Car Fridges

Submitted: Wednesday, Jan 15, 2003 at 15:46
ThreadID: 2974 Views:2381 Replies:3 FollowUps:9
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Can anyone enlighten me on the subject of power use of car fridges. As already stated in this column various fridges use various power and this seems to be because of the insulation/ thickness of the cabinet. According to tests/ manafacturers specs. I have come up with the following sums. At 35c a Trailblaza uses 32amp, Engle - 38amp, Waeco - 46amp and Evakool - 45amp.This is if the fridge is running at a constant +2deg. If I have two 120 d.c Batteries backed up by a Christie gen set, why would I not go for the cheaper Fridge as they all seen to be of good quality these days.
On another note has anyone used the newer Christie gen set. They claim that they put out 110amp and are as quiet as the Honda EU10i. They are only a fraction larger in size than their smaller cousin ( 55amp) weigh only 17kg, and cost $1234.
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Reply By: OziExplorer - Wednesday, Jan 15, 2003 at 17:06

Wednesday, Jan 15, 2003 at 17:06
Nobby, first of all you have to compare apples with apples, not apples to melons.
Your figures on the Trailblaza are most definitely incorrect. 42 amps is the mark for that fridge.
In the rest of the figures you are quoting, you are not quoting the size of the fridges that go with those figures.
The Engel was only 40 litres
The evaKool was 50 litres
The Weaco was 40 litres
The Trailblaza was 40 litres
Now if you work those figures back to litres for power consumed the evaKool works out the best.
No reason at all you should not go for the cheaper fridge, as all the Danfoss powered fridges are good. If you are going on bad roads constantly, the evaKool is the only fridge on the market that uses the IndelB suspesion system, which Danfoss have on their website as being the best suspension system available for their compressors. That is the system used on all the NATO fridges with Danfoss compressors.
At least with a Danfoss powered fridge you can get it repaired anywhere if necessary and is unusual to need repairs, and they are easily and cost effectively repaired unlike Engel.

Charging deep cycle batteries with an alternator of that capacity will ensure the batteries are not going to have a very long life. You would be far better off buying the small Honda GX100 motor for $460 and getting a Lucas generator and three barrel regulator fully rebuilt from your local auto electrician for about $160 and hooking it up to the motor. You can also put a small relay on the system to automatically cut the motor off as soon as the batteries were fully charged. Noise with a C20 generator is not going to be much of an issue as you would only need to run the Honda motor at around 1/3 throttle. Charging batteries is far superior to charging with an alternator, and ensures the batteries get fully charged. Those Christie built generating sets are good for people with heaps of money that can afford to regularly replace their batteries, or just use them once or twice to start earthmoving gear in the field. They are most definitely not good for charging deep cycle batteries on an ongoing basis, and are unlikely to charge the batteries to full capacity. A generator for example will charge at 20 amps continuously till the battery is *fully* and properly charged. An alternator will start at say 50 amps, as it is totally voltage dependent on what amperage it will charge at, and quickly reduce down to say 10 to 15 amps while the motor is still screaming its head off, and as the battery gets up, it drops down to say 5 amps and the battery is still not fully charged. Where as a generator stays at the 20 amps all the time it is charging the battery and only drops down once the battery is charged. If you take a 55 amp alternator and a 20 amp generator, there will be virtually no difference in the amount of time taken to charge the battery. But of course the generator will have charged the battery 100% where as the alternator at best will have charged it 90%. Now 10% may not sound like much difference, but in practices that is probably 25%+ of the battery capacity. Unfortunatly everything in the auto electrical field is not black and white, you need to know how these devices work and function.

Do you really need two batteries. One battery should be more than sufficient for 2 days running including lights. More batteries always equal more problems.

Have you considered solar panels instead of a gen set. You can do solar panels for the same price as a Christie gen set and never have to bother with fuel, servicing or replacment cost as solar panels have 25 year warranty.

