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Twin Alternator Set up-Disco 200Tdi (in 90)

90 Mellis

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Morning-The next in my long list of things to do is sort the charging system on the Challenge Truck build, done some searching and have some rough ideas.

Engine is a Disco 200Tdi fitted into 90. Winches are 1 maybe 2 8274's. Budget......not very much!!lol

Thinking along the lines of using a second alternator in the A/C Pump position and this charging two batteries purely for the Winch/winches.Leaving the original battery for 'normal things'.

Am I heading in the right direction?! What 2nd alternator size are people using, recommended make/size of battery, cables?!

If anybody has pics of there 200Tdi Twin Alternator set up, that would be v.useful!!

Thanks in advance

Mike Ellis

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Guest diesel_jim

I did this on my old 200 (and then on my 300's and several mates V8's)

you'll need to fabricate a bracket to mount the alternator, but it's only a piece of flat plate and some lugs to bolt the alternator to. some careful measuring so that the alternator sits true and parallel to the belt, and "sticks out" in the right place for the belt to run on the pulley.

The second alternator, be it 12 or 24v, can safely share the same "earth" of the vehicle, no issue there.

run the large charge wire back to the second battery.

take the WL (warning light) wire back to the dash, through a 12v bulb (i usually use the lower RH bulb on defender warning binnacles... it shows a battery and 24v on it, meant for military FFR applications, but the symbol is correct and it looks fine)

after the warning light, take the wire through the contacts of a small relay (like a spotlight relay), the normally open contacts, and then down to the +ve of your second battery.

Then, get an ignition fed live (for position 2, when all the other warning lights come on,oil,battery etc) and take this through the coil of the relay.

So, when you turn the ignition on, the relay energises,closes the contacts and the second alternator can then start sensing from it's own battery (the warning light will come on until you start the engine, then it'll go out just as it shoud).

If you just connect the WL wire from your second alternator directly to the ignition switch, it'll be "sensing" from the wrong battery, and if you don't fit the relay but just connect straight to the second battery, the warning light will always be on.

it's quite simple wiring though.

on my 300 (and 200 i think) i used air conditioning pullies for the belt, although on the 300 they didn't last that long, so i switched to the military FFR pullies, which look almost identical but had little "dust caps" that tap onto the pullies to keep the poo out.

You can use any size alternator you want that'll physically fit in. i had a 130 amp on my 300 (came off of a V8 disco), and seeing as you need to make the mounting bracket, then it doesn't matter what vehicle the alternator comes off of, as you'll just weld it to suit.

on my old 300Tdi: post-130-1216364188_thumb.jpg


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Your more than welcome to come and look at my twin alternator set up again 200Tdi Disco engine and take as many pics as you like...Photobucket seems to have ditched my pics :blink:

I have...

100 Amp for Winch batts

75 Amp for everything else

Batteries can be linked to boost output, or if one alt fails :rolleyes:

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I bought a 120 amp one from a renault laguna that went on Ebay for £15 and piggy-backed it off the A/C pump which is used for onboard air. I just have a simple 2 battery set up with both batteries linked in parallel and both alternators charging the system. Making the mounting for the 2nd alternator was cimple. Finding a V pulley that fitted was more difficult and did involve a very small amount of machining to get one to fit tidy


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Diesel Jim - your way is 100% bang on :) One slight adjustment that i've done to that system, is have a switch so that i can turn that charging system (either alt) off if the need ever arose.

I've not done it on a landrover, but done it on many other vehicles for a different application.

Here is a pair of variably regulated 200A HO alts. I still have all the parts for this setup, alloying me to choose my charge voltage from 13v up to about using a pot (i was running a 16v setup of 24bat's). These 2 alts charged 1 battery system, and then i had another small alternator just to charge a single 12v battery which ran the vehicles electrics.


I have a supplier in the states who supplies these alts and variable regulators, as well as a mate in Derbyshire who customises regulators to similar variable units :) Unfortunately this gear isn't cheap :( the charging system was probably ~ £1k.


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Thanks for all your responses so far, just what I was looking for!!

I've been having a look in 'The Book of Lies' (Haynes) and the A/C Belt tensioner appears to go inside the Belt run allowing clearance for the Water pump?!

