PROCESS, METHOD AND MAD­NESS

Eight fridges, thou­sands of high-tech record­ings and a wild card to ruf­fle a few feath­ers – it’s the ul­ti­mate fridge test.

4 x 4 Australia - - Gear -

WE’VE gath­ered eight of the most com­mon 12-volt fridges on the mar­ket in an at­tempt to find out which one reigns supreme. We’ve also thrown in a wild card – a fridge pur­chased by the au­thor back in 1990 – to see how ad­vanced the lat­est and great­est units re­ally are. The 26-year-old En­gel has kept things cool on a trip around Aus­tralia, served as a ‘house’ freezer in Dar­win, and it has since been used (and some­what abused) on count­less long and short-term camp­ing trips.

Will our well-trav­elled and much-used En­gel – com­plete with dents, rust and a dust-clogged com­pres­sor – be able to match it with the lat­est of­fer­ings?

To add a bucket-load of va­lid­ity to our test­ing, we’ve sourced a few high-tech gad­gets to prove a few im­pos­si­ble-toguess qual­i­ties of each fridge. We’ve pro­grammed tem­per­a­ture data recorders to store read­ings ev­ery 10 min­utes, which can then be graphed and over­laid with all other fridges, as well as am­bi­ent tem­per­a­ture record­ings. We also hooked up high-pre­ci­sion power anal­y­sers to keep track of power us­age, so we can re­gur­gi­tate av­er­age amp-hours used by each fridge.

WE wanted to repli­cate a real camp­ing en­vi­ron­ment, but there are some things you can’t con­trol in the bush. So we opted to con­duct the test in my non-nataac­cred­ited man­cave, com­plete with heaters, lights and 240-volt power.

We didn’t run the fridges on 240V; in­stead we used a 50-amp Pro­jecta IC5000 7-stage In­telli-charge bat­tery charger set to con­stant power sup­ply to keep a 125ah Cen­tury deep-cy­cle bat­tery charged.

This ‘power sup­ply’ mode ad­min­is­ters a float charge to the bat­tery, to en­sure ap­pro­pri­ate power lev­els are main­tained when run­ning ap­pli­ances. Plus it doesn’t run the risk of over­charg­ing the bat­tery.

The fridges were all wired into that one bat­tery, so they all had a com­pa­ra­ble 12-volt sup­ply with­out the worry of the bat­tery go­ing flat.

We sourced a tem­per­a­ture data record­ing kit to record in­ter­nal temps of each fridge ev­ery 10 min­utes, plus we used an ex­tra recorder to record am­bi­ent tem­per­a­tures ev­ery 10 min­utes.

Each fridge was packed with equal amounts of food and drinks: a loaf of bread, a two-litre orange juice bot­tle, eight cans of drink, four ap­ples, four or­anges, one packet of cho­co­late bis­cuits and a bag of salad leaves. The fridges were packed about two-thirds full to make the fridges work harder – given air tem­per­a­ture is harder to reg­u­late than solid (food and liq­uid) tem­per­a­tures.

DAY ONE: We packed the food and drinks into each fridge, which had been set at 3°C and had been run­ning for two days prior to load­ing. The only ex­cep­tion was the old En­gel, which has a sim­ple num­bered dial that was set at 2.5 (given my prior ex­pe­ri­ence us­ing it). Time would tell what tem­per­a­ture that set­ting would re­turn.

DAY TWO: Each fridge re­mained closed day and night to mon­i­tor the ef­fec­tive­ness of the com­pres­sors and the ac­cu­racy of the tem­per­a­ture set­tings dur­ing a mod­er­ately warm day and cold night. This gave us the op­por­tu­nity to graph the cool-down pe­ri­ods and es­tab­lish how sta­ble each fridge would op­er­ate with­out over­cool­ing or over­warm­ing the contents.

DAYS THREE AND FOUR: At mid­day each fridge door was opened for five min­utes. We then turned blow heaters on in the shed (not point­ing at the fridges) to raise the am­bi­ent tem­per­a­tures, as we wanted to have a go at repli­cat­ing the heat-sap­ping tem­per­a­tures of a scorch­ing Aussie sum­mer. That fi­nalised 100 hours of run-time over four and a bit days.

To test the ther­mal in­su­la­tion prop­er­ties of each fridge at the end of day four, we turned all the fridges off, left all the food in­side and left the lids closed to record how long each fridge would hold a de­cent tem­per­a­ture. This fi­nal test repli­cated a bat­tery go­ing flat and how long you have un­til food starts to per­ish.

DAY FIVE: After turn­ing all fridges off we waited for 24 hours to re­trieve the

tem­per­a­ture data recorders. To keep it all even, no lids were opened and no fridges were touched.

We did mea­sure in­stan­ta­neous cur­rent draw, but it’s pretty much use­less info so there was no point print­ing it. Some fridges draw a higher ini­tial cur­rent than oth­ers, but cy­cle on for shorter pe­ri­ods of time com­pared to some with lower in­stant record­ings that run for a longer pe­riod or cy­cle more often. Longterm power use is more im­por­tant but is in­fin­itely vari­able due to many fac­tors. Again, all was even, so this gives you an ideal base line to com­pare all fridges.

When study­ing the graphs and col­lated data we con­cen­trated on how well each fridge kept its in­ter­nal cabi­net tem­per­a­ture com­pared to the am­bi­ent temps, as well as how much power was con­sumed over the first 100 hours. That, com­bined with the fi­nal 24-hour power down – as well as the de­sign, man­u­fac­tur­ing fin­ish and price – all led to our fi­nal de­ci­sion.

All fridges were wired into a 125ah Cen­tury deep-cy­cle bat­tery, kept topped up with a Pro­jecta charger (right).

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