How to wire Split Charge without relays

Firefox

Firefox

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I posted this on another forum in answer to a question so thought I would put it here in case it is useful.

Suitable for self builders who want a simple approach. All the loads are on two wire return like boat wiring. So you don't have return via the body and more potential for earth faults.


  • Yes it has been tested
  • Yes it all works
  • No my van or leisure vehicles have not blown up in 20 years of using this method.
  • No I never forget to set the switches. I switch A and B together so I can't switch on the Caravan electrics without isolating the leisure batteries. If you feel you will be forgetful and not put the vehicle on charge when going on a run then add a dashboard buzzer on another switch to remind you :p
It's a very simple way of wiring up charging and distribution without using relays, Zigs or anything like that.

All the parts you can buy at DIY stores, Maplins, Halfords etc so no need to visit scambay or any specialist (read "premium price") suppliers.
 
Neat.
But, silly question, why not use a split-charge relay for Voltage sensitive switch?
Having manual switches is an accident waiting to happen, though I'm glad to see some heavy duty cables! :)
I bought a VSS from eBay for a fiver and a relay is only a couple of quid. Probably cheaper to do that and use lower Amp cable/fuses.
Nice to see a hand drawn diagram!


PS - I also have a fuse between battery +, and also at the battery end of the main live cable at the battery end as otherwise if the cable shorts it would take the leisure battery with it (Mine runs protected but under metal seats etc - so good to be safe)

PPS - you have a good way to charge the vehicle battery when on hookup too - I was thinking of adding a bypass switch for that reason... (I bought a regulated 12v-->12v charger instead)
 
A lot of the time I don't want to charge off the alternator. If I am going from hook up to hook up for example. In fact my smart charger gives a better charge than the alternator, and if I let the alternator have a go it dulls the charge slightly.

My system also allows the leisure batteries to be used for starting. (apparently OK with my brand of "leisure" battery suggesting they are only slightly beefed up starters!) Or I can use the engine battery on the leisure circuit for a short time if needed. I wired my other van I built with a relay but it blew after a couple of years, and I've always had the switch in my car camping conversions, so I guess I get used to it.

I agree with you though, I would recommend a relay for anyone who is a bit forgetful or just wants a plug and play system. It's just to let people know there is an alternative out there :cool:

The other thing I found is some people speak of "split charge relay" with some mystique as though it is a special component which apportions the charge where it is needed. In reality it is just an on/off switch! You'd of course need one of those special boxes of tricks by Stirling or similar for effective charging management.
 
Techno100 said:
I like the presentation of Clive Mott's drawings Clive`s
Click to expand...
Thanks for the link. I think my wiring or any of the wiring diagrams can prove confusing at first, but If people are having problems then print them out and spend an hour studying with highlighter pens following the currents from the battery to the loads/appliances. Remember, a relay is just a switch which control one current with another current via an electromagnet which makes the contact.
 
""In fact my smart charger gives a better charge than the alternator, and if I let the alternator have a go it dulls the charge slightly.""

Correct as you are linking a 85ah engine battery to 2 x 110ah leisure batteries when engaging your charging switch. The reason the smart charger is putting in a better charge is that it knows to "Fill" your 110ah batteries to full. When your alternator is doing the work, it see's the lower 85ah battery as the cut off point, thus both your leisure batteries will not be fully charged.
B2B chargers can overcome this with a clever pit of software programming, but are by no means cheap. See the link below for info;

Sterling Power Products: Battery-to-Battery Charger Information

There is no doubt that a smart charger is the best thing when on Hook-up (I too have a Smart Charger and turned off the Sargent unit fitted to my Swift), but as I also use the van off Hook-up alot, I would like to get the best out of the alternator if I can.
 
Firefox said:
Bump
Click to expand...

Cheers for the bump, although I'm already panicking about words such as relay, smart charger, inverter, split charge relay etc :scared:

But I think the hand drawn diagram actually makes it less daunting, and appeals to my artistic (as opposed to scientific) nature, so I will sit down with it tonight with highlighters etc, stand by for some "What doesn this mean?" questions later.
 
i prefer the smartcom relay,its cheap,very easy to fit and pretty much designed for electricity morons,has simple instructions and seperate connections for the fridge and leisure battery
 
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