Being able to keep foodstuffs and beverages cold on a safari is a real luxury. Once you have used a fridge or freezer on safari you will never be able to do without one. There are three types: Compressor, heat-exchange and thermoelectric cooler.
Most compressor freezers run on both 12 and 220-volts. Because they are controlled by an adjustable thermostat, current draw is more efficient because it maintains the fridge and its contents at a constant temperature. The colder the setting, the higher the current consumption both in attaining the desired temperature and maintaining it. Space utilization varies from efficient to down right bulky.
Thermoelectric coolers run on the Peltier principle that if a current is passed through a special metal element it becomes cold and if the current direction is reversed the element gets hot. So thermoelectric can also be used to warm up food. Apart from a small fan, thermoelectric fridges are solid state and very quiet but will not freeze and are slow to cool when compared to compressor fridges.
They run off 12-volts and are not thermostat-controlled, meaning that they are inefficient in terms of current consumption. Get one if you will be satisfied with; only running it when the engine is running, drinks that are cool and not cold and no chance of freezing anything.
Heat Exchange Freezers
Powered by LP gas and by 12-volts and 220-volts, heat-exchange fridges are inefficient when run off 12-volts, fairly efficient off 220-volts and highly efficient running on gas or paraffin.
The versatility of power source means that in situations where they remain in one location for a long period when battery charging is not possible or practical, they keep working. In a vehicle they must, for safety reasons, work off 12-volts. However, when in a moving vehicle or trailer under electric power they do lose efficiency and depending on outside influences, may not freeze. When set up in a fixed location they must be leveled, the flame centered, the regulator set and a yearly cleaning. They have no thermostat so when working off 12-volts the current draw, which averages 7-8 amps is not controlled, I.e. it runs 24-hours a day. This makes them hugely inefficient on 12-volts.
Selecting a compressor fridge/freezer
Engel, Weaco and National Luna currently make the best portable fridge/freezers anywhere. Minus-40 also make a good product but they are all so unnecessarily large they are for the most part impractical for use inside a vehicle. Some other makes are appallingly inefficient and don’t perform even to their own specifications under real hot, humid conditions inside a vehicle.
My advice is dismiss them and look for solid word-of-mouth recommendations. Secondly, as mentioned in chapter-3, I believe that it’s more about how the current is put back into the battery than how much is taken out.
Because 12-volt compressor freezers are by far the favorite for the 4×4 operator, I will confine my detailed discussions to this type.
Beware of false current draw claims
It is so easy for freezer manufacturers to claim exceptionally low current consumption for their products and tout theirs as better than the competitor’s. This is how it is done, without lying: Make a statement like: Current draw 2,5 amps @ 12 – 24 volts. Such a freezer is likely to draw 3.5 amps @ 12 volts, 2.5 amps @ 18 volts and 2 amps @ 24 volts. Because a healthy, charged battery will operate between 12,5 and 13,8 volts, in this way the figures published look better than they really are when the freezer is used out in the field.
FRIDGE/FREEZER BUYERS’ GUIDE
Most of my testing has meant taking each of these freezers on an extended trip where I used them as most buyers would – in the bush. These are impressions and the data has not been gathered using scientific controls.
ENGEL 40L fridge/freezer:
• Best current draw ±2,5 amps @ 12.8 volts. Excellent.
• Insulation is second thinnest.
• Easy to operate single knob for adjustment. Can be knocked, i.e. adjusted ‘accidentally’.
• Time to freeze from turn-on: I would say extremely fast.
• Removable lid.
• One large basket with no dividers. (The least practical of all but the Pro-Cool)
• No internal light.
• Compact and good space utilization. Not as heavy as the Luna.
• Excellent record of reliability, spare parts supply and service backup.
• Priced average. Excellent quality. Reliable. One of the best
ARB 47L fridge/freezer:
• Best current draw ±3,3 amps @ 12.8 volts.
• Insulation is above average. Very quiet operation.
• Easy to operate electronic keypad. Adjustable cut-off voltage. Cannot be adjusted ‘accidentally’. The best control panel of all.
• Time to freeze from turn-on: I would say slower than average.
• Removable lid.
• One large basket with one divider – very practical
• Internal LED light.
• Compact and good space utilization. Not as heavy as the Engel.
• The new kid on the block, built by ARB who have never made a bad product. This one could eclipse the Engel. Spare parts supply and service backup by 4×4 mega World
• Priced average. Excellent quality. 47L capacity. May be better than Engel
NATIONAL LUNA 40L fridge/freezer:
• Best current draw ± 3,4 amps @ 12.8 volts.
• Thickest and therefore probably the best insulation of the five.
• A little awkward to adjust settings (Needed to consult book to remind me how to do it) Cannot be readjusted ‘accidentally’.
• Time to freeze from turn-on: I would say maybe the fastest.
