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Dual Alternators


chadler

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The 200tdi is being fitted into the truck as we speak, and having researched different options available for the electrical system, i want to avoid split charging and go for a dual alternator system. My poking around has revealed that people tend to like big ampage numbers when choosing a second alternator and go for marelli 100amp ones, but in in the interests of commonality i'd like to fit an identical alternator to the existing one. A few questions therefore:

1) What alternator is fitted to my 200tdi, and does anyone have another one they would flog me?

2)Is there a standard bracket available to mount it to the air-con compressor mounting holes available, or does someone have specs for the mounting needed?

3)Wiring it up- Thick wire to second battery obviously, but i hear the small wire goes through an ignition switched relay and then through a spare dash-light so that the VSR can detect the charge state of the appropriate battery, rather then charging the second battery according the VSR detection of the first... Is this right? wiring diagrams please!

4)Part numbers of the belt/pulley would be greatly appreciated

5)if anyone has done this could they post pictures please?

I'll post pictures of my auxilliary fusebox setup when i get the vehicle back, as i'm quite chuffed with it, and will also do a tech article on this installation with pictures if people are interested? I'll be doing two vehicles in our fleet to this spec, so i should know what i'm doing by the end of it!

thanks in advance

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Hi.

The second alternator needs 'start up' current from a battery (via an 'ign' light) when you start the engine, but if you leave this permanently connected to battery 2 it will drain the battery while the engine is not running. The obvious solution is to source the start-up current from an ignition switched source, which could be the same point that alternator 1's start up current is sourced from. This connection has nothing to do with voltage sensing, it is there to 'excite' the alternator's internal magnetic fields until the alt is producing current, at which point it provides it's own excitation. Alternator 2 needs to be fed start-up current via it's own 'ign' light, don't connect the two start-up inputs directly together. The tag is usually marked 'ind' and is connected to a brown / yellow wire.

I understand that the 'R' of ACR refers to remote voltage sensing, rather than machine sensing, so it needs to have the voltage sense wire going to battery 2 along with the output wire.

I don't know if / how we can post diagrams.

Don

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This is looking interresting. Pics and part numbers would be of interrest to a lot of us I'm sure.

Re posting pics there is a good thread Steve has made sticky in the Disco forum.

Did 200's come with aircon? I'm pretty sure my 200 has the timing case casting to accept an aircon but its not beeen tapped and prepped like my disco?

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Hi all.

Tonk.. my initial reaction to

' if i fit a second alternator, can i just wire it up in parallel to my existing set up? '

was to say something like

'don't even think about it'

but when I came to explain the reasons I couldn't think of any. It is true that the two alternator's voltage regulators are unlikely to be perfectly matched, so one of them will tend to do more work than the other.

It would be good to use the same make and model of alternator (and driving and driven pulley sizes) to help matching.

It would be necessary to connect the alt 2 output and sensing wires to a carefully chosen common point, (ie the point where the original alt meets the rest of the loom), and it would be sensible to use the same length and thickness of wire to keep the wiring losses matched.

Running the engine with the battery disconnected would be a seriously bad idea, but then, it always is.

It still sounds 'wrong', but I don't know why... is there anyone out there who knows any other problems ?.

Is there anyone out there who knows any ADVANTAGES of connecting two small alternators together over fitting one big alternator, other than having a 'back-up' ?.

Has anyone considered fitting a second alternator that is usually not being driven (no belt) but can be brought into use when required by fitting a belt to a pulley arrangement that would drive the alternator at full alternator speed while the vehicle engine is only running at a brisk tick over ?. Care would be needed as that alternator would be damaged if the engine revs were increased so that the second alternator was run too fast.

Don

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well i was thinkin of fitting the same alternator as already on there and same size pulleys.

was going to have 2 different signal charge lights on dash cos these i think should be kept separate and then i'd know if one died.

any advantage in having a shut off on one alternator so only one charged most of the time? but have 2 working when competing all day?

just thinkin out loud really

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well i've been told that if u have 2 alternators on the same circuit then one will only charge, at lower revs especially. this is because they are voltage sensing and if one is charging then the other wont bother. sound about right?

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Hi again.

Yes, sounds about right, but don't see that it would be a problem, two 60A alts would still effectively give you a 120A alt.

Just to recap from my earlier post :

It is true that the two alternator's voltage regulators are unlikely to be perfectly matched, so one of them will tend to do more work than the other.

It would be good to use the same make and model of alternator (and driving and driven pulley sizes) to help matching.

It would be necessary to connect the alt 2 output and sensing wires to a carefully chosen common point, (ie the point where the original alt meets the rest of the loom), and it would be sensible to use the same length and thickness of wire to keep the wiring losses matched. (for balancing purposes)

Don

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You could, if you used a second battery (for winching etc). Wire the 2nd alternator completely seperate from the main battery. Connect the winch to a separate battery wired into the second alternator, it would then always have something to do.

