Volts With Vince - Keeping It Cool Inside
05 JULY | PRODUCT NEWS
In my series of Volts with Vince we’ve canvassed batteries and how to look after them, including the new kid on the block, Lithium-ion, as a way to increase storage and shed some kilos. We’ve also looked at the best ways and means of keeping the power up to them.
Solar is something I find particularly fascinating in performing that task, so with the energy storage and its generation now under our belts, I reckon it’s about time we used what’s in the bank, and I can think of no finer use of power than to feed me and to keep my drinks cold!
So, there are fridges, and there are fridges and brands you may be familiar with include ARB, Engel, Waeco, Trailblaza, Bushman and Evakool and others you’ll likely be familiar with like National Luna, a premium brand we stock in store at Battery World.
Now, I do not intend this article to be an exhaustive listing of fridge brands and what makes one better than another, but I will provide a basic description of how the refrigeration process works and a rundown of the do’s and don’ts when using a 12-volt fridge so that you can maximise your 12-volt system’s staying power.
A fridge will likely be the most demanding of all the appliances you hook up to your 12-volt system and the one most likely to have you hovering around your voltmeter if you’re free-camping with limited reserves of energy, so you need to have it set up as best you can.
When I mentioned to David that I was going to write about fridges in this issue, he chimed in with his two-bobs worth. He comes into my Battery World store when he adds a new camper trailer to his fleet, to select the most efficient batteries are refrigeration will be the top priority for his hirers. In the hire game reliability and simplicity are essential, and he also made the point that the type of insulation used in the fridge design has a significant bearing on the efficiency of the system.
His camper fleet is made by Kimberley Kampers, and a trait of the Kimberley brand was to use a eutectic fridge system. The beauty with eutectics is that one the fridge cabinet is cold, by freezing a fluid between the inner and outer walls, the fridge will barely need any charge to stay at the desired temperature and stay there for a long time. That style of ‘phase-change’ or temperature swap was likely the best, but sadly, eutectics aren’t common anymore.
The closest in performance-terms to the eutectic fridges I’ve seen are those made by a South African company called National Luna, pictures of which have been used for this article. While National Luna isn’t using an ice-bank cold-store, they do use a very dense insulating material that is the essence of keeping the ambient temperature at bay.
The insulating foam is injected into the cabinet void at high pressure and fills every nook and cranny, and that density ensures the cabinet stays cold and for longer. With wall thickness between 42mm and 60mm, the heat is going to take a lot longer to affect the cabinet temperature.
National Luna says that while they offer a padded bag for their fridges, it’s only to protect the looks, not for additional thermal insulation.
Fridges today typically rely on a cabinet body using a combination of a metal or plastic skin stuffed with styrene foam or insulwool (fibreglass) materials that really benefit from having an extra layer added to them.
Not only do padded insulating bags add more thermal efficiency by slowing the ambient temperature of the day and its creep into the fridge’s cabinet, but they also afford a modicum of protection in preventing dings and scratches.
This style of fridge will work longer hours and draw more current. That’s okay if you’re on the move and your alternator can keep trickling the charge, or you’re equipped with a dual-battery set-up, but it’s not so hot if you’re in the one spot for days on end without the benefit of solar panels or a generator.
Fridges use a compressor (brands like Danfoss and Sawafuji are common) which is the heart of the system. It circulates refrigerant throughout the unit by adding pressure to the warm part of the circuit, squeezing the once fluid refrigerant, and transforming it into a gas.
That process generates heat and the now how refrigerant gas is cooled by passing it through a condenser, a process that turns back into a liquid. From there is ends up in the evaporator and if you’ve ever looked at the inside of an ARB or Engel fridge you will have seen ribs on a metal plate that are cold to the touch and do the chilling business. As the cold passes into the fridge contents and the refrigerant starts to warm the cycle starts once more. That’s a very simplified version of the heat exchange process.
That process also relies on the 12-volt supply being robust. Running a power feed from the vehicle’s battery to the fridge must be designed with voltage-drop in mind. If your cable run uses wire that is too thin to deliver the fridge’s power requirements, it may never start, only work intermittently, or the cable will get hot enough to start a fire.
Vince reckons it pays to keep your fridge full, make sure there is plenty of breathing space around the fridge, avoid overheating your interior and resist turning it down to near freezing cold. Do all that, and it’ll work a treat.
Here are my four main recommendations for running a fridge, so that it makes the most of every AMP that’s on offer.
1. Keep the bugger full
A half or third-full fridge will make the compressor work harder and longer because it’s trying to cool down that void. If the fridge is full or at least close to it, it’ll help keep the temperatures more stable as the chilled contents act like a big ice block. When you want that next beer, it’ll be ready for you, and it’ll be cold, which is important. Get into the habit of replacing each item you remove to consume with something new, like beer or wine.
2. Near-freezing is too cold.
Setting the temperature on the thermostat to 0oC or lower in the quest to keep the contents super-chilled will work the fridge harder. How much harder? Try two to four times. It’s likely your fridge at home is set around 3oC so give that a try on the car fridge too.
3. Give it some breathing space.
There’s a thing called a condenser inside that fridge cabinet, and its job is to dissipate heat, which is part and parcel of the exchange of temperatures that creates cool air on the inside of your fridge. If the vents in the outside of the cabinet are covered, that heat can’t escape, and the fridge will work harder, use more power and still not cool its contents effectively. Leave enough space around your fridge for it to get the air it needs to work efficiently.
4. Global warming in your wagon.
A typical 4x4 wagon has acres of glass, which is great for visibility but bad for heating things up in the middle of the day. With all the doors closed and the windows tight there’s no fresh air movement and nowhere for the hot air within the vehicle to escape. That means the temperature soars and your fridge starts working real hard. If you’re parked up, choose a shady location, crack open some windows or even open some doors to get the air flowing.
For the ‘slow’ campers out there, you know the ones that have the luxury of plenty of time to spend in one location; you’ll be employing all of these tricks to stretch the charge your batteries are holding to the max. Of course, a well set up site will likely have the benefit of solar panels (make sure you keep the face of the panels pointed at the sun) or perhaps a generator (provided you’ve got no neighbours), so topping up the reserves might nearly be endless.
When all is said and done, taking some simple steps to reduce your fridge’s power consumption makes a significant difference when you’re in a remote location and looking to maximise your 12-volt system’s capacity.