Cir­cuit work

Motorhome & Caravan Trader - - Tech Talk -

Car­a­van electrics are con­stantly evolv­ing, with in­no­va­tions such as lithium bat­ter­ies chang­ing the game, but there is still plenty to keep you busy with the more hum­ble elec­tron­ics you may have in your cur­rent van.

Car­a­van elec­tri­cal sys­tems used to be dead-sim­ple, but the ever-in­creas­ing num­ber of con­ve­nience items cam­pers want and the var­i­ous ways of pow­er­ing them have made mod­ern car­a­vans a bit more com­plex.

Re­mem­ber, only a li­censed elec­tri­cian is legally per­mit­ted to work on high-volt­age (240V) electrics. For any work beyond re­plac­ing a 240V globe or fuse, you must call in a li­censed elec­tri­cian.


How­ever, it doesn’t hurt to see that your van is up to the (elec­tri­cal) load you are putting on it. If you have the cor­rect gauge wiring in your van with ap­pro­pri­ate cir­cuit break­ers – and al­most cer­tainly all do – there’s no rea­son why you need to worry about run­ning high cur­rent draw items, such as air-con­di­tion­ing, if you are al­ways us­ing 240V mains power to do so – pro­vid­ing that you’re not try­ing to use too much elec­tri­cal equip­ment at the same time.

When staying at pow­ered sites, there is lit­tle to worry about ex­cept for us­ing an in­dus­trial-rated 15A lead to plug into the mains socket and to make sure you have bought a lead of the cor­rect length – you can’t pig­gy­back leads.

While the whole con­cept of on­board electrics is chang­ing quickly – with the in­tro­duc­tion of lithium bat­tery tech­nol­ogy, for ex­am­ple – most mod­ern car­a­van elec­tri­cal sys­tems run a hy­brid of 12V, pow­ered by lead-acid deep-cy­cle bat­ter­ies, and 240V pow­ered by mains or gen­er­a­tor. A key heavy cur­rent­draw item is the re­verse-cy­cle air-con­di­tioner, which can only run on 240V, while other electrics, such

as LED light­ing, run on 12V power from ei­ther an in­verter con­vert­ing the 240V mains power to 12V or from an on­board bat­tery, which it­self is charged through a charger hooked up to 240V mains power. The house bat­tery can also be charged by the tow ve­hi­cle’s al­ter­na­tor through the trailer plug.


The ‘right’ power sup­ply is de­pen­dent on many things, par­tic­u­larly how long you plan to stay of­f­grid. If all you do is step into the van to turn on a light and make a cup of tea on the gas ring dur­ing your trans­port stages, you won’t have too much of a prob­lem.

As­sum­ing you haven’t plugged into a faulty mains socket at the car­a­van park (that can hap­pen, so don’t as­sume that the fault lies with your van), the ca­pac­ity of the charg­ing sys­tem and bat­tery stor­age only be­comes a po­ten­tial is­sue when free camp­ing. If you haven’t cal­cu­lated your power re­quire­ments, you could have more can­dle-lit din­ners than you ex­pected.

If you’re run­ning a fridge off your tow ve­hi­cle, don’t for­get to switch over the fridge to gas or 240V when parked up overnight. You could be sur­prised by a flat bat­tery in your ve­hi­cle when you hitch up to head off in the morn­ing; how­ever, a bat­tery iso­la­tor fit­ted to your ve­hi­cle will fix this prob­lem.

You can work out with your car­a­van elec­tri­cian what bat­tery will work best for your re­quire­ments but, gen­er­ally speak­ing, a 100Ah deep-cy­cle bat­tery with so­lar panel or por­ta­ble gen­er­a­tor back-up will do the trick. The key is to not get too am­bi­tious with elec­tri­cal equip­ment, and to have enough so­lar pan­els or gen­er­a­tor time to ad­e­quately charge the bat­tery.

It is pos­si­ble to put too much load on the 10A car­a­van sys­tem. Try­ing to use an elec­tric ket­tle and four-burner toaster at the same time, for ex­am­ple, will trip the cir­cuit breaker. If you per­sist with us­ing too-high cur­rent elec­tri­cal items at the same time and keep trip­ping the cir­cuit breaker, it’ll weaken it and cause even big­ger prob­lems that could even­tu­ally lead to an elec­tri­cal fire. Plug-in hot wa­ter sys­tems are a prime ex­am­ple of a piece of elec­tri­cal equip­ment that should be wired sep­a­rately with its own ded­i­cated cir­cuit so as not to over­load the car­a­van’s 10A sup­ply.

