Thermoelectric Coolers: Four-Model Chilldown
Igloo cools fastest, Koolatron draws the least current, but for all-around marine use we'd go with the Adler/Barbour Tropicool.
The last time we tested thermoelectric coolers, back in December of 1996, we spent a fair amount of space describing the history and science of the Peltier Effect, the process by which these coolers work. (In a nutshell, when you send an electrical current through the joint between two dissimilar metals, heat will pass from one metal to the other. This was discovered by M. Peltier in 1834.)
As PS readers know, from having read many an article about compressor-driven refrigeration, making an icebox work is not about adding cold air to the space, but by continually removing heat from it. A Peltier Effect cooler removes heat from its insulated space by driving an electric current through those dissimilar metal partnerships (called thermocouples) set up in a series (called a thermopile), and pulling the warmth away from the thermopile and outside the cooler with a fan. It's simple, quiet, and has one moving part—the fan. It's also lightweight and portable—a cooler with a thermopile and fan weighs only marginally more than an empty cooler, and of course everything except the power cord is contained in the box itself.
Because the Peltier Effect can work both ways, these coolers can also act as warmers. In most cases you simply reverse the plug connection in order to warm the box.
Finally, they're cheap. Compare the prices in the accompanying chart to the cost of a new compressor-driven refrigeration system.
Of course there are drawbacks to thermoelectric coolers, too. First, they're quite power-hungry, most needing about 4.5 amps continuously. That'll draw your house battery down fast if you're not generating power to it. Second, they're not very well insulated, simply because their makers expect that you'll be supplying ample amounts of power to them. Third, they generally cannot cool their innards lower than about 40 degrees below the ambient temperature. This means (obviously) that they won't make ice if it's warmer than 72 degrees out. If it chillier than that, they can make ice, but very gradually. It's better to think of them as ice-preservers, not ice-makers. Fourth, they're stand-alone boxes, and big ones at that. So if you intend to use one on your boat, you'll need to think carefully about where you're going to put it and secure it, especially considering that you'll need to plug it in to a cigarette lighter adaptor or wire it directly to a circuit breaker. We've included dimensions of the units we tested in the chart on page 18.
What We Tested
In our '96 test, the Coleman Thermo II cooler bested the other three units tried. This time we tried the Coleman Powerchill 40-quart model. It was joined by the Igloo Kool Mate 32 (the same as last time), the Koolatron cooler from Canada (same as last time), and the Waeco-Adler/Barbour Tropicool Classic TC-32.
Amazingly, three of the four coolers arrived at our offices slightly damaged. The Coleman had a fist-sized dent in the lid. The shroud covering the Koolatron's thermopile and fan motor had a stress crack around its mounting screw. (We repaired it with glue.) The shroud inside the Igloo was completely detached and had to be snapped back in place, and there was also some scuffing or maybe roughness due to a poor mold release in the box lip directly above both handles. Only the Adler/Barbour unit arrived unscathed, possible because it was hand-delivered from only a couple of miles away. In any case, if you go to your local department store to buy one of these coolers, better inspect it before you leave the parking lot.
How We Tested
The accompanying chart shows the basic test procedures. Here are a few other notes.
We tested each unit under identical inside conditions, with the same indoor-outdoor thermometer. We used a 12-volt power supply (running at 13.8 volts) to power the units, and took electrical current measurements several times, starting about half an hour after each machine was turned on. We took decibel readings 12" from the fan. The thermometer probe was on a stiff wire, and care was taken to make sure it was suspended in mid-air near the middle of each cooler space.
We learned in our last test, and confirmed with this one, that an empty cooler will reach its lowest temperature within 2 to 3 hours of being started. We took temperatures at the 1-hour and 2-hour marks. After two hours we inserted a gallon of water warmed to exactly 100° F. Three hours later we took the temperature again, then left each cooler to run overnight. (With the ambient temperature steady at 70°, we were interested to see if any of the coolers would make ice while we were tossing and turning. None did.) The overnight runs lasted about 16 hours.
Finally, we bought a bunch of food and drink, and fitted that bunch into each cooler, just to see if and how it would pack. Here's the list of items:
2 six-packs of canned soda
1 six-pack bottled beer
1 quart milk
½ gallon juice
1 small Danish ham
1 package turkey breast
½ lb. cheddar cheese
½ lb. American cheese
1 stick butter
All four coolers held that load. The interior volume numbers on the chart would seem to indicate that the Igloo would be the most challenging to load, but we found the Adler/Barbour a bit more challenging. Obviously, this has mostly to do with interior volume, but also the shape of the space and the galley chief's packing skills. The Coleman had the most room to spare, which makes sense, because it has more volume.
