Leisure electrics 12v

Discussion in 'How To' started by matty, Dec 16, 2011.

  1. You've got a van and want to make the most of it as a camper. One of the main things you will want to do is think in advance about power and how to install electrics into your campervan.
    There are a number of issues relating to electrics in a camper. If you have any plans whatsoever to sit in your campervan for an evening with the lights on, music playing then I suggest you fit a second battery.

    Installing a Second / Leisure Battery in a Campervan

    If you don't install a second battery into your campervan to run key electrical items off, then either you will at some point run your van battery down to the point where you can't start the engine in the morning; or you will constantly be living in fear of using up too much electricity and will end up reading by the light of head-torch rather than risk needing a jump start the next day.

    Van Battery Types
    There are two types of vehicle battery - starter batteries and 'second' batteries (second batteries are also known as 'leisure' batteries and 'deep cycle' batteries). Starter batteries are designed to supply large amounts of power in short bursts - specifically to start the engine; starter batteries are not designed to get regularly run down - they function best when the engine starts first time and the alternator then tops them straight back up.
    Leisure batteries on the other hand are designed to function well when you run them almost completely down time after time - this is why they are called 'deep-cycle'.
    Leisure batteries can in an emergency be used to start an engine, but they are primarily designed for extended use by lower power devices.
    Of course you do still need a way of re-charging the leisure battery, so the ideal arrangement involves a system where your van's alternator charges both batteries while you're driving, but only your leisure battery is drawn on whenever the engine isn't running.

    Installing a Leisure Battery

    Firstly, find a good place to store your second battery. First choice is in the engine compartment. Ideally you want to have the leisure battery as close as possible to the starter battery and alternator (making charging more efficient and cutting down on cable routing)
    You also need to think of safety - batteries give out hydrogen when they charge and can potentially leak acid and even blow up.
    So if you need to site the battery inside the van due to lack of space in the engine compartment, you'll need to create a boxed in area keeping the battery isolated from pretty much everything else. In particular, do NOT put the battery right next to the gas! - definitely asking for trouble!

    Battery Wiring and Split Charge Relays

    OK, the wiring for this is actually fairly straightforward, but can be a bit daunting until you get your head round it.
    Firstly, how does the charging work - well, essentially your van's alternator charges your starter battery whenever you're driving, and you want to hook your second battery up so that it gets charged as well. All that’s really needed to achieve this is a big cable running from the positive terminal of the starter battery to the positive terminal of the leisure battery, plus you obviously need to get an earthing cable and connect it between the leisure battery's negative terminal to a good (non-painted) earth bolt somewhere on the body of the van. At the simplest level, this is all the cable you need to get the alternator to charge the battery.
    Unfortunately its not quite as simple as that, because you want to protect both batteries from getting used at the wrong times. One solution to this problem is what’s called a 'Split Charge Relay'. The diagram below sums up a "split charge relay" set-up pretty well...


    The trigger wire for the relay needs to come from the dash warning light wire you are looking for the wire (normally blue) that either comes from the regulator (located behind the air filter) see diagram or from the alternator if it has a internal regulator.



    To check you have the right wire turn the ignition on so that the dash warning light is lit then pull the wire off if the light goes out you have the right wire.
    Some people will tell you to take the feed from the coil my advice is don’t as this will mean the battery’s will be connected together as soon as the ignition is switched on meaning that the starter will take power from the leisure battery.

    Self switching relays
    You can get self switching relays the sense when the main battery is full charge then switches over to charge the leisure battery.
    Personally i dont like the voltage sensing relays as the only charge the leisure battery when the main battery is fully charged. The alternator is rated at 55 amp but it changes the amount of amps it produces according to the load placed on it so charging one battery at a time it will take longer to fully charge both battery's and if your main battery is a bit week it may not even switch over

    Now what do you need.
    to source your own bits i recommend this site .

    Its essential to use the correct size of cable. You will need to know the maximum ‘amps’ each single cable might have to carry and use a cable of more that that rating

    Voltage will ‘drop’ progressively the longer the cable run, this should be taken into consideration when selecting cable size. As a general rule go one size bigger

    I tend to use 4mm2 or 6mm2 rated at 39 and 50 amps

    For further information of relays and testing read this excellent guide.

    Now you have the spiltcharge system in place you can connect the circuits you want to run from the leisure battery.