If your cir­cuit breaker keeps trip­ping, un­plug all 240V equip­ment in the van and try the switch. If the cir­cuit breaker trips, it could be faulty it­self, or there are other, more sig­nif­i­cant, prob­lems. If it doesn’t trip, then you can plug-in the 240V ap­pli­ances oneby-one un­til you find the cul­prit over­load­ing the cir­cuit.


An op­tion for quick power is to use a por­ta­ble gen­er­a­tor, and some quiet op­tions are avail­able (such as the Honda units). The neg­a­tives are that they aren’t cheap, at about $1500 for a good one, plus gen­er­a­tors are heavy and most na­tional parks camp­grounds ban their use. You also have to carry a sup­ply of fuel to run it. Both the gen­er­a­tor and its fuel sup­ply add a good chunk of weight to your pay­load.

Bat­ter­ies are a bit like tyres in that, once they get old, they don’t work as well. You’re un­likely to get a spec­tac­u­lar blowout as you might with an old tyre, but the bat­tery will not hold as much charge and thus can be­come frus­trat­ingly in­ef­fi­cient.


If the elec­tri­cal sys­tem is not work­ing, you can check the sim­ple things: a charge me­ter is of­ten sup­plied in vans, so check that at least 12-13V is avail­able. If you don’t have a me­ter, get a mul­ti­me­ter and check across the ter­mi­nals to see the volt­age dif­fer­ence. Once you get down to around 11V, the sys­tem is un­likely to pro­vide enough power. Ide­ally, you should have 13-14V on tap in a fully-charged, healthy bat­tery.

Fuses or cir­cuit break­ers can fail or trip so check th­ese (al­ways carry known, good, spare fuses) and check that mois­ture has not cor­roded any fuse connections. If lights do not work, the ob­vi­ous thing with older vans is to check for a blown globe, but also check the connections as they can cor­rode.

If the cir­cuit breaker keeps trip­ping (and it’s un­re­lated to high cur­rent­draw equip­ment use), or globes keep fail­ing, there is a short-cir­cuit or cur­rent surge that should be in­ves­ti­gated by an elec­tri­cian.

When mak­ing ad­di­tions to your van, such as screw­ing in a new bracket or shelf into an internal wall, don’t for­get the wall is very thin and you could dam­age elec­tri­cal wiring run­ning on the other side of the pan­elling.

Mois­ture and cor­ro­sion in elec­tri­cal sys­tems can pose sig­nif­i­cant prob­lems and they are very hard to track down. If you have an elec­tri­cal fault that does not have an ob­vi­ous so­lu­tion, such as a failed globe or fuse, then it could be a loose or cor­roded earth point. Check all earth connections for cor­ro­sion by dis­con­nect­ing, clean­ing and re­con­nect­ing them.

The seven-pin plug con­nec­tor can cause prob­lems if you do not hold the con­nec­tors to pull apart (that is, don’t pull by the wiring or wiring sleeve it­self) and if there ap­pears to be a bad con­nec­tion, check the pins on the plug have not com­pletely closed up.

When stor­ing the car­a­van for long lay-ups of a month or more, take out the bat­tery and oc­ca­sion­ally check its charge with a mul­ti­me­ter and trickle charge as nec­es­sary (if, say, it drops to less than 12V). Cer­tainly do not let it de­plete much lower than this as it will per­ma­nently dam­age the bat­tery (par­tic­u­larly if it’s a start­ing bat­tery, but a deep-cy­cle is far bet­ter for car­a­van ac­ces­sory use any­way).

Clock­wise from top left: The in­creas­ing num­ber of con­ve­nience items in RVS means pow­er­ing them has be­come more com­plex; bat­ter­ies are some­times car­ried un­der the chas­sis for easy ac­cess; air-con­di­tion­ers are a very high-draw ap­pli­ance; mod­ern elec­tri­cal s

From top: Take care when drilling into pan­els, you could be drilling into your van’s wiring; too many high-draw items may cause the safety switch to trip; a typ­i­cal on­board car­a­van bat­tery in­stal­la­tion.

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