Current draw and insulation of portable fridges

[troppo]

After reviewing literature on small compressor fridge/freeezers, I am wondering about the efficiency or otherwise of the smaller ones. Do you have any thoughts about it?

I am considering purchasing a small portable compressor fridge/freezer for my little boat. Rimfire has no inbuilt ice-box, I have used a 55 litre camping one but it does not fit very well and with no nearby shops to where I will sail, replenishing ice is a problem. But the small fridges do not seem efficient.

Using Waeco as an example, average useage:
WAECO mobile solutions

CF18 (18 l): 1.2 A/Hrs [from some forum member who emailed Waeco]
CF 25 (23 l): .84 A/Hrs [from Waeco website, same as all below]
CF35AC (31 l): .85 A/Hrs
CF40AC (37 l): .87 A/Hrs
CF50AC (49 l): .86 A/Hrs


The 18 litre fridge uses approx 50% more power than the 49 litre one. That may be because the smaller ones are made with a priority on portability, thus having less insulation. It is a puzzle but the implication for me is that if the consumption figures are correct, I am saving no power by going for the smallest one. I am bettter off going for the largest one which physically fits the space for it. That is, does not overhang the seat it will live on and the lid can be opened fully without hitting anything. What do you reckon?

Oh, I guess I could increase insulation on a small one, those optional covers help with that, but that seems a bit like closing the gate after the horse has bolted.

[anjou]

A larger one with a few ice packs inside will be more efficient than the smaller one which has less insulation and less thermal mass

[troppo]

Thanks Anjou. Seems crazy to try and save power and space if the small ones are not as efficient.

[Fishspearit]

I used a Waeco, I believe it was the 40, and it used about 4 amps on 12VDC when running, and as long as it was full and cooled down it ran about 40% of the time, so about 40 Amp hours a day even in the tropics. Capable of freezing, but a lot more efficient when used as a refrigerator. Overall very happy with it, we had it in addition to a built in Adler Barbour fridge, but as an alternative to the built in fridge I think it's a great option.

[Pete7]

Troppo, we have the little CF18 in addition to a fridge on board. I haven't measured the Ah it needs, but it doesn't run very often so the quote figures look about right. You could be right about the smaller fridges having less insulation to make the unit more portable. The good news is they do a silver quilted blanket to go over the top to increase the insulation.

Good little fridges, we take ours to the beach with the food in it and charge it up on the way to the boat with the car lead. The only bad thing about the CF18 is they cost the same as a full size domestic home fridge freezer this side of the pond. Oh and as Firshspearit points out they can freeze down. Froze me sandwiches and coke the first time I used it. Finally you must use big heavy duty cables to wire them in. Cheap cigarette sockets and plugs won't cut it.

Pete

[malovich]

A smaller fridge will have more surface area per volume than a larger fridge, A larger fridge will be more efficient per liter than a smaller one, I have no idea why the tiniest fridge has the worst power usage aside from the previously mentioned design considerations.

[barnakiel]

Originally Posted by troppo

CF18 (18 l): 1.2 A/Hrs [from some forum member who emailed Waeco]
CF 25 (23 l): .84 A/Hrs [from Waeco website, same as all below]
CF35AC (31 l): .85 A/Hrs
CF40AC (37 l): .87 A/Hrs
CF50AC (49 l): .86 A/Hrs

I have noticed the duty cycle is different for the smaller vs. the bigger models too. So, the numbers you quote may also reflect this.

A friend has a 40 (or 45) model and this one uses WAY more energy than what stands in WAECO leaflet.

b.