Split-charge relay - More than 50amps can flow between the engine battery and your leisure battery, so always get a relay that is rated at 50amps or more.   Preferably 75 or 100 amps.  Many relays sold on eBay are 30amps and designed for systems on cars, and not for connecting heavy duty batteries.


Comments (206)

  • transitvanman's picture

    hi i just got a transit conversion camper..it does carver p4 heating system on board but we cant seem to get it working ie getting the lights on at switch to control the settings,,unsure if its just wired up for on site (240),all the wiring seems to be in place and conversion looks pretty new any comments would be freat many thanks stevie

    Aug 17, 2009
  • David in Washington's picture

    We are trying to build a campervan and get electricity to the rear of the van to run microwave/fridge, etc. I've found that the inverters would work perfectly IF they had a battery backup built in. Does such a thing exist?

    Sep 05, 2009
  • Darren's picture

    Hi David

    I am not aware of inverters with a battery backup built in. Instead you need to build a leisure battery system. Then run the inverter from the leisure battery system.
    Charge the leisure batter from the engine, using a split-charge relay.

    Be warned though, that microwave ovens use a lot of energy, and you're likely to need more than 1 battery to hold enough charge to run the oven for some time.

    Sep 15, 2009
  • Anonymous's picture
    Anonymous (not verified)

    You can hook a three way switch up to your battery leads, so long as you have a beefy enough alternator, you can charge up the three batteries at once. What I would do, is hook up two 12 V deep cycle batteries, preferably optima yellow tops, in parallel in the rear of your van. Set up a switch that is load break rated for whatever the output of your alternator is. After you start you start your vehicle, switch from your starter battery to the two backup batteries in the rear, try not to run them all together in parallel. The alternator has circuitry to correclty charge a lead acid battery at ONE state of charge. Charging you backup and starter batteries will confuse this charging circuit. You can get s switch at marine supply places

    Oct 16, 2009
  • Stuart P's picture

    I want to run PC type speakers (Logitech) powered from from the 300watt inverter, but get a terrible and anoying "hum"
    This is just a cheapo inverter and I would be grateful if anyone can point me in the right direction, to be able to use my Ipod this way when camping would be the "icing on the cake"
    Best regards

    Oct 11, 2009
  • Shaun W's picture

    Hi Stuart. Probably the reason for the speakers buzzing is that your inverter isn't a pure sine wave type. These are more expensive but deliver the electricity the same way your house electric works. Hope this helps!

    Aug 03, 2014
  • Anonymous's picture
    Anonymous (not verified)

    Hello there!
    I have a recently aquired 1971 Mercedes Hanomag L206D! I Installed 2 175W Suntech solar panels like a catwalk on the roof, I have that hooked to a Solar Boost 30 amp (oversized, I know, but free) charge controller and two optima D34 Yellow Tops in series so I have a 24 V DC system. Found a great little swamp cooler and some low current LED rope lights. I can run both all day and all night. I could probably run a couple other appliances depending on thier power for a short while, I estimate that the system can produce up the 1 kWh per day. I am about to gut the interior and add a small kitchenette and a few small cabinets. I'll post pictures!

    Oct 16, 2009
  • JimmyTS's picture

    Hi There

    Please can someone advise what cabling I need for my van. I will be installing a leisure battery (which is located in the engine area) and will be running small loading appliances such as lights and a socket to charge a laptop and mobile phone etc. I will also have a water pump. Do I need to run a negative cable from the leisure battery or can I just connect a cable to the metal frame of the van? Also what size cable do I need?

    Oct 16, 2009


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