for only 40 minutes per day! Just 5 cycles of 8 minutes each on average, so for 23 hours, 20 minutes, the power used is just the inverter running on no-load.



Waffly time ....
To confirm the above, I have fitted an AC Wattmeter for the Fridge to plug into - the Power Monitor is reading the total Fridge+Inverter consumption as a whole. The Wattmeter will be reading purely the power consumed by the fridge, so with those two meters, will be able to get the exact Inverter overhead, both off-load AND on-load. That won't be for a day or so.
As per the notes in the earlier paragraph, the actual consumption will not be typical of an annual consumption and need a summer comparision as well to see the full picture.


So in a day or so I am going to switch the Fridge onto the Victron Inverter again, but in a specific mode...

The Victron Inverters have an "ECO" mode where every 5 seconds or so the inverter switches on to Search for a load. If it finds one, the Inverter then stays on until not needed and then goes back to Searching
This is the app in that mode:
Victron - ECO Mode by David, on Flickr
As mentioned in a previous post, I never see the fridge register anything on the App and that is clearly because it is so rarely 'on'.

Difference between ECO mode and ON Mode?
When the Victron Inverter is ON, there is a constant 8W being drawn by the inverter with No-Load
When the Victron Inverter is in ECO Mode, when it is searching it uses 2.3W, and when it is in Standby, it uses 0.6W.
That is a massive difference in power!
I haven't been using ECO mode previously as it needs a minimum power load to turn on when searching and the Fridge Light is not enough so you would open the fridge and every 5 seconds or so the light would flash on and off as the Inverter went to Search mode.

This is a clip showing a few cycles of the Inverter searching for a load when in ECO mode
[video=youtube;Sj-3CY1HtVQ]https://www.youtube.com/watch?v=Sj-3CY1HtVQ[/video]

Now given the fridge only seems to be on for around 40 minutes a day, being able to run the inverter in ECO mode could make a massive difference to overall power consumption. Well, we shall see within the next week I think.
The last 24 Hours showed the Victron using 206 Wh while in ON Mode and no load connected to it. The next 24 Hours in ECO mode with no load connected will be a good comparison.
 
R

r4dent

#12
Power used in first 24 hours was 270Wh;
Power used in second 24 hours was 300Wh (total of 570Wh).
Doing some sums, this means the Fridge seems to consuming between 30-37Wh a day.
I just don't understand these figures ! You state one day was 270Wh and the other 300Wh, so what is the 30-37Wh a day about ?

Did you mean 30-37 ah a day, and if so how did you calculate this?

Interested in the make and model of the fridge, the ones I've been looking at seem to 1-2 kWh a day which would give very different results.
 
#14
‘Could it mean’ (Yep assumptions on my part) -
It was actually 48A used over 48hrs, 270w +300w devided by 12(v) = 47.5 A
BUT
10A (Possibly) put IN from an overlooked Solar panel over this period so ‘CredIt 10A’
= 37 ish A used Kinda, Maybe, ish !,,,

Oh I don’t know, as I suggested earlier Maybe Too complicated & in-depth for my mind
 
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#15
I just don't understand these figures ! You state one day was 270Wh and the other 300Wh, so what is the 30-37Wh a day about ?

Did you mean 30-37 ah a day, and if so how did you calculate this?

Interested in the make and model of the fridge, the ones I've been looking at seem to 1-2 kWh a day which would give very different results.
so day one the total power was 270Wh, and day two was 300Wh - so 10% variance in a day .. reasonable enough.

the 30-37Wh a day represents how much the actual FRIDGE is using seperate from the Inverter overhead.
The Numbers:
  • Inverter when Fridge is Off using 10W - so that is 240Wh a Day;
  • Fridge when On is actually on for around 8 minutes each time and at the time the total power draw is 55W - so over that 8 minutes, the power used is 7.33Wh each time (55W*8/60) and the Fridge comes on 5 times (that is what the maths work out it be be)
  • If you assume 10W Inverter overhead is constant whatever the load, Fridge uses 30Wh in 24 Hours (45W of that 55W when on so 45*8/60 * 5);
  • If you assume NO Inverter overhead when there is a load, fridge uses 37Wh (55*8/60 * 5).


The Actual FRIDGE load is somewhere between the two - the Wattmeter will tell me where tomorrow as it is measuring just the fridge
(as a slight aside, the Wattmeter itself is a load - it uses a constant 1W so will be skewing the numbers next time, but none of this test is using scientifically calibrated equipment anyway and 1W is small enough to ignore given all the other variables)

Probably above clear as mud the way I explained it :( (I guess removing the wafflly bits made it shorter but less clear as well)


Choice of Fridge is key. I bought an A++ Energy Rated Fridge. An A+ one is significantly worse and an A rated fridge I would say is a non-starter for general Motorhome use unless you are on hookup up daily.

This is the Fridge I bought: Inventor A++ Silver Mini Fridge, Internal Capacity 93L, Silent, Ideal for house, office and dormitories, Max Storage Capability, Energy Savings and Eco-Friendly: Amazon.co.uk: Large Appliances
Selected for combination of A++ Energy Rating and Noise Level (42dB)
I have been saying it is 84kWh but just reading specs again it is just 80kWh in fact

As a comparison, THIS Fridge - Statesman R155S Under Counter Fridge with 4* Ice Box, 55cm, Silver: Amazon.co.uk: Large Appliances - is Classed A+ but its energy consumption is 137kWh
There are not many newish fridges around running at 1-2kWh a day? (that would mean the official energy sticker would state 365-740kW (numbers quoted on them are per annum)
A Fridge Freezer would use a lot more than just a fridge as well.
 
