What is this and how does it work?

So I have a 110 defender with a Nissan FD35 engine, started with a 24V starter motor. Whilst all the electrics of the landy are run on 12V. This little gizmo was attached to 2 batteries under the seatbox before I stripped the defender down and I am now 'crossing the bridge' so to speak with the 24V starter motor problem.
I know this must split the charge or step-down the voltage for the electrics but I don't have a clue how to fit it/wire it or how it works. Any light on the matter is most appreciated.

P.S. The engine runs just fine so no, I'm not going to 'just swap it out for a 200tdi' and yes I know the engine is from a Cabstar and I have checked with dealerships and Nissan forums and found nothing.

Looks like a typical flux capicitor to me,

Failing that it's a switch over relay for the 12/24v

Any idea where I might find some information on how to wire it up?

Sorry if this is stupid question, but do you have a 24v altinator fitted and both batteries are 12v?

Mcclegend said:

Sorry if this is stupid question, but do you have a 24v altinator fitted and both batteries are 12v?

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they are wired in series making 24v ,it was common years ago for 12v tractors to run 2 x 6 v batteries in the same way

Mcclegend said:

Sorry if this is stupid question, but do you have a 24v altinator fitted and both batteries are 12v?

Click to expand...

Yes, alternator works off 24V as does the starter motor, everything else is standard. Looked for a 12V starter motor that would possibly fit the engine but no luck, so gonna have to try and whack this thing on and try to wire it somehow...

Is this it do you think

http://www.genr8.net.au/uploads/file/47.pdf

Mcclegend said:

Is this it do you think

http://www.genr8.net.au/uploads/file/47.pdf

Click to expand...

Ah, this looks like it! Thanks very much!

When I saw the title of this thread I was hoping to see a picture of a steering wheel.

I'm still struggling with this one are you sure that the altinator is 24v. It has kept me up most of the night.

Mcclegend said:

I'm still struggling with this one are you sure that the altinator is 24v. It has kept me up most of the night.

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I'm having a slightly educated guess here but,...........based on the idea that a battery is a number of cells connected in series. If you then take two 12v batteries and connect them in series, you have made a big 24v battery. You would then need an alternator pushing out 24v+ to connect across it. Just as you would a 12v+ alternator for a 12v battery. Could be wrong though

As said above it is a 12V - 24V relay module, i.e. series or parallel relay that can link the batteries to get 24V for the starter by linking the batteries in series out to the starter ONLY while the rest of the system sits at 12V, it then reconnects the second battery in parallel to the rest of the system to keep the two batteries charged equally.

If you search under 24V starter and my username you will see circuit drawings of how they work (I had actually designed this circuit for someone to make a unit like you show).

It's really quite simple when you see it - as for how to wire it up, if I could get it in front of my with a multi-meter and a 12V supply I could work it out. Basically you need to find the main terminals and the battery connections, then work out what terminals go live/dead when it gets switched - it could also be very simple in that it takes 2 battery feed and simply has one output and all the magic goes on inside - but that would not work well as the whole system would get 24V - it is more likely to simply create 24V for the starter.

The question that has arisen regarding the alternator is interesting, the alternator in these setups should be 12V because the batteries in "normal" mode are just two 12V batteries in parallel and get charged as such.

SOME people did cock this conversion up and would connect two batteries in series to make 24V, and then charged them with a 24V alternator in parallel, but connected the vehicle across only one battery to give it 12V but this lead to one battery constantly being charged at a lower rate and caused early battery failure. BUT, if you had this then you would not need the series/parallel unit.

You ought to have, 2 batteries, 24V starter and a 12V alternator and the relay unit.

A while ago I had a 110 defender with Nissan 3ltr it had 12v altenator\24v starter and 24v glowplugs 2x12v batteries never got round to sorting electrics properly just swapped batteries round and it was in Scotland as well drove it down here and back and it never missed a beat super smooth.

12v alternator and everything becomes clear, that's the bit I was struggling with.

Remember now starter and plugs came from Samurai Engineering as there were none with it they advertised in LRO