The clever bit, would be to earth the alternator and 2nd battery through the body work, but the live would only come from the 2nd battery (along with a switched warning light) to the alternator.

Between the main and 2nd battery connect a suitably sized lead with a cut-off switch (motorsport style). If you flattened one battery, or either of the alternators failed, the switch could be turned on, turning the system into a twin battery system. In the event of both batteries requiring quick charge, then again, the switch could be closed to allow both alternators to charge the batteries!

NOTE: never run the second alternator without a warning lamp feed though, because the alternator will create current as the engine is running, but will have nowhere to put it, causing internal failure of the voltage regulator!

When I get home later I'll try to draw up a diagram of my ramblings!!

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Guest diesel_jim

Sorry for the delay in replying to this thread.. i'm in Spain!

i have twin alternators on my 300Tdi 90, also had the same setup on my V8 and 200Tdi.

for the 300 it's pretty easy as all the parts are available off the shelf, using a combination of air conditioning and military wolf XD parts.

i made the alternator bracket myself, as the military one wouldn't fit the 130A ex disco one i fitted, but that was only a flat 5mm plate and 4 tags welded on.

the wiring is easy....

run a LARGE cable from the second alternator back to the second battery. run the "sense" (or "warning light") cable back to the dashboard area.

on all 90/110's there is a spare symbol on the right hand lower side of the warning light cluster. it's the one used for miltary FFR's and it shows a battery with "24v" in it, i use this just because it's a battery symbol. take the sense wire, and connect it to one side of this bulb (the very small red coloured speaker crimp connectors work a treat!), then take the other connection on the bulb unit and connect it into a spotlight relay. you need to connect it to one of the switch contacts. the other switch contact goes back to the second battery positive terminal.

then, take a feed off of the ignition switch that is powered by position 2 of the ignition (the position when the oil pressure light and charge light comes on). this feed goes to the coil side of the relay, and the other coil terminal goes to earth, so when you turn the ignition on, it energises the relay and closes the contacts.

job done! /some/ people take the second alternator sense wire and connect it to the ignition switch directly, this won't work properly as the alternator will be reading the voltage of the main battery, wilst feeding the charge onto the second battery.

as for connecting both alternatord together, yes, this does work. i've got a link switch between both batteries on mine, so if my main one goes flat, i can still start the engine, and if i link it when the engine is running, i get a combined battery amperage of 1600amps (2x 800a optimas) and 230 amps of charging power (130a second + 100a main) from the alternators.

I'm back in the UK in a couple of weeks, so if anyone wants some pics then, then shout!

Jamie

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Hi all.

I suspect that there is some confusion over terminology here.

The 'ind' connection [short for 'indicator'] (Lucas) [or 'D+' (Bosch)] provides initial exitation current which gets the alternator's internal magnetic fields started

This INPUT is fed through a bulb which glows while the alternator is drawing exitation current, but goes off when the alternator has started to generate current and is able to provide it's own exitation current.

The 'ind' connection has no voltage sensing function.

The bulb in the circuit is sometimes described as 'warning light' as it will come on if the alternator stops generating current, for example when the fan belt breaks.

The 'Sense' input is (theoretically) used on 'battery sensing' alternators to bypass any wiring voltage drops.

All of the alternators I have seen have been 'machine sensing', and have not needed a sense wire.

Most older alternators (eg all ACRs) that I have seen have had a third terminal that has actually been internally 'strapped' to the output terminal, and have been connected in parallel with the output wire.

I may not be up-to-date with the very latest alternators, does anyone know differently ?.

Don

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Ok, Further to investigations....

It appears that no defender 200tdis are drilled and tapped for the air-con mounting, but some surfing has turned up this gem of a site (to whose authors i give full credit....) http://www.ifwdc.com/tech/winchpump/winchpump.html

more specifically

If milemaker recommend this sort of mounting then it must be up to the job. What i'm wondering is, since there has been such interest in this thread, does anyone think that there might be sufficient interest for someone to make up a batch of these mounts but adapted for alternators? If any of you welding-gods out there are up the challenge then i lay down my gauntlet!

Cheers

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i thought about going for a second alternator but as i don't have a winch i used a 100amp VSR to split charge a pair of 100AH leisure batteries, i also have a second wire with a 'red key switch' running back to the engine start battery so if that ever goes flat i can put the whole lot into parallel and jump start myself.

all my accessories run from a second fuse box, this includes CD player, amp, fridge, extra lights, etc... its worked realy well as i can flatten the leisure batteries and still start the truck...

i'm selling the 110 in a few weeks time and will be removing the whole lot in order to fit it to my new motor....

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