X-Eng Split Charge Unit

The Badger said:

I've got mine wired so they only show a reading when the ignition is on, and then its the batt voltage shown, I'll try and find my wiring diagram of how someone told me how to do it...

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Yeah, got that bit.

Basically, there's three "states":
Ignition off - both voltmeters off
Ignition on/engine not running - each voltmeter displays the voltage for its respective battery.
Ignition on/engine running - both voltmeters display the charging voltage, i.e. what the alternator is putting out.

Thanks Trewey - just wanted to make sure I wasn't going mad.

Looking at the wiring diagram on X-Eng site am I right in assuming that when the ignition is on (ie engine running) the two batteries are effectively connected in parallel via the relay?
With a winch connected to the second batt and the engine off you only draw winch current from the second battery as the relay isolates your main batt. So far so good as your main batt is protected allowing you to start the vehicle.

What happens if you leave the engine running and operate the winch? Surely you will draw current from both batts through the relay (assuming it is man enough) and eventually drag both down despite the alternator output? I guess for short bursts this would not be an issue or am I missing something?

I ask this as I'm no expert at electrickery and just want to understand the pros and cons of a split charge system.

The x eng kit comes with everything you need to fit the split charge system, Relay,connecting wires and a good length of orange wire and some scotch lock(use at your own peril) You have to add an earth connection yourself.
It's a good piece of kit, With most 300 Tdi you have to run the switching wire to a + supply as you cant tap in to the battery warning light, I choose to to solder mine on to the stereo output at the fuse box, as there is no power going to it when you engage the starter. I run my 2 Numax batteries which are squeezed under the seat with a cut of switch and the x eng split relay, it does fit,

I have drowned it many of times going through rivers etc and it's still going strong,

I have run a seperate fuse box (6 connector one) and mounted it behind the passanger seat to run all of the accesories.

Shifty, you're absolutely right. There are systems out there which will isolate one battery or the other, so you don't discharge both batteries if the alternator can't keep up - but the basic split charge system (which is all the X-Eng one is) doesn't do that.

Thanks for that. At least my school boy understanding of the set up was not far wrong. I realise that for the money it is a decent, easy fit, set up which will suit basic installs for accessories etc. Not having a winch I'm not too bothered but it would be nice to run an invertor and my kids video players without risking my starter battery which I think the X-Eng would do. I also understand that if you spend mega bucks you could get an all singing all dancing splitter.
I reckon I could make one out of an old starter solenoid (used as the relay) but maybe they are not designed for prolonged operation? What about a heated rear window relay? Just thinking out loud. I dont really squeak when I walk - honest.

Relays really aren't that expensive, Shifty!
For under a tenner you can get a 70A relay off fleabay. Then just wire up the same as the X-Eng one. I'm putting a fuse in-line between the relay and each battery to be on the safe side.

In theory, if the engine was running but your alternator couldn't keep up with demand, you'd run both batteries down - but a voltmeter/charging light will tell you if that's the case. And if the engine isn't running, your starter battery will be protected (assuming you've hooked up the accessories to the auxilliary battery).

Would you see the volt meters and charge light if you was outside with winch remote in your hand, just a thought !

Hamsterberg said:

Would you see the volt meters and charge light if you was outside with winch remote in your hand, just a thought !

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Nope - but Shifty isn't considering a split-charge system to drive a winch.

Correct.

instantsquid said:

Nope - but Shifty isn't considering a split-charge system to drive a winch.

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True but i might be !!
Ive got a few mates in the boat building game will see what they come up with..

As mentioned earlier, there are more sophisticated setups that will allow you to isolate the batteries completely. This is overkill for my requirements but I can see why they would be of use to others.

Some guys in the club dont have second batteries fitted to power there winch, and sometimes there winches are going for ages, Sometimes we do a lot of stopping so we can park on hills in gear while were deciding on recoveries and there batteries have never let them down.

I prefer the second battery with the x eng split charge system, Yeah effectavily you could draw from both batteries but watching the volt gauge on the dash when winching i have never had the volts drop to much or the battery warning light come on

Given that the X-Eng split-charge unit has a 180A relay in it, what size cable does it come with? The photo doesn't look like it's particularly meaty (maybe 30A cable).

Sorry to bring up an old thread but I've just bought a X-Eng split charge relay and I was thinking would it be possible to put an isolator switch on the alternator - relay wire, so that you can have the engine running, and the relay will only draw power from the aux battery if you were winching, for example? At least then if for some unknown reason if the main starter battery does go flat, you still have the engine running, just a thought

instantsquid said:

Given that the X-Eng split-charge unit has a 180A relay in it, what size cable does it come with? The photo doesn't look like it's particularly meaty (maybe 30A cable).

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The cable I got with it is Hi-flex 16mm2, rated to 110A

Dave90 said:

Sorry to bring up an old thread but I've just bought a X-Eng split charge relay and I was thinking would it be possible to put an isolator switch on the alternator - relay wire, so that you can have the engine running, and the relay will only draw power from the aux battery if you were winching, for example? At least then if for some unknown reason if the main starter battery does go flat, you still have the engine running, just a thought



The cable I got with it is Hi-flex 16mm2, rated to 110A

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Thought the whole idea of a split charge system was to disconnect the main battery if the voltage started to drop why complicate things

redhand said:

Thought the whole idea of a split charge system was to disconnect the main battery if the voltage started to drop why complicate things

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Yeah Wasn't going to do it myself, just wondering if the principle would work?