#16
Any chance you could convert the WH figures into Amps ???
Just divide Wh/12 = Ah

P/V=I --> Power/Voltage = Current; so 270W / 12V = 22.5Ah

(it is tricky with a DC battery to do this Ah calculation reliably. An AC supply is a steady nominal 230V in the UK, so V will always be regarded as 230V for calcs. A DC Battery will be anywhere from 12.0V to 14.4V and drops over time of course when used and not on charge - and with the equation P=IV (an equal of P/V=I), as the voltage lowers, the current required to deliver the same power must increase. This is why I stuck to Watts)


‘Could it mean’ (Yep assumptions on my part) -
It was actually 48A used over 48hrs, 270w +300w devided by 12(v) = 47.5 A
BUT
10A (Possibly) put in from Solar over this period so ‘CredIt 10A’
= 37 ish A used Kinda, Maybe, ish !,,,

Oh I don’t know, as I suggested earlier Maybe Too complicated & in-depth for my mind
Nope, wasn't 37Ah, but 37W (as per previous reply).
Ref the solar - good thought process but not in this test :; One reason why I fitted the Power Monitors for the test is that while I have a Battery Monitor which is very good (Victron BMV-712), it is a Systems-wide monitor, so Solar harvesting would skew it one way; putting lights on will skew the other and using that would tell us very little.

So ... I am monitoring the load specifically out to the Inverter, so any other loads - say lights, for example, or any charging in from Solar or Battery Charger will have no effect on the test other then to make the DC Battery voltage lower or higher (skewing the Ah values in the process, which is why I am using Watts as that is not effected by voltage (as per the note to mistericeman).


In actual fact, I have not had any Solar Harvesting at all for around 5 days (snow covered panels) and only got some again this morning when I decided to clear off the panels as the snow stopped falling last night. The Battery charger has not been connected into the Leisure Battery either for around 3 days, so the 12.93V level of the battery we see at 3PM yesterday is pretty nice :)
 
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#18
Day 3

72 Hours into Testing

It is getting warmer now and I think that means the fridge needs to start working a bit more to keep to the set temperature, going by the power consumption

After 24 Hrs: Monitor shows 270Wh - Power used in first 24 Hrs = 270Wh
After 48 Hrs: Monitor shows 570Wh - Power used in second 24 Hrs = 300Wh
After 72 Hrs: Monitor shows 905Wh - Power used in third 24 Hrs = 335Wh

I fitted an AC Watt Meter to the Inverter Output Socket and that shows the Fridge itself used 90Wh in the last 24 Hrs.
The Manufacturers quote 220Wh/Day. 90Wh to me sounds pretty understandable considering the cold test environment compared to a kitchen and that the Fridge Door is never opened between Test intervals, so no heat loss from that occuring (or light on).

This 90Wh also ties in very well with the previous info, which indicated the Inverter Overhead was 10Wh an hour off-load.
So if the inverter was on for 24 Hours, it would consume 240Wh. Add in the 90Wh the AC Watt Meter recorded for the fridge and you get 340Wh total. The Battery Power Monitor gave us a total for the last 24 hours of 335Wh - that is just about only a 1% variance.

So finally can make some first conclusions* about something in the test!
  • The Inverter consumes a constant 10Wh per hour regardless of off-load or with-load
  • The Inverter Overhead is likely to be around the same as the likely power consumption of the Fridge in typical operating conditions (220Wh/Day as noted previously by Manufacturer)
Extrapolating into normal operating temperature and usage based on Manufacurers Specs, I am concluding that: For a AC Class A++ Fridge running off a typical Inverter, expect a Power Usage of 460Wh per day.
This equates to around 38Ah/Day, or a constant 1.58A.



*This may not be the case with a higher load - The Fridge has been only 10% of the Inverter Capacity. I will carry out a test with a higher load and check.



Now let's look at the Waeco CRX-50 Specs again: 1.19 Ah/h at +25°C ambient temperature, 2.0 Ah/h at +32°C ambient temperature, both at +5°C interior temperature
1.19Ah/h Average equals 14.28Wh (based on DC Volts being 12V), which is 342Wh/Day - far less efficient then the AC Fridges 220Wh/Day Average.

With the Inverter used in the test adding in 240Wh, the AC Fridge Option (using Manufacturer power of 220Wh/Day) draws an average of 0.39Ah/h (9.36Ah/Day) more than the DC Fridge - that is under 5W an hour, around the same as an interior light left on.

With a better Inverter, it is very likely the Inverter+AC Fridge Combination will have a LOWER total consumption then the dedicated DC Compressor Fridge.
This will be is my next test



I have now unplugged the Fridge from the 1000W Inverter and inverter is turned off.

My Testing has now moved onto using the Victron Inverter in ECO Mode - this is a better inverter then the one used in the testing above, but is also significantly more expensive.
I will post first data from the Fridge+Victron Tests tomorrow.
 
#19
Fascinating,so now we know what retired/ex dell techs do :)
I will read and understand hopefully

regards Pete
dell/emc customer service engineer retired :)
 
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