AnswerID: 11339

Follow Up By: Ray - Thursday, Jan 16, 2003 at 14:34

Thursday, Jan 16, 2003 at 14:34

I have run my Christie gen set many times and tested battery capacity and it does fully charge though yes of course it takes time as it is voltage regulated. Charging deep cycle batteries on this system should be no different to a standard battery charger, the Christie unit is simply left on low charge. The max output of the gen set, battery charger or solar pannel is of little relevance unless the resistance of the battery and wires etc is very low, at which point the battery may accept max charge. A deep cycle battery has higher resistance so whether you use a 55 amp charger or 500 amp it makes little difference as the battery limits the current supply though resistance. Supply is regulated by the resistance, incorrect voltages destroy batteries!! This and other fundemental laws make me wonder how a generator will be any different to an altenator. ie as the resistance increases either the current flow reduces or the voltage must increase. If the voltage increases beyond about 15.2volts for a flooded lead acid you will reduce the life of the battery. So how does a generator continue to output max current without increasing the voltage beyond safe levels of the battery?

FollowupID: 6293

Follow Up By: Oziexplorer - Thursday, Jan 16, 2003 at 17:18

Thursday, Jan 16, 2003 at 17:18
Ray, the way an alternator charges has no relevence whatsoever to a generator. A generator will always be a superior battery charger to an alternator and always will be, unless you use electronics to overcome the deficiences of an alternator.
An alternator output as you have stated is 100% voltage related, not a generator. For example a Lucas C20 generator with a 3 barrel regulator will charge at a continuous 22amps till the battery is fully charged and then drop down to a small float charge. Sure, you can buy smart three step regulators for alternators, but these are expensive and still do not as good as a three step generator mechanical tempreture compensated regulator. If you check alternators on motor vehicles, it is not unusual for the batteries to only being charged to 80% capacity. For motor vehicles if you are just charging the starting battery an alternator is fine and good for the job, but it is when you come to charge deep cycle batteries that a generator sure comes into its own in every way. Find a well experienced auto electrician in your area who will explain to you how a three barrel regulator works and how the generator charges. You need to find a person probably around the 50 mark.
The new motor vehicle 42vDC systems will more than likely have a generator fitted as standard, so far, not an alternator in site in the scheme of things!
If you would like to buy a ticket to go to Manchester, UK for the 29th and 30th of January 2003, you can be as informed as I will be on the new design of 36 to 42v vehicle systems and vehicle charging systems.
Here is the information you will want. I may even be able to get you a discount! (warning is a PDF file)
FollowupID: 6296

Reply By: Member - NOBBY - Wednesday, Jan 15, 2003 at 19:40

Wednesday, Jan 15, 2003 at 19:40
Ozi.. Thanks for the reply. My Trailblaza figures are taken from their spec. sheet on a 60 litre model. They claim the following:
22 amp/24hrs @ 25deg
32 amp/24hrs @ 35deg
46 amp/24hrs @ 45deg.
They might have a slippery grip on the truth!!!. Anyhow it looks like the Evakool will get the dollars. The reason for the twin batteries is that they are already on the CampOmatic that I have just purchased. I will check your theory ( and I'm sure it is right after reading your answers in the past) with my Auto Elect. and will probably end up buying a Honda EU10i, certainly not because I'm flush with $, but because I don't want any hassels when travelling, and Honda put out a good and reliable product.
AnswerID: 11343

Follow Up By: Oziexplorer - Wednesday, Jan 15, 2003 at 20:06

Wednesday, Jan 15, 2003 at 20:06
Nobby what about solar panels? A once off purchase with no noise or cost to run. I just *LOVE* my solar panels and have more power than I know what to do with. I even have the luxery of a 55 watt halogen flood light on the back of the vehicle to light up the campsite at night if I want.

Well, the Trailblaza figures are most definitely rubbery. Reason, only last week I put my data logger on a 40 litre Trailblaza for a week as I was keen to know if they were any better power consumption than others. Sure was not controlled in tempreture, but we did average the tempreture figures over a 24 hour period for three separate days.

I am exactly the same. I also don't like hassels and like to spend the money once and do the job properly once. I can go away always in confidence with the minimum of tools as the chances of a breakdown are very low. I have a vehicle maintainence regime which some may think expensive, but my vehicles last a long time completely trouble free. I don't have radiator replacements, alternator or starter repairs or those type of major expenses or breakdowns.
FollowupID: 6271

Follow Up By: Member - Robert - Thursday, Jan 16, 2003 at 23:12

Thursday, Jan 16, 2003 at 23:12
hey ozi, why don't you tell us about your solar panel setup - brand/model/ interesting to hear what you recommend...
FollowupID: 6339

Follow Up By: Oziexplorer - Friday, Jan 17, 2003 at 09:07

Friday, Jan 17, 2003 at 09:07
Robert I have two BP Solar SX75 multicrystaline panels with a Maitland Enterprises regulator, which can be purchased from Jaycar and is part number: MP3126 This is an Australian made switch mode regulator that is excellent.
I run the power from these into an Apollo 882 90aH battery
These are made by Global Yuasa in Korea and are proving to be a good battery, and better than some others that are a fair bit more expensive.
I have the solar panels mounted on top of my 4WD which has an enclosed body on the back. The solar panels are easily removed so they can be placed on the ground in the sun when you park in the shade.
I have a 6 metre 6mm twin sheathed oxygen free copper cable connecting the solar panels to the vehicle.
The two panels give us more than adequate power all year round. In winter you have to turn the panels into the sun twice a day to ensure you get enough sun, especially if the weather is poor a few days in a row. To date we have never run out of power, even when we had 2 x 60w panels. I like solar panels as they give no trouble, silent, a one off cost and then free. The majority of quality solar panels have a 25 year warranty. I look at solar panels like getting gold out the ground. It is like getting money for free. When you look at the cost of a small generator and then still having to put fuel in and service it etc. solar panels are a similar price, and last for so long without maintenance and ongoing costs and are environmentally great.
FollowupID: 6350

Follow Up By: Member - Robert - Friday, Jan 17, 2003 at 22:21

Friday, Jan 17, 2003 at 22:21
Great. Thanks for that Ozi.
Any reason why you went for the BP panels? How would you rate them against the Unisolar?
...and you only run one battery.
FollowupID: 6394

Follow Up By: Oziexplorer - Friday, Jan 17, 2003 at 22:39

Friday, Jan 17, 2003 at 22:39
Robert I do not like amphourous panels for all the right reasons. One big reason, is the substantial extra size they are compared to multicrystiline panels. Performance all year round on amphourous is not the best and you consequently need an extra panel in winter.
FollowupID: 6395

Reply By: rodeoowner - Wednesday, Jan 15, 2003 at 22:22

Wednesday, Jan 15, 2003 at 22:22
Nobby, I have an old Overlander magazine with a fridge comparison in it. One of the fridges is the 60L Trailblaza. The test results were;

23 amps @ 24 deg C - 4.5deg C inside
30 amps @ 35deg C - 4.3 deg C inside

Bear in mind that while the tests were carried out over 24 hours, this did not include any openeing or closing of the fridge, for which which draw many more amps. The comparison included fridges of many different sizes, but was very interesting.

For interests sake (figures for 12 hours at 35 deg C, 12 hours @ 24 degC)

Explorer 56L: 37.09 Amps/day Engel 29 L: 20.81 amps/day
Indel B 52L: 27.59
Swagman 60L: 40.25
Kidmans 45L: 26.5 (fridge is based on Evacool box NLA??)
Trailblaza 60L: 26.33
Autofridge 39L : 14.81

Please note also that all fridges were set at around 4 degC and were cooled to this temperature when the stop clock was started.

AnswerID: 11355

Follow Up By: Oziexplorer - Thursday, Jan 16, 2003 at 01:08

Thursday, Jan 16, 2003 at 01:08
Rodeoowner that must be one awfully old antique magazine. How old is it?
Half those brands are no longer available, and none of the others would have the current model BD35 Danfoss compressors in them. For the brands that are still around, I think I can safely say everybody has since brought out new models.
FollowupID: 6280

Follow Up By: Topcat - Friday, Jan 17, 2003 at 23:21

Friday, Jan 17, 2003 at 23:21
This one is to Oziexplorer & I may be a bit biased toward the Trailblaza fridge. I bought mine over 15 years ago & considering that it has been over some of the roughest country in Australia it has never broken down.I have never had a problem with energy consumption provided you give it good ventillation & don't have it sitting in direct sunlight. The only reason I switched from Engel (I had a 40litre for 5 yrs previously) was that it needed all that anti vibration setup, otherwise it would shake itself to bits. Mind you they have improved over the years. But getting back to the Trailblazer. I normally run mine in the full freeze condition having precooked & frozen my food prior to going on a trip. I find it runs more efficient this way then running in a fridge/freeze setup. Prices these days on portable fridges have risen dramatically considering that I paid $880 for mine back in 1987. The Engels were the only other real competitior around at that time that I knew of. So all I can say is I reckon I've got my money's worth!!!
FollowupID: 6400

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