Isotherm CR49 fridge watt consumption?

[JayGuevara]

Guys,

It says in their spec sheet that this fridge uses 265 (w/24) @5 degrees Celsius with an ambient temperature of 25 degrees C.

So how may amp hours does that draw in a 24 hour period running on 12v DC?

The calculator I just used says 22 ah in a 24 hour period.

Is this correct?

cheers.

 

[John Frum]

According to this https://www.emarineinc.com/Isotherm-CR49

Its average power consumption is 0.45 amps@12 volts = 5.4 watts.
Which is awesome if true.
I don't believe it though.

 

[John Frum]

hmm it also says "*) Average/maximum Amp draw for ASU models based on 1 hr motoring per day"
Not sure what that means.

 

[JayGuevara]

Does seem very low to be true!

I got the info from here

Webasto Cruise CR49 Elegance Campervan & Caravan Compressor Fridge

Webasto Cruise CR49 Elegance Caravan & Campervan Fridge is available for next working day delivery (Like Waeco CR50)

www.jacksonsleisure.com

Indel Webasto: CRUISE 49 (Classic)

The small CRUISE refrigerators guarantee fresh food and cold drinks needing just a little space. Choose between Classic, INOX and Elegance style.

www.indelwebastomarine.com

 

[JayGuevara]

Interesting test results for the bigger CR115

 

[John Frum]

Interesting test results for the bigger CR115

158.9 watt hours per day is good... if accurate.

 

[John Frum]

BTW watt hours is the preferred metric.
Amp hours is only meaningful if you know the system voltage.

 

[tictag]

Is this correct?

Their datasheet seems to confirm this.

265Wh energy consumption over 24 hours means that it is drawing 11W on average over that period or 0.92A at 12V. But fridges are funny things because they usually operate with a low mark/space ratio i.e. on for 10 minutes, off for 50 minutes in any one hour. So it could actually be drawing 66W in operation.

My absorption fridge has a 120W heater but is only actually 'on' i.e. drawing 120W, for just minutes in each hour.

265Wh per 24-hour period is a good way of rating these, however, especially when considering what PV array would be required to replenish the energy use e.g. a 70W panel would easily power this continuously in Summer (70W x 80% x 5 hours = 280Wh)

Seems like a very efficient product to me.

 

[Cal]

BTW watt hours is the preferred metric.
Amp hours is only meaningful if you know the system voltage.

Watt hours is a convoluted unit. It's so much easier to deal in AH. The battery is rated in AH. Shunt measures amps. A simple arithmetic calculation. Not a problem to state system voltage.

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[tictag]

Watt hours is a convoluted unit. It's so much easier to deal in AH.

I do have to agree with @smoothJoey on this, AH measurements might be easier on the face of it but when you start adding in multiple options for battery system voltages, trying to match energy consumption to energy storage and array energy production, having everything in Watt-hours does make a lot of sense. I do agree, though, that AH is easier if the calculation task at hand is straightforward i.e. 'How long will this battery last if I I x, y, z.'

 

[Cal]

I do have to agree with @smoothJoey on this, AH measurements might be easier on the face of it but when you start adding in multiple options for battery system voltages, trying to match energy consumption to energy storage and array energy production, having everything in Watt-hours does make a lot of sense. I do agree, though, that AH is easier if the calculation task at hand is straightforward i.e. 'How long will this battery last if I I x, y, z.'

I don't see where there's multiple system voltages. Everything breaks down to battery current. That's the common denominator. Sure, there's an inverter and some dc/dc buck or boost regulators, but they are all taken care of by the battery shunt measurements.

You could be looking at errors when just looking at the watt rating for some electronic equipment. For example a tv might be rated at 35W. If you got a 1500W inverter and the only load is the tv, then inverter efficiency could be 50% (or lower). The battery is loaded now with 70W, not the expected 35W.

Bottom line, you want to know how much the battery is being loaded. So what are YOU going to do? The only accurate way is to measure battery current, and battery voltage. Multiply them together to get watts. That's convoluted. Measure current and you're done.

