Quote Originally Posted by ChrisF View Post
Thanks for all the feedback.

I have had an absolute flood of PM's regarding this thread. Some I will deal with later, as I would have to take my time to prepare a proper reply.

Here is one of the PM's I received (name with held, afterall it was a private message). I am answering here as I believe the answer relates to more people -

1. Can you please send me the updated PDF document of your article. - the pdf is attached to the first post of this thread
2. I bought my Prado and think the setup is done the OLD way, without the dc2dc . I am quite ignorant so please help. I bought an NL Portable Power Pack and an Deltec 105Ah deep cycle battery during 2012, which is fitted in the Offroad trailer. Does this NL-system now do the same as the dc2dc CTEK ?? Or would you advise I add an dc2dc unit?
I keep this NL b0x with the battery connected to electricity via an CTEK Pro Battery charger MXS10 on a constant basis when not in use. In spite of this I found that the battery now only can run my fridge( only) for about 30hours versus 48 hours when new?? Am I doing something wrong??
We are doing a single vehicle trip through Kaokoland in August and do not want to be stranded with no fridge/ or battery problems.

Regarding the battery in the trailer - due to the long cable runs it is highly unlikely that the alternator can charge it. A dc2dc system is recommended. In fact, for those that dont have the skills for this, look at the trailer kits sold by HcDP ....

You PM also talks of a 2nd battery and NL kit for the Prado. Battery in the front of the Prado ? In this case the NL kit could work - bearing in mind it is just a solenoid with a timer function, ie NOT a dc2dc charger. IF the battery is in the back of the Prado, I would recommend a dc2dc charger.

The battery is now only 2 years old and only delivers for 30 hours compared to its original 48 hours .... Sadly for most of us a 2nd battery is an item that only WORKS 2 or 3 weeks per year. Batteries dont like standing idle.

I just dont know enough about batteries to comment on your battery question - lost my previous battery in a very similar manner.

If I may comment on battery power vs refrigerator runtime (I have been in refrigeration for 26 years and at one time worked for a company that built off-road refrigeration units)

Asking about how many hours of runtime a battery will provide is like asking how long is a piece of string. Modern day 220vAC / 12vDC compressors have come a long way as far as energy efficiency goes but it is still somewhat up to the owner of the fridge to get maximum runtime from the 12v power source, in this case to be the deep cycle battery. Rule of thumb would be for a Danfoss BD35 compressor (which I tend to use to provide calculations) to run continuously for 18 hours non-stop, would drain a fully charged 105ah deep cycle batt in this time span. Some people might get 2-3 hours less and some would get 2-3 hours more but this is basically what you are looking at.

So, in order for you to get more out of your power source would be manually to MANAGE your refrigerator runtime. If your engine is running and the batt is charging, you would have no problem in providing the correct and sufficient power to run the refrigerator. However, when your engine is switched off, the fun and games begin. So, good advice would be to set your thermostat (temp controller) to the coldest setting while the engine is providing the battery with charge and when you stop to overnight, set the temp to a higher setting like -2 to reduce runtime of the compressor. Some people even switch the fridge off completely at night or "stagger the runtime from the battery alone for a few hours and then switch it off. When you drive further again the next day, re-set the thermostat to the coldest setting to freeze up and replenish lost temp due to the reduced night runtime or even when it was switched off completely.

You need to get the most out of the battery and refrigeration as possible. Off course, this is not where it stops. Stainless Steel fridges are very nice looking but S/S attracts and relays heat very, very well. So a S/S fridge standing in the sun all day will require almost a third more runtime to maintain temp that a normal white fridge unless off course it is protected in some or other manner from direct sunlight. Thickness of insulation is also a very important factor to consider when buying an off-road fridge. the thicker the insulation, the better is maintains and hold temperature. Minimal opening and closing of the lid as well as making sure that the lid and the lid-seal seals properly is of utmost importance in temperature maintenance. Correct packing of the contents of the fridge in the order of how you will be taking items out can save quite a lot and reduces prolonged opening of the lid in order to "search" for the products you require for the day and by this losing valuable temperature inside the fridge. Pre-freezing of items needs not to be explained and if you are buying and stocking up on fresh supplies on your journey, learn to pack it at the bottom of the freezer as this will be the coldest place in the freezer.
Water or and form of liquid takes the absolute most refrigeration demand (Measured in BTU's) to cool down. If you are in a habit to add ambient temp water in large quantities into the freezer/fridge for drinking purposes, it will make the compressor work much harder to cool it down thus prolonging the compressor runtime by a whole lot more, which obviously will drain even more power from the power source.

There is so much more info on this and I'm sure most forumites know this and act accordingly, but I hope this might help a few out there to help manage the bushpower availability and fridge operations.