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This is a fairly simple, and basic, introdiction to the motorhome electrical systems. I've tried not to pverlap with more detailed articles which will follow. As always, any suggestions for improvement would be very welcome.
Introduction to motorhome electrical systems
There are up to 3 electrical systems in your motorhome. These are:
1) Cab (engine) 12 Volts dc
2) Habitation area 12 Volts dc
3) Habitation area 230 / 240 Volts ac
1) Cab
When the vans or motorhome chassis are built, they have a single 12V battery installed which has a function similar to a car battery. It will start the engine, and is charged by the engine-powered alternator. Most motorhomes have a cigarette lighter-style socket for accessories in the cab area.
2) Habitation 12V dc
Most motorhomes have a 12V dc supply into the habitation (living) area of the motorhome, powered by one or more habitation batteries. This powers devices like a fresh water pump, reading lights, and any accessory sockets in the habitation area for a TV or radio.
3) Habitation 230 / 240V ac
All recent motorhomes are fitted with at least one mains ac outlet socket. This is powered from a hookup connection, usually in the side of the van, which can be plugged in when on a campsite. It will allow the use of standard domestic electrical appliances, such as an electric kettle, microwave, TV / DVD player, etc. It can also power a built-in fridge.
NB Mains electricity in the UK always used to be a nominal 240 volts dc. However, the EU is standardising electricity supplies across Europe at 230 volts ac. Mains voltage also fluctuates within certain tolerances, and can be anywhere within the range 216 volts - 253 volts ac.
Habitation batteries are normally lead-acid, and as such have a finite amount of power stored within them. The battery can be recharged by running the engine (and alternator), or using the on-board charger with a mains hookup from either a campsite mains outlet or a generator. The battery can also be recharged by solar panel (usually mounted on the roof of the motorhome) or by wind generator (low efficiency).
Although the habitation and engine battery will both be recharged by running the engine, the system does not normally work the other way around (i.e. the engine battery will not be charged from a hookup). For this, you would need a Battery Master or similar device, although some newer motorhomes have this facility built-in.
Last edited by geraldandannie on Fri Apr 03, 2009 6:27 pm; edited 1 time in total
as this is for beginners and there is also something available called a 'Battery Master Switch' which does something quite different but in fact could be used to join two batteries might this be clarified a little further
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With Swift vans if you switch to cab battery on the control panel the cab battery charges so you can charge either but not both from an EHU.
I suspect that the same will be true of many others (though not I think explorer group vans)
With Swift vans if you switch to cab battery on the control panel the cab battery charges so you can charge either but not both from an EHU.
I suspect that the same will be true of many others (though not I think explorer group vans)
can anyone confirm if this works with the lunar roadstar?
I know this is pedantic, but can we stop referring to 240V mains supply and state 230V instead, since this is the UK and European standard. I think it is potentially confusing to use the out-dated metric.
I know this is pedantic, but can we stop referring to 240V mains supply and state 230V instead, since this is the UK and European standard. I think it is potentially confusing to use the out-dated metric.
Philip
the latest spec is
From 1 January 2004 the mains supply should be 230V (-6%, +10%), 50 Hz (±1%). ie a range of 216.2 - 253V
I know this is pedantic, but can we stop referring to 240V mains supply and state 230V instead, since this is the UK and European standard. I think it is potentially confusing to use the out-dated metric.
Philip
the latest spec is
From 1 January 2004 the mains supply should be 230V (-6%, +10%), 50 Hz (±1%). ie a range of 216.2 - 253V
From 1 January 2004 the mains supply should be 230V (-6%, +10%), 50 Hz (±1%). ie a range of 216.2 - 253V
so yes you are being very pedantic.[/quote]
OK, but I think you are missing the point slightly. There has always been a tolerance range around the stated standard. However, the term 240V as a 'standard' is no longer applicable. (As you have pointed out, the relevant Statutory Instrument now states 230V.)
I guess a lot of people, with little or no electrical knowledge, are unaware of the issue of tolerances, and if they read 240V in one context, and then see 230V stated elsewhere (for example on the output of a generator) they might think the two systems were not fully compatible.
Surely it is better to make all references consistent by using 230V.
Fair point, Philip, but I wonder just how many motorhome buyers would be aware of this? The fact that I wrote 240, although I'm aware that it's 230, shows that I'm still in the habit of calling it 230.
Fair point, Philip, but I wonder just how many motorhome buyers would be aware of this? The fact that I wrote 240, although I'm aware that it's 230, shows that I'm still in the habit of calling it 230.
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Our thoughts are with you Chris and Graham. Fighting with Mavis and Ray 
