Words and Images by: Collyn Rivers N8054

The initial part of this article (last month) related to the problems many RV owners experience when travelling in Australia’s far north: particularly with electric compressor fridges.

It emphasised that, contrary to common belief, not only is less solar energy available (than in a southern summer), but that the energy needed to drive a fridge increases by 10% for every 5.C above an ambient temperature of 25.C. During a northern June to August the energy increase is about 5%, but for most other months it is 10-15%.

Particularly overlooked too is that northern coastal areas remain warm all night as well as all day.

The 24-hour fridge energy draw thus typically increases by 20-30%; and a probable 40% plus for those partial to cold tinnies, and chilled wine.

Not only is less solar energy available, but energy draw is higher. Some fridges may cope, but gobble energy to do so. Many however just gobble energy.

Fridge Installation

With a likely total energy discrepancy of some 50%, many RV travellers have serious fridge and battery issues.

In many (probably most) RVs, the fridge is very far from competently installed. Doing it properly is not that costly, but usually time consuming. It is likely to need removing as cabinet work is often required to ensure adequate ventilation - often at its rear.

The typically used 12/24 volt dc compressor fridge, e.g. Engel, Waeco etc, will also almost certainly need rewiring with far heavier cable. Most can have their performance improved considerably, some dramatically, by this alone.

A corollary of the above is interminable camp-fire and forum discussions about perceived fridge merits and failings that are, in reality, almost totally about the often lacking quality of their specific installations.

Details of how to do this are in my articles in the CMCA website archives. Constantly updated versions are in all of my RV and solar relatedbooks – and also at:  http://www.caravanandmotorhomebooks.com/ articles/installing-rv-fridges.html

Despite the ongoing 40.C whilst camping in Kakadu National Park, we still baked fresh bread most days - it’s in a Bedourie oven under that spade; that also warns not to walk there barefoot! The 71 litre eutectic style fridge (visible through the entry door) coped with ease - drawing a mere 40 amp hour a day from two (nominal) 80 watt solar modules above the driving cab. The fly mesh screened rear window provided ample air movement at night. Pic: Author 1998 (Pix copyright Caravan & Motorhome Books).

The Golden Rule

Unless your solar set-up, in typical daily southern use, has the proven capacity to fully float the batteries by midday on most days, it has no chance of working adequately up north at any time of year.

Increasing battery capacity alone inevitably worsens the situation. It is like spending more money than you earn - and then hoping that obtaining a second credit card will fix the problem.

Most rigs have grossly too little solar even for their existing battery capacity, let alone more. With solar, nothing really succeeds like excess! With batteries, use the minimum feasible capacity (they will charge far quicker, and with less sun).

Converter Systems

No RV fitted with a basic ‘converter’ 12 volt electrical system is likely to cope for more than 12 hours up north, even in June-August, unless  that system is fed by a 230 volt ac supply. (The Wanderer Tech Notes March 2013 explains why.)

A forthcoming Tech Notes will show how to at least partially overcome what is now known to be surprisingly widespread issues with these units - if they are used for other than their intended purpose - and that does not include camping for extended periods away from 230 volts mains power.

None but ‘T-rated’ three-way fridges cope above ambient of 36.C whilst up north. If correctly installed ‘T-rated’ units will, continue to meet specifications in ambients up to 43.C.

Generator Back Up

I dislike advising this, but if planning to spend only a month or two up north, a practical solution is to rent or buy a 1.0 kW Honda or Yamaha inverter generator (or 2.0 kW if air conditioning is required).

To avoid running it for long periods, if feasible use its 230 volts ac output to power a high current multi-phase battery charger.

It is safe to charge a deep cycle battery at up to 20% of its amp hour rating, and an AGM at 30%, e.g. a 100 Ah deep cycle battery may thus be safely charged at up to 20 amps, a 100 Ah AGM at up to 30 amps.

Collyn Rivers

Category: Technology
Written: Tue 01 Oct 2013
Printed: October, 2013
Published By: