Firstly, (and I fear this will upset a few excellent tradespeople), I have come to the belief that the gulf between car / truck electrics and motorhome electrics is so great that it is a waste of time, energy and cash to approach most auto-electricians for specialised motorhome electrics. Auto-electricians have a great deal of expertise in their trade - but it's a substantially different trade, particularly where solar systems are involved.

Instead consult an accredited 'Remote Area Power Systems' installer. System required for motorhomes are very similar to those required for small houses - and these people know such systems inside out (indeed many include suggested motorhome configurations in their literature).

They are to be found in all states of Australia , and many are listed in the extremely interesting quarterly publication ReNew - available from all major newsagents. (Tel: 03 93889311). Alternatively ring the Solar Energy Industries Association of Australia Inc, (02 99883074) and ask them to send you a list of accredited members.

Solar Panels
Recent sales promotions claim/ suggest that Uni-Solar panels (marketed in Australian by Canon) produce higher output than competitive units of similar nominal ratings. A number of members have asked me if this true.

Most solar panels have similar characteristics: in real life they produce a maximum of 65%­70% of that suggested in the large print when used with 12 or 24 volt systems. Uni-Solar panels use a different technology. The panels initially produce 10% - 15% more than competitive panels of the same nominal rating, but revert to substantially similar outputs as their competitors within a month or two of use. Both Canon and Uni-Solar spell this out very clearly indeed in their technical literature.

Where Uni-Solar panels do score, at least for mobile use, is that even a hand-sized shadow causes most other panels to effectively shut down. Uni-Solar panels however only lose output more or less in proportion to the area shaded. The panels are also less prone to lose output as cell temperatures rise, but this is only a serious issue with so-called self­ regulating panels, or with interactive grid systems (not relevant for mobiles!).

Optimal angling of solar panels in mobile installations is only worth while in the more southern parts of Australia . and, in all areas, maximum output in cloudy or overcast conditions will generally be obtained with the panels mounted flat on the roof. Adding 20% more solar panel will adequately compensate for loss through non-optimal alignment.

Generators
There's all-but universal misunderstanding about portable generators and battery charging.

Almost all portable generators are designed to power 230/240 volt AC equipment for short periods. Some also have a 12 DC volt output intended for the direct connection of 12 volt appliances. The voltage output is kept below 13 volts to avoid damaging 12 volt appliances. Thirteen or so volts is far too low for battery charging. The generator manufacturer may recommend that the output be floated across a 12 volt battery, but that battery serves only to stabilise the output, it will not be meaningfully charged.

A vaguely satisfactory solution is to use the 230/240 volt AC output to power a conventional mains battery charger. This will work well enough for 5 amp chargers, however the (electrically inductive) nature of all but a handful of very costly (switch mode) chargers is such that they place a far greater load on a generator than arithmetic might suggest. One reputable supplier states that 5 KVA generator sets are rarely capable of driving even 1.5 KVA chargers! The most you can realistically expect from a 350 watt generator is about 5 amps - and that's an incredibly costly way to charge a battery.

Many portable generators have a designed life of only 1000 or so hours, and even this is unlikely to be achieved if regular oil changes (sometimes at scheduled 20 hour intervals!) are neglected. Reasonable or otherwise, the failure to do this was the main cause of the woes some members reported with one particular generator a year or three back.

Generators suitable for battery charging are available in the USA , but even there, are rare and costly. A cheap solution is to build your own using a car or truck alternator and suitable engine (a 1.5-2.0 HP engine will comfortably drive a car-sized alternator.

Interior Lighting
The choice is logically dictated by the following data. In order of efficiency:

Hybrid fluorescent (65 lumens/watt)

Fluorescent (42 lumens / watt)

Quartz Halogen (12 -171umens/watt)

(12/24 V) Incandescent (9 lumens / watt)

(Loosely speaking, a 'lumen' is a measure of light output, the more lumens per watt of electricity, the more efficient the light source.)

If energy saving is an issue, the choice is obvious: a hybrid fluorescent uses only one / seventh the energy of the car-type incandescent globe and about a quarter of that of a 20 watt quartz halogen. (An 18 watt hybrid produces about the same amount of light as a 100 watt domestic globe).

Don't economise on these devices. Good hybrid fluorescent tubes, such as Philips, cost $40 - $50. The $15 - $17.50 supermarket specials will prove to have a very short life indeed!

