rogerthebodger
Well-Known Member
Any one know of a simple electrical meter that I could connect to my 12VDC fridge compressor that would show me the duty cycle (on/off time percentage)
Boat fridge duty cycle.
- Thread starter rogerthebodger
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RAI
Well-Known Member
A battery charge meter might help. Compare, over a long time, the Ah used with the amps when the fridge is on as the only load and with no charging source.
pvb
Well-Known Member
A simple hour meter would give you the information much more easily.
Chalker
Well-Known Member
How accurate do you want.
Really crudely, connect a 12 volt bulb to the fan on the compressor, in a place that you can see.
Check and record if the bulb is on or off lots of times during the day, not necessarily regularly but randomly during the day. If others are onboard they can also record the data.
For each person: % On divided by total number of observations = your answer. Check that your result is similar to others . Same calculation for all the data lumped together should be even more accurate.
But I do like the hours meter even though the 12v bulb is cheaper!!!
Really crudely, connect a 12 volt bulb to the fan on the compressor, in a place that you can see.
Check and record if the bulb is on or off lots of times during the day, not necessarily regularly but randomly during the day. If others are onboard they can also record the data.
For each person: % On divided by total number of observations = your answer. Check that your result is similar to others . Same calculation for all the data lumped together should be even more accurate.
But I do like the hours meter even though the 12v bulb is cheaper!!!
Conachair
Guest
William_H
Well-Known Member
Duty cycle for a fridge can vary so much with ambient temperature that your method will be OK for the period involved but does not necessarily forecast what will happen in any other period. Bu then that very fact makes the whole OP question a bit variable. ie depends on temperature and of course how often the fridge is opened or if you have put in a lot of warm stuff.
An hour meter can show you what has happened eg over the last day and perhaps that could suggest similar tomorrow.
good luck olewill
rivonia
Well-Known Member
There are so many variables here. Not only does it depend on the ambient temperature but also the amount of times the the fridge door is opened, the temperature of items that are put into it, the voltage of the batteries etc etc etc etc etc.
Peter
Peter
charles_reed
Well-Known Member
Yes my fridge uses from 12AH in 24 hours @ UK temperatures to 42AH @ Med summer temperatures in 24 hours - not only dependent on ambient temperature but frequency of opening and whether it's top-loading or a standard front-door.
Mine is top loading and has fairly good (100mm) insulation.
alan
Well-Known Member
Mine, front loading, is about 25 -30% on average.
Alan.
Alan.
charles_reed
Well-Known Member
Alan 25-30% of what?
I'd assume that is how long it runs for out of the total period, based on my compressor draw that's about 40AH in 24 hrs, which seems high for this time of year in the N Hemisphere.
rogerthebodger
Well-Known Member
Thanks guys for your input.
I do already have a LED to indicate when the fridge is running but I get bored watching it so I find I miss the on and off times.
A Hour counter would do the job but it would need to be a resettable one so I could start it a a particular time of day and run it for say 24 hours noting the total on time. The link posted only had one resettable and it was quite expensive. Using 2 resettable with one running all the time and the other running only when the fridge compressor was operating would be the next best to a proper designed duty cycle meter.
I do know the result will depend on ambient temperature but also the amount of times the the fridge door is opened but I would like some kind of indication say over night so the door would not normally be opened and I could note the ambient temperature so I could compare over time.
The main reason is that the on time seems to have got longer over time since installation such that one time last summer the fridge operated continuously during one visit when the ambient temperature was quite high. Yesterday the outside ambient temperature was 35 C (sorry I know it quite could in the UK currently). Of last it has reverted to more "normal" operation but am not sure if their is a fault somewhere.
Amy more comments would be most welcome.
I do already have a LED to indicate when the fridge is running but I get bored watching it so I find I miss the on and off times.
A Hour counter would do the job but it would need to be a resettable one so I could start it a a particular time of day and run it for say 24 hours noting the total on time. The link posted only had one resettable and it was quite expensive. Using 2 resettable with one running all the time and the other running only when the fridge compressor was operating would be the next best to a proper designed duty cycle meter.
I do know the result will depend on ambient temperature but also the amount of times the the fridge door is opened but I would like some kind of indication say over night so the door would not normally be opened and I could note the ambient temperature so I could compare over time.
The main reason is that the on time seems to have got longer over time since installation such that one time last summer the fridge operated continuously during one visit when the ambient temperature was quite high. Yesterday the outside ambient temperature was 35 C (sorry I know it quite could in the UK currently). Of last it has reverted to more "normal" operation but am not sure if their is a fault somewhere.
Amy more comments would be most welcome.
rogerthebodger
Well-Known Member
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RAI
Well-Known Member
Using a battery monitor would allow you to calibrate the duty cycles of every electrical load, as well as its normal function.
Beyondhelp
Well-Known Member
How seriously do you want to do this? It wouldn't be hard to write a program on an arduino or other mcu for example to measure typical duty cycle vs ambient temps.
Chalker
Well-Known Member
watching the light is not continuous, it's whenever you remember it, just not every couple of minutes. If you look at it 10 times a day, widely spaced but not necessarily regularly will be fine for a rough estimate. 20, or 22 or 47 times will certainly be better. Just a random sample is all you need, number of times alight divided by total number of observations. The number of observations can be whatever you remember to do.
With the hours meter, just record what it is at the start and the finish over a day, 2 days, 2 1/4 days or whatever. Minutes used divided by total elapsed minutes from your watch Resettable is certainly not necessary.
With the hours meter, just record what it is at the start and the finish over a day, 2 days, 2 1/4 days or whatever. Minutes used divided by total elapsed minutes from your watch Resettable is certainly not necessary.
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nimbusgb
Well-Known Member
Caerfull Beyondhelp ... You forgot to mention that you could also do it with a pic processor and a bit of soldering 
Yes an Arduino would allow you to capture air temperature, compressor on and off times and perhaps even door / lid transitions, save it all in a file and download it to a pc via usb.
But why bother. Just jot down the temperature and watch the units of leccy used via your battery monitor. If your system is borderline just add another house battery.
Yes an Arduino would allow you to capture air temperature, compressor on and off times and perhaps even door / lid transitions, save it all in a file and download it to a pc via usb.
But why bother. Just jot down the temperature and watch the units of leccy used via your battery monitor. If your system is borderline just add another house battery.
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Beyondhelp
Well-Known Member
Didn't mention the pic MCU since the small devices I've used didn't have a real time counter.
I do agree with you re complexity though. Few years ago I had a camping gaz cool box with peltier element. It would stay on all the time drawing about 4A cont. So made a little thermostat and set the temp to 5 deg. It was quite interesting to see it cutting in and out as the day got cooler and hotter. Varied hugely, made a very noticeable difference to battery life too.
I do agree with you re complexity though. Few years ago I had a camping gaz cool box with peltier element. It would stay on all the time drawing about 4A cont. So made a little thermostat and set the temp to 5 deg. It was quite interesting to see it cutting in and out as the day got cooler and hotter. Varied hugely, made a very noticeable difference to battery life too.