 

[tictag]

I don't see where there's multiple system voltages.

Most people choose a 12V battery system but there are times where 24V, 36V and even 48V systems are preferred e.g. for higher loads, resulting in smaller, cheaper cable.

Everything breaks down to battery current.

I wouldn't agree with this. Sure if you are just looking at instantaneous loads e.g. will my inverter power x?, or what should the gauge of my cable be? then current is king. But the moment you need to know things like e.g. will my system keep the lights on? Can I power my A/C during the Summer months? Will my array recharge my battery? I need to be off-grid for 7 days, what battery do I need? Then you're talking about energy, not power.

You never talk in AH units for solar panels. You rarely talk in AH units when doing an energy consumption audit. And it can be confusing to talk in AH units when considering whether parallel or series-connecting batteries is right for you e.g. 1 x 12V battery is 100AH, 2 x 12V batteries connected in series is 100AH - WTF!?

AH units make sense for very simple calculations, Wh units makes sense for everything else.

I always try to work stuff out in Wh units, keeps things simple, then, if I have to, convert to AH units if needs be.

But to each their own!

 

[John Frum]

I realise now that I actually prefer to read and write $a amps@$v volts instead of $w watts.
Watts alone without volts or amps doesn't tell the whole story.
I've changed my mind.

 

[Dhowman]

I do have to agree with @smoothJoey on this, AH measurements might be easier on the face of it but when you start adding in multiple options for battery system voltages, trying to match energy consumption to energy storage and array energy production, having everything in Watt-hours does make a lot of sense. I do agree, though, that AH is easier if the calculation task at hand is straightforward i.e. 'How long will this battery last if I I x, y, z.'

I concur here also. Give us power, not amps and no one needs to bother asking what your system voltage is, you don't need to provide it and we don't have to convert it in our heads if ours is powered differently than yours. When system planning that might have a 24V battery, 12V and 120V appliances, it doesn't matter where your appliance is in that system if you just spec everything in watts (or Wh). When talking about fridges, for example, that fridge could be powered directly from your 24V battery, your 12V distribution panel or plugged into your inverter. Same fridge, completely different amp draws but all the same wattage.

I realise now that I actually prefer to read and write $a amps@$v volts instead of $w watts.
Watts alone without volts or amps doesn't tell the whole story.
I've changed my mind.

Yeah, that's ok when talking about DC systems, but VA and W are 2 different things when talking about AC: VA is "apparent power" and W is "real power" ... two different specs.

 

[Cal]

I wouldn't agree with this.

But to each their own!

I likewise don't agree with your point of view.

Batteries are rated in AH.

Enough said!

 

[Cal]

When talking about fridges, for example, that fridge could be powered directly from your 24V battery, your 12V distribution panel or plugged into your inverter. Same fridge, completely different amp draws but all the same wattage.

I just gave an example (with tv) where the tv power rating doesn't mean much when connected to an inverter operating at 50% efficiency. If we have a 24V battery then you'll see 3 different currents whether the fridge is connected directly to battery, or to an inverter, or to a 12V to 24V regulator.

 

[JayGuevara]

Is it better to wire my two 275w panels in series to double the voltage or parallel?

I have an epever BN series 40 amp scc.

I think I remember will saying it's better to have higher voltage for effiency?

 

[mapguy525]

I am a little late to the party here but the CR 49 AC/DC model is rated at 340 watts/24hr with this "note"

*Note: Power consumption W/24 h in operation on 12 V with +5°C in the refrigeration space, ambient temperature +25°C according to the Standards ISO 15502:2005 and EN 153:2006.

Listed amperage will change with ambient temperature and unit door openings.

A good website to see various compressor DC and or AC/DC refrigeration models from several manufactures is Sure Marine. This is where the link originated:
https://www.suremarineservice.com/Galley/Cruise-Elegance/ISO-C049RSBAS71113AA.html