Wiring
Voltage drop is a much bigger problem at 12 volts than at 240 volts. Twenty times bigger in fact. Two volts drop at 240 volts represents less than one per cent of the output, the same drop at 12 volts is a loss of close to 20%. Thus a cable capable of carrying 10 amps at 12 volts needs to be a great deal larger in cross-section than a 10 amp cable intended for 240 volts. This is, understandably perhaps, rarely understood by hardware stores. Buy your cable from an auto-electrician or boat supply store.

To avoid long-term corrosion, particularly if you are planning to spend much time dose to the coast, it's best to use 'tinned' copper cable. It costs a bit IT:.O~ than normal copper cable and can be hard to find - if in trouble consult the sources quoted at the end of this feature. I've put 'tinned' in inverted commas because whilst universally called such it is actually a nickel-alloy electroplate.

As a rough guide, for cable lengths up to 10 metres, use cross-section areas of 1.8 mm for loads up to 5 amps, 2.9 mm up to 10 amps, 4.6 mm up to 20 amps. In all instances the loss will be an acceptable 5% or so at the maximum distance quoted. You can come down one cable size if the cable route is shorter than 5 metres.

Plugs/Sockets
Do not even think of using cigarette lighter plugs and sockets for anything but the lightest of loads (preferably not at all) . I have personally experienced two vehicle fires directly caused by arcing within these literally infernal devices.

Whilst not the most aesthetic, but by far the best, 12 volt connectors are those made by Bulgin (obtainable from Electric Boat Parts). If you elect to use these.- choose the three-pin 10 amp version - which for marketing reasons are a lot cheaper than the two-pin 10 amp version.

Alternatively, country electrical wholesalers often stock 12 yolt sockets generally similar in appearance to domestic 240 volt devices (but with one vertical and one horizontal. pin). If you can't locate them contact Rainbow Power Company in Nimbin - who are a gold mine of information and a source of most bits you'll need. There is no standard on wiring these sockets, but most electricians use the horizontal pin as positive - the essential thing is to have them all the same as correct polarity is essential to many DC appliances.

Jumper Leads
As many a big-rig owner has found to his or her cost, few commercial jumper leads are capable of handling the plus 500 amps required for turning over a large cold diesel. Make up your own, or have an auto-electrician make them for you using 6: mm OOBS) truck-­gauge battery cable.

Phantom Loads
Several readers have found that their systems continue to draw power when all connected equipment is turned off - in one instance the 'leakage' was over 2 amps.

A lot of today's electrical equipment continues to draw power whilst switched off at the appliance. This is particularly true of 240 volt plug-in adaptors that typically power mobile phones, lap top computers etc. In many instances these devices draw more power than the load they drive. TVs, VCRs, and many recent washing machines, microwave ovens etc incorporate filters etc that draw energy continuously. Sometimes energy is required to run an internal clock, but where such need is vital there will be an internal battery. To be certain no power is being drawn, turn off appliances at the wall switch.

Rust Protection
An ongoing problem especially with older vehicles, protecting against rust has recently become easier following the adaptation of the cathodic protection technology long used in the pipe-line and other industries to cars and trucks. This should not to be confused with the sacrificial zinc technique used on boats.

The technology will not totally prevent rusting, but effectively slows it down. The more responsible elements in the industry claim it reduces rusting 'by four to five times'.

In conjunction with Australian 4WD magazine and Endrust, I have been running a long ­term test of the locally-made Endrust Electronic Rust Protection product. About six months into the test, protected test strips on our OKA have far less rusting than adjacent but unprotected (i.e. electrically isolated) test strips which are now heavily rust-pitted. Further, the rust coating on the protected strips is of an apparently different nature. It readily wipes off with a cloth.

A bonus, experienced by us and also reported by many users, is that the paintwork retains a 'bloom'. The Endrust devices really need specialist fitting by selective Endrust agents. If unable to locate an agent, telephone Alan Anderson (Managing Director) at Endrust in Sydney (02) 9790 7155).

Communications
CB radio is useful if travelling in convoy, but unless motorhomers agree on a common­ usage channel, has little use otherwise. It should not be relied upon for emergency communications as maximum range is more or less limited to line of sight.