• Not only a removable lid, it can be reversed. Nice!
• Two baskets. Practical size and shape.
• Internal LED light.
• Less compact, and heaviest of the five.
• Hella-plug external power supply. Nice!
• Excellent record of reliability, spare parts supply and service backup. Priced a little above the others. I am not sure if it warrants the higher price but excellent quality.
WEACO 40L fridge/freezer:
• Best current draw ±4.0 amps @ 12.8 volts.
• Thinnest and therefore probably the poorest insulation of the three.
• Very easy to adjust settings. Unlikely to be readjusted ‘accidentally’.
• Time to freeze from turn-on: not as fast as the others.
• Not only a removable lid, it can be reversed.
• One basket with divider. Practical size and shape.
• Internal light, cleverly designed and practical.
• Most compact; the smallest and by far the lightest of the five.
• Imported by Outdoor Warehouse. Weaco has earned itself an excellent reliability record. The least expensive of the five, good value, and made chiefly of plastic so does not feel as well made as the others.
PRO-COOL/CAMPMASTER 45L fridge/freezer:
• Best current draw ±2.8 amps @ 12.8 volts. Excellent.
• Medium insulation.
• Fairly easy to adjust settings. Unlikely to be readjusted ‘accidentally’ but eco-switch flimsy and prone to damage.
• Time to freeze from turn-on: I would say fastest of all. On the ECO setting, may never freeze, so should not be used at start-up.
• No removable lid. No light.
• One basket, no divider. Not very practical. Too low for a 2L bottle.
• Cannot remove the power cable – annoying.
• Compact; about the same size at the Nat Luna, but extra .5L cap.
• Made in South Africa. Sold by Makro and Game, on the market for an insufficient period to record dependable reliability statistics. Among the least expensive of the five, but build quality is by far the poorest.
Additional ideas when selecting a compressor fridge/freezer:
• Compact and efficient space utilization because space in a vehicle is always at a premium.
• Stainless steel looks better in the shop but deteriorates rapidly and before long looks shabby in the vehicle. Stainless steel is a particularly poor insulator so a stainless fridge will be less efficient.
• Buy new. Old designs are far less efficient as new technologies have improved designs significantly over the past five years.
• In the confines of a vehicle, a removable lid is a real bonus.
• Internal lighting is nice but not essential.
• Low-voltage cut-out is essential and prevents a battery voltage from dropping to a level which could cause damage. Even a deep-cycle battery can be damaged in this way.
• Tie-down handles ensure that the unit can be well secured which is essential for travel in rough country. To prevent damage to the fridge, it must be secured.
• A slide out tray, on which to bolt the freezer, is really worthwhile.
Poor current flow caused by a combination of cheap connectors
and thin cabling is the most common cause of problems with freezer installations. When the compressor starts up, the current draw, albeit only for a second or two, can soar to 15 amps. Use the best quality connectors you can find.
When calculating the cable core thickness required, divide the length by 1000. E.g., if the cable length is 3 metres (3000mm) then the minimum cable core thickness is 3mm and if the length is 4 metres then 4mm cable is required, and so on. This will ensure adequate current flow along the length of cable, no matter how long it is.
RUNNING VEHICLE FRIDGES
To prevent over-discharge of the vehicle’s battery when the freezer runs at night it is essential to have a second battery and a charging system to split the two batteries. See chapter-3.
Calculating electric current draw
Because compressor fridges are thermostat controlled, current draw is as much dependent on the thermostat setting, quality of insulation, outside temperature and how frequently the fridge is opened as it is on the compressor installed and the electronics governing them. The quality of the cables and fittings also has a marked affect on fridge performance and current draw.
Preparation: (particularly important for heat-exchange types)
• Do not remove the special heat-sensitive fuse on Engel Freezers.
• If practical, cool down everything in your household fridge before packing the vehicle freezer.
• Remove the plastic cling wrap around canned beverages, as the plastic will inhibit air flow and reduce cooling efficiency.
• Liquid is better stored in metal containers than plastic.
• Over-filling the freezer will have a detrimental effect on efficiency.
• Keep the lid tightly closed to prevent air escaping. An air-tight lid has a huge affect on fridge performance.
• By keeping the amount of time the freezer is opened limited, the freezer will consume less current and the contents have a better chance of remaining frozen.
I do not advise fitting freezers or batteries in a trailer because:
• Current loss occurs along the long cable and plug.
• If a battery is in the trailer do not charge it via the tow hitch electrical socket. A separate socket with a minimum of 6mm core cable is needed or the battery will never receive a proper charge.
• When you go on a game drive the battery will not be recharged, wasting valuable engine charging time.
• The contents of a trailer are shaken about far more than those in a vehicle. Freezers that ride in trailers over long periods can suffer ruptured piping due to vibration.