Igloo Kool Mate 32
The Igloo recorded the best cooling performance of the four. It got down to the lowest empty temperature within two hours, and tied with the Koolatron after the overnight run. It has a very strong twist-lock latch (or twist-latch lock?) The lock on ours was quite a finger-bender to turn, but would be improved by a bit of Teflon lubricant. The box itself is nicely shaped, with rounded corners that won't bite into shins and knees. Handles are external, but flush.
We thought this was a good, solid cooler back in '96, and still think so. It demands the least power among all the units tested—by a full amp—and has a couple of other features that distinguish it from the others. The lid is split into two sections, with the Peltier thermopile and fan located in one section. The ability to open just half the lid at a time will help conserve cold air inside. There's a clever sliding latch that allows you to lock the box, or open one or both lids. The downside of the lid is that if you spill liquid on top of the cooler, it's likely to go right down into the fan. That lid can also drop with quite a bang. The Koolatron shares the smallest footprint size with the Adler/Barbour Tropicool.
Coleman Power Chill
This 40-quart unit was the biggest of the four coolers, the quietest, and the least expensive (at least at press time). It also performed well in the cooling test, despite the fact that it had more volume and therefore more heat to evacuate.
The indented hand grips are a good feature, and the lid is enclosed on both ends by the raised lips of the box, which will prevent things from snagging it. Unfortunately, the lid has no locking mechanism at all, and there's no obvious way of retrofitting one without puncturing the box. The way to go would probably be with Velcro straps, either making sure the strap ends are well-adhered, or sewing the hook-and-loop terminals to some webbing and running the webbing right around the box. Velcro is noisy, though, when you're trying to sneak a midnight snack.
The Tropicool is made by the German company, Waeco, (actually, it's manufactured in China) but is sold and supported in the U.S. by Adler/Barbour, a company familiar to most sailors for its excellent marine refrigeration systems. This cooler appears to be of somewhat better construction than the others—not necessarily more robust in its plastic parts, but the parts are well-fitted and aligned, and the cooler seems more "seamless." Its lifting handles lie flush against the box, and it has decent hinges and a good positive latch. While the other three units are activated when plugged in (and changed from cooling device to warming device by reversing the power cord) the Tropicool has buttons for "Cold," "Off," and "Hot," and a sliding control that lets you adjust how hot or how cold.
The cooling performance of these units is so close that it doesn't make sense to judge them on that criterion alone. If we did, however, the Igloo would win.
As for electrical current demand, the Koolatron has a significant edge, and this would be of concern on boats with smaller battery banks or lesser charging capacity. It's a bit slower than the rest to cool, but ends up with the coolest.
The Coleman, if fitted with a retaining strap for the lid, would make a good choice at the price. But remember, this is a bruiser in size. It would be nice if Coleman still made a cooler in a 32-quart size, but the only ones currently listed for sale by Coleman are this 40-quart jumbo and a 16-quart version with a shoulder strap.
If we had to pick a cooler for ourselves (and sometimes that's what these evaluations come down to), we'd go with the Adler/Barbour Tropicool. It's a bit smaller to stuff with food, but also a bit easier to stow (same footprint as the Koolatron, but a bit taller). It did well in the cooling sprint (although, according to the chart, it was still chewing on that gallon of 100-degree water the morning after). The sliding temperature adjustment would be quite valuable for people sailing in climates with wide variations in the weather. And while the cooler seems well-built, if we needed customer support, Adler/Barbour's track record in the marine industry is stellar.
For most sailors, the most important shopping points will be outside dimensions and power requirements. Given the fact that all of these boxes draw lots of power and have poor insulation, we can't see that anyone with a well-insulated icebox and a working refrigeration system would want to trade it in for one of these. On the other hand, if you have no compressor-driven system, or need to replace a broken one, a Peltier box might make sense in several ways. And, as we noted in a PS Advisor in the April 15 issue, it's possible to retrofit your existing icebox with a Peltier device. Consult www.peltier-info.com/manufacturers.html for a list of companies that make thermoelectric modules.