01.Keeping cool on the move with your portable fridge
So you’re looking for a fridge that can run from your car battery as well as via a normal electricity connection?
You might even be after a model that can run off LP gas, or perhaps you just want to keep drinks cool while you’re travelling without messing about with ice or freezer bricks.
- When we tested back in 2003, we concluded that compressor models are probably the best option for most people. Most people who responded to our request for experiences with a portable fridge owned a compressor model, and most were happy with it.
- For short trips you’re probably just as well off using a cooler with ice bricks as the thermoelectric models on test – we found some don’t stay cool enough to store food, especially when the external temperature is warm.
There are three types of portable fridge to choose from with big differences between them:
You need to know what you’ll use the fridge for to choose the right type.
Please note: this information was current as of March 2009 but is still a useful guide to today's market.
What to look for
Type: If you want to be able to run the fridge on gas, you’ll need an absorption model. If you only need to run it off the car battery or electricity, a compressor or maybe a thermoelectric model might suit your needs — see the scenarios to find out which. If you choose a compressor model and want to be able to operate it from 240 V, check whether it comes with an adaptor or you have to buy it as an extra.
Compartments: Think about what you’re likely to put in the fridge, and whether you need a fridge or freezer or a model that can be both at the same time.
Size: The fridge needs to fit in your car with enough space around it for ventilation and still leave room for you bags and so on. Check the storage volume and whether it’ll hold all you’re likely to want to put in it. If you’ll need to move it around, check how much its weight will add to that of the load inside.
Temperature zones and evaporator position: Check the location of the evaporator or cooling surface, as any air above it is likely to be warmer. Read the instructions to see if there are different temperature zones or compartments.
Battery drain: If you’re likely to run the fridge often when your battery isn’t being charged, consider how much current it’ll draw. Five amps is quite high, one amp quite low. Also consider inbuilt battery protection if you’ll be using the main car battery to run the fridge — look for a model that cuts out and in again at a fairly high voltage to prevent the battery going flat. Alternatively, run the fridge off a second battery. Thermal covers are also available for extra insulation, which may help conserve battery power.
Off-road use: Make sure the manufacturer recommends the product for this use, and that it has good tie-down points and can handle hills. You could also consider shock-minimisation options for the fridge, such as a foam base for it to sit on.
Controls: Check how easy they are to set initially, and to adjust as conditions change in order to maintain the right temperature.
Baskets: Removable baskets may be easier to use than one deep compartment that you have to reach into and search for things.
These models operate in the same way as your fridge at home. They run on a 12 V battery or from 240 V AC mains electricity, usually by using an adaptor. We found few that come equipped to run from mains or battery - for some you need to buy an AC adaptor.
On the whole, the compressor models worked better than the thermoelectric or absorption ones. They stay cold under a wide range of ambient temperatures, and are much less of a drain on a car battery during normal running.
One problem we found is setting the temperature and maintaining it once the ambient temperature changes - food can freeze or become too warm if you don’t change it.
The Marshall family like to hit the road as often as they can and find a spot to pitch their tent. They sometimes stay in caravan parks or camping grounds with powered sites, but not always, so they’ve set their car up with a dual battery system and wired a compressor fridge into the second battery, which provides power to the fridge without causing car-starting hassles. George is also a keen fisherman and uses the fridge to store his bait — and hopefully the big haul from his fishing trips.
If you’re keen to connect to gas, an absorption model is your only option. This style of fridge has been around for many years; it doesn’t have a motor but relies on the cooling effect of a liquid (in this case ammonia) when it evaporates into a gas. For this it needs to be level and to have a heat source, which can be from a car battery, mains electricity or LP gas. Being able to use gas as the power source makes it handy for camping for prolonged periods in more remote locations.
The Princes are serious campers, who like nothing better than to spend time every so often in fairly remote locations. They find an absorption fridge best suits their needs — they get everything cold first on 240 V at home, then run the fridge/freezer off the car battery while getting to their destination, and then off LP gas once there. If they’re travelling on rough and hilly roads it doesn’t work very well, but it’s better than nothing, and it works well once they’ve stopped and have set it up level.
A thermoelectric system (very basically) produces heat or cold at a junction of dissimilar metal conductors where a current is flowing. However, ‘fridge’ would be a misnomer for this type of portable cooler/warmer, and they’re certainly not freezers - they’re really designed for short-term refrigeration or keeping warm. While they generally have a limited cooling ability, they’re still a substantial drain on the car battery (almost 5 amps) - disconnect them when you turn off your engine. They’re quite noisy, and are about the size of a small insulated cooler.
When we tested back in 2003, we found none of them maintained a temperature that’s adequate to store hot food safely (tested in an ambient temperature of 10°C).
As for their cooling abilities, some were unable to cool to an adequate temperature once the ambient temperature got to about 25°C or so, which isn’t unusual inside a car even in winter. In summer, when you’re more likely to use a cooler in the car, the temperature will be much hotter, so an insulated cooler with ice or ice bricks may in fact be more effective for a few hours at least. (Don’t be tempted to add ice to your thermoelectric cooler - manufacturers warn against it.)
The Marriott family spend their weekends driving from one sports ground to the next, following the sporting endeavours of their three children, and they find a thermoelectric fridge suits their needs. They live in a temperate area and like to have cool water in the car for the kids to drink. They also live 20 minutes out of town and like the convenience of storing their milk and other perishables in the fridge for the trip from the shop to home.