    I recommend you use a fuse board something like this as it uses the same fuses as the van


    you can mount this where you like and run a cable from the battery to one side of the fuse board then using the correct rated fuse run a cable to your light etc.

    I like to use 2 core cable and have a central earth point by the fuesboard this has several advantages.
    It makes testing easier
    you don’t have to fund a good earth at the light so if its mounted on wood it not a problem
    You don’t have loads of earth points to drill that then can go rusty.

    When running cable make sure it is well secured along it length and if it passes through a metal panel it is protected from abrasion and vibration by using a grommet.
    If in doubt find a electrician who knows vehicles or ask on hear.

    Part 2
    230v mains hook up to follow
    Last edited: Jul 12, 2015
  2. Hmm. You're in Somerset. I'm in Worcester. But my bus is having a roof fitted in Exeter in late-February. Do you do a mobile fitting service? Could you do it in Exeter? How much for the whole job? I quite like the sound of a Sargent unit, posted by a helpful member in another thread. Let me know what you think. Was thinking of fitting it myself but would probably cause a fire knowing me.
    Wills likes this.
  3. Pm sent
  4. Diddymen

    Diddymen Moderator

    great post mate :D
  5. Honky

    Honky Administrator

    Great post. Another TLB award nomination.
  6. Poptop2

    Poptop2 Moderator

    great post dude -- justin time , k+
  7. Missed this first time around. Excellent post Matty.
    Like the idea of using twin core wiring. I've seen a fuse box with a centralised earthing post and wondered why anyone would bring earth wires all the way back to the fuse box. You've answered my question.

    I have a question about the trigger wire for the split charge relay. The dash warning light goes out when the engine's running so why doesn't the relay also switch off, or am I missing something?
  8. The light is wired up different to the rest of the bus. Normally the electrics are all earthed with a switch live but the alternator light is live with a switched earth.
  9. hear you go http://thelatebay.com/index.php?topic=2248.0

    Or the key points
    The charge dash warning light is live on one side of the bulb with the key in the on postion.The outher side of the bulb goes to the regulator (internal or external)in the engine bay and to earth so bring on the light.When the engine is running at a suitable speed the regulator switch's over and puts a Pos supply on the wire to the dash.As the bulb now has a pos on one side and a pos on the outher side the bulb goes out.
  10. Ahh, clever. Witchcraft I say.
  11. The positive / negative swap over was what I wondering about, Cheers Matty K+

    I need and engine running signal, so i'm guessing that using the feed to the dash light to energise the coil in a relay will pull the switch and give me that signal?
  12. Hi Matty
    Excellent post. I've been trying to work out my leisure battery / Zig CF8 set-up since I bought my bus in September. Looking at the wiring I reckon they've not put a heavy enough wire from the leisure battery +ve terminal. I still cant fathom the Zig unit or why it doesnt work at all though! And I'd like to add a mains hookup, too, which I think can also be used to charge up the leisure battery. Think I might call on your services when I've saved some more cash as you're only about 40 miles from me.
    Cheers Dobber
  13. Cheers Matty

    I had already downloaded but think I'm a bit thick with the wiring diagrams!!

  14. Excellent post, it's on my 2013 list of jobs as I've nearly got all the required components...

  15. Parts needed for split charge syatem

    I would use realy R30AF with built in 30amp fuse

    Ref 39. 56/0.30mm, 4mm2, 39amp. cable to the fuse box from the battery and between the battery's

    I like to run 2 core cable from the fuse box a live and a neutral and have a central neutral point near the fuse box
    it also means you dont have to drill for a neutral at every fitting handy for lights fitted in wood.
    CM216 2 32/0.20 (1mm2) 16 5.5mm

    Fuse box
    CL1352 i use this one as the fuses match the van so you only need one type of spare you will need the strip below as well to join the fuses up

    also see

    for 240v information and information on all in one units
    ketbag and Lofty like this.
  16. Woo hoo clear instructions . wish if found this thread way earlier.

    I've been searching for info on split charge relay for ages.

    Getting there. Every days a learning day.
  17. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    If @matty ever leaves TLB there'll be a spate of electrically broken campervans.
    75swampy likes this.
  18. The best thing is not to over complicate or over think it the van electrics are simple basic circles and on off switchs
  19. sANDYbAY

    sANDYbAY On benefits-won't sponsor!

    Wrong, the best thing is to have a Matty. :)
    NatchoNatchoMan likes this.

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