evakool fridge help

Hi all,
I have a evakool 60 litre fridge with the external motor that is having trouble running on 12 volts, i have done some test today, I am now baffled with the results any help or suggestions would be much appreciated.

Test: run the fridge on the car spare agm 90 a/h battery, 6mm wire & Anderson plug & the fridge cut out at 12 volts so i connected the 240 v power supply to the fridge and it run fine. so i tried another battery that had 11.7 volts and same result the compressor would kick in for only about 5 seconds then drop out. so i chased the wires right back to the circuit board on the fridge testing to see if there was any volt drop it measured 12 volt at battery and 11.8 at circuit board so there should be plenty of power to run the fridge.

Any ideas what it may be.
Thanks Mark
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Reply By: KenInPerth - Friday, May 17, 2013 at 19:32

Friday, May 17, 2013 at 19:32
Mark

When you say you connected the 240V supply, if it is like mine the supplied 240V supply is a 240V AC to 24Volt DC power supply - is that the case with yours ?? That could account for why it runs fine on the "240V" supply (which is actualy 24Volt DC into the the fridge).

Also, are the voltage measurements you are taking under load or with nothing connected to the battery ??

Some possibilities are:

1. the low voltage cut out of the fridge has strayed from the 10.9V or whatever it is to something a lot higher.

2. your readings are inaccurate if taken with no load - they need to be measured with a similar load to the fridge (say with one or two 12V 21W car globes) at the end of the run (where the fridge would be connected).

3. your meter is faulty / inaccurate by a large amount.

AnswerID: 511262

Follow Up By: mark4 - Friday, May 17, 2013 at 20:36

Friday, May 17, 2013 at 20:36
Hi thanks for the reply
The 240 volt supply does sound to be the same as yours, The fault light is coming on the fridge indicating that it has low volts, as for the test i did do it with no load i will try in the morning and c what results i get. so if i checked the battery at 12 volts (no load) does this mean that it will not be an accurate reading to what the fridge requires under load.
also when i start the car the fridge runs fine it has a bcdc charger.


Thanks Mark
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FollowupID: 789446

Follow Up By: KenInPerth - Friday, May 17, 2013 at 23:03

Friday, May 17, 2013 at 23:03
Mark

Yes - it is essential to measure Voltages under load conditions - depending on the condition of the battery and any other losses in the circuit you can get a very different readings under load.

Given you have also said it works OK if you start the car that would indicate it is just not running due to either available voltage when on battery only, or as Batt's said (from experience) the cut out is set too high.

It might be worth checking the voltages with the car started at the output of the charger as compared to that at the fridge to see if you have any significant loss in the cabling.

Lastly if possible you could be measuring the voltage at the fridge and get someone to turn the engine off and you might be able to roughly determine the cut out voltage of the fridge (and will also see if the voltage drops off rapidly due to the condition of the battery).
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FollowupID: 789468

Reply By: Batt's - Friday, May 17, 2013 at 21:04

Friday, May 17, 2013 at 21:04
I had that problem yrs ago to it to evakool they lowerd the voltage cut out it was set to high from the factory
AnswerID: 511271

Reply By: Evakool - Saturday, May 18, 2013 at 12:00

Saturday, May 18, 2013 at 12:00
I have attached a couple of information sheets that should help with your issue.

Thanks


AnswerID: 511301

Follow Up By: KenInPerth - Saturday, May 18, 2013 at 12:42

Saturday, May 18, 2013 at 12:42
I have often wondered why you set the cut off voltage so low

Is it because

1. the battery can (or should be) capable of that sort of discharge / recharge without short term consequence to the battery.

2. it is considered most important to keep the fridge running as long as possible ...


Ken
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FollowupID: 789497

Follow Up By: Evakool - Saturday, May 18, 2013 at 14:03

Saturday, May 18, 2013 at 14:03
Hi Ken,

To answer basically, just because the Voltage cut-out inside the fridge is set at 9.6 Volts does not mean the battery will be discharged to this level, as even on a well setup system the battery will normally only run down to around 10.5 Volts but on a lot of systems the fridge will stop well before that Voltage is reached (12.0 Volts or higher as below).
Of the two options you have given I would suggest option 2 is important for a lot of people, that don't mind how or why, they just want to plug the fridge in and it run for as long as possible.


To answer in more detail;

The lowest Voltage cut-out a Danfoss 101N0210 or 101N0220 electronic box can be set to is 9.6 Volts on the 12 Volt side. This is the standard electronic box that is used with the Danfoss BD35 and BD50 Compressors. The default cut-out is 10.4 Volts.
Evakool originally used the default of 10.4 Volts but changed the cut-out to 9.6 Volts around 2005.

There is around 0.2 Volt drop through the cabling inside an Evakool fridge (from the electronic box to the 2 pin power outlet) and around 0.2 Volt drop through the standard cigarette cable. This Voltage drop is based on a number of factors including the cabling being in factory condition and assuming an average Amperage load (the Amperage draw based on many different factors).
So if the Voltage cut-out was 10.4 Volts at the electronic box and there was a 0.4 Voltage drop to the end of the cigarette lead then fridge will run until the Voltage drops to 10.8 Volts at the end of the cigarette lead.
Assuming another 0.5 Voltage drop through the vehicles cabling then the fridge will stop when the battery has dropped to 11.3 Volts.
Depending on a few factors this could indicate a lead acid battery that has around 20 - 30% capacity left. It could be argued that this is still too low a state of charge to run a battery down to but as long as a high quality battery is used and the battery is recharged soon after reaching this point it should still have a long life.

Unfortunately we at Evakool, as have many other companies / people, have found out that most vehicles in standard form (and some that have been modified) are not close to only having only 0.5 Voltage drop when running a fridge.

This means if the Voltage cut-out was set to 10.4 Volts, assuming a cut-out point around 10.8 Volts at the end of the cigarette lead and a 2 Volt drop through the vehicle’s wiring then the fridge would stop when the battery was at 12.8 Volts. This would mean the fridge would stop working soon after the vehicle's engine was turned off.
If on the same system the Voltage cut-out inside the fridge was changed from 10.4 to 9.6 Volts then the fridge would continue to run until the battery was around 12.0 Volts. This would give a much longer run time.

So, as shown above, depending on different vehicles / setups the same Voltage cut-out can mean the battery discharges to very different points.

So setting the Voltage cut-out has to be a careful consideration but in most circumstances it is very important not to set the cut-out too high.


Thanks.
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FollowupID: 789506

Follow Up By: mark4 - Saturday, May 18, 2013 at 18:34

Saturday, May 18, 2013 at 18:34
Thanks all

Your input has been much appreciated & after running a few test under load showed me that the fridge was dropping below the volt range required to run the fridge. i did have the battery load tested a couple of weeks ago and he said it was fine but to do a true reading he would need the battery all day. I have decided to buy a new battery and see how it goes as i have had an excellent run out of my current battery.

Mark

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FollowupID: 789534

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