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split charges


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I'm not claiming to know how it works, I just know that it does.

The hard fact is the relay switches at 13.8v Simples. Take my word for it, don't take my word for it, I don't care because I know that it works.

Why not give them a call and ask them the question??? It would take less effort to pick up the phone than it would to keep speculating on why it won't work (when it does)

Well, that's me bored enough with this now :blink:

Hobson, hope you get yours running, Marks explanation is good, as are the instructions on the X-eng site.

If anyone would like to see my set-up with their own eyes (and meter) and lives in the NE then feel free to PM me. Although my cylinder head cracked yesterday so I don't know if I'll actually be able to start the vehicle - it depends how many bits it's in :ph34r:

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thats ok. the 12s stuff is for caravan setups where you want to be able to run the fridge off the car when towing. not really relavent in a land rover setup as the fridge can be wired striaght onto the aux battery

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Its probably worth pointing out that many landrovers already have a VSR for some of the built in electrics.

Think its used for the heated screen or something on some models, the Disco certainly had one, and the 300tdi loom i baught i'm sure has one too.

Big yellow relay thing.

Can get a part number if anyone is interested?

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  • 3 months later...

Little bit of an update on this thread!

Today I had a visit from a chap with one of these VSR kits installed. As per your photo, the coil of the relay is just connected to the main battery terminals, and does switch on when the vehicle starts charging.

I persuaded him to let me open up the relay (I said I would replace it if I broke it!). Inside, it's just a relay - no electronics, integrated or otherwise. So what is going on?

It seems that one of the wires connecting the relay to the battery is fairly high resistance. If you connect the relay directly to the battery (engine off), the relay energises. If you connect it via the supplied cable, it does not. I've not got a multimeter here to test it properly - but my guess is that the fuse-holder contains a resistor. At <13.8v it does not allow sufficient current to pass and the relay does not energise. Above a certain voltage, it does.

It's a crude way of doing it - but it does appear to work (kind of).

He came to visit to buy an X-Charge because this kit didn't appear to work that well. What appears to be happening is that when you first start the engine, everything is fine. after a few mins idling, the relay switches off. The resistor is heating up and it's resistance increasing to the point the relay switches off. If you rev the engine it switches on again, then off once it has heated some more.

I suggested to him he just wires it up to the alternator and not bother buying an X-Charge. It may just be the combo of battery, alternator and temperature that conspired to make this one behave that way - and I'm sure that others will be fine.

Drift in the sensing voltage is a problem with any VSR. Most are affected by temperature and virtually all by water ingress. They would be fine in a cool, waterproof box - but I felt that it did not justify the risk of damaging your battery when in most of cases, connecting to the alternator does as good a job without the risk.

I think I'll stick with what I've got!


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Sounds scary.

Like you, I'm struggling to work out what they've done! I don't believe just a resistor would be enough. Putting a typical 12V relay on a variable power supply shows that there is quite a bit of hysteresis between the ON voltage and the hold voltage - once the contact has pulled over onto the coil, it takes a lot less force to keep it there.

Potentially, the fuse holder could contain a diac, if the right one could be found, which would hold the relay off till the voltage rises enough, then energise the relay. But this would have no off method, other than dropping the battery voltage off completely. Other than that, I'm at a loss to device any kind of voltage sensing circuit without a ground reference!

I currently have a diac, capacitor and resistor on my notepad, and I'm on the verge of having something that might work as you describe, but....


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I stand by what I said in an earlier post.

The flowery language used in their advert is that of a snake oil salesman.

Simon's investigations would seem to confirm that they are overselling their product's capabilities.

Some on here accused me of being harsh on the seller, but I'm naturally cynical, especially where eBay sellers are concerned.


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To be fair, I'm not sure that the one I looked at was from the same supplier as it was fitted to the truck when the chap bought it.

Without a ground reference, I'm struggling to see a way of achieving better than a resistor. A Zenner Diode is about the only thing I can think might improve it - or an Avalanche Diode (which gives a sharper on/off than a Zenner).


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If you want a decent split charge that handles 80amp continuous and a little more on peak, then get a nagares relay off ebay or another site for ~ £10 (same as x-engs one)they are rated higher but from personal experience I wouldn't push them on a demanding system that needs a contant load. Then just get 1 meter of 25mm2 cable and a few crimp on terminals...walla, a more capable split charge for half the price or for a little more you could protect yourself and the relay from fire risk with a few mega fuses or similar :) A few were commenting on volt drop, if you get a nagares relay, push high current through it for for sustained periods over a few months then look at the voltage across the terminals and you will find a volt drop.

Don't waste your money on a expensive kit for something that is very basic which you can do yourself, but always think what is the worst case scenario and plan all your wiring, relays and fuses for that :)

If you want something that is capable of severe winching, change the relay for an albright solenoid and the wiring for 35mm+. As if you have a battery fail on the end that the winch is connected to the full 400amps will travel through the split charge, not good. Or you could put a system in with a standard relay in parallel if you don't like the idea of keeping a albright active for long periods.

As far as VSRs go though, I really don't see the point when it is so easy to do it the good old fashioned way :)

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