HF radio is still used by those venturing into the outback. Recent versions incorporate direct connection to the Telstra public telephone network. There is also a useful user ­network for outback travellers. But HF radio is nevertheless a clumsy and now use ­overcrowded technology that has been overtaken by satellite telephony.

Whilst still costly to buy and use, a satellite telephone can provide Australia-wide coverage. As a generalisation, the Telstra system has better coverage for coastal Australia , the Opus system has better coverage within Australia - particularly if used with an active dome antenna. We have the latter set-up and have found it reliable, effective and trouble ­free despite being battered over seriously rough outback going - including the Simpson, tip of Cape York etc.

Telstra's new digital CDMA system is intended as a high-technology replacement for the previous analogue network only. Telstra states that CDMA may have marginally better coverage in some areas than its analogue predecessor but the areas to be covered will be substantially as before, excepting that it will also include all areas covered by the existing GSM digital MobileNet service.

Low-orbit satellite systems should begin to come on-line within two to three years. The forthcoming technology will provide lowish-cost access from almost anywhere, but CDMA or similar will still be required for indoor reception. Because of this, future handsets are likely to be dual-mode, automatically selecting the available system.

E-mail
E-mail can be successfully implemented via mobile telephone (where there is Telstra MobileNet coverage), or via either Telstra or Optus satellite telephone.

The data rate is very restricted, so e-mail transmission needs to be confined to text messages only - or you'll end up with huge phone bills. Implementation can be a bit tricky, as can finding a supplier who knows how to do it. It's essential to use an ISP (Internet Service Provider) whose servers can cope with the very slow transmission involved. Ozemail is said to work fine. (I use rivernet - but mostly out of vanity ­ collyn@rivernet.com.au ). A good hint is to get the system up and running over a normal telephone line, with your modem data rate restricted to a maximum of 9600 bits/s before attempting to cut over to mobile.

Keeping the Inside Clean
Here's a really worthwhile tip, picked up from a police sergeant we met in Gunlom (Kakadu) a few years ago.

Lay a suitable length of shade cloth (obtainable for a few dollars a metre from any hardware store) along the full length of the vehicle, peg it down if necessary. Sand, dirt, dust etc will fall through the holes in the cloth leaving a far cleaner surface than you'll ever obtain from more costly matting.

Mail
For those more or less permanently on the road, Landbase Australia . (Locked Bag 25, Gosford 2250) provides an economic and extremely reliable mail forwarding service. Mail is forwarded in sequentially-numbered bags (usually by parcel post.) following telephoned destination advice.

The only minor drawback is incurring forwarding postage for the unsolicited junk mail that inexorably follows if one orders or subscribes to anything by mail-order. If anyone knows an effective way to turn-off these pests (Innovations has so far been totally impossible for us to shake loose despite constantly returned material letters, and latterly abuse) please, please let us know.

Recommended Suppliers:

David Watkins, Electric Boat Parts, Roseville , NSW . Tel: 02 9417 8455. Top (marine) quality electrical fittings, cable, lugs, smart regulators etc. Sorry if this sounds overly promotive, but if you want the best product available in each field, this company will probably have it. They have an excellent mail-order service. Ask David for his catalogue.

Quirks Victory Light, Rose Bay NSW. Tel: 02 9371 6600. Very .wide selection of low voltage appliances - also builders of the excellent Autofridge. A note for any chauvinist male readers - Quirk's is owned and run by women. Virtually all them know more about electrics than you'd believe possible - so don't be patronising.

Rainbow Power Company (Nimbin) NSW. Tel: (066) 89 1430. Suppliers of solar everything. The company's 'Energy from Nature' handbook is a somewhat messy but extraordinarily useful good-value reference to alternative power generally.

Whitworth Marine (various outlets in NSW and Qld). Has an extensive range of fittings, but also of a wide range of quality particularly in their electrical bits and pieces. Worth looking around but you need to be selective.

The quarterly publication ReNew - available from all major newsagents Tel: Q3 9388 9311) carries advertising from a very wide range of suppliers of solar and low voltage equipment. Particularly valuable for owners of medium/big rigs - where the needs are very similar to small remote area houses (such as the one Maarit and I are about to build 20 km north of Broome).

Much of the material in this, and my previous Motorhome Electrics series is a very much condensed version of material from my nearing-completion book on all aspects of campervan and motorhome usage.

I hope that even if this three-part series has not given you all (or any of) the answers, it has at least helped you formulate some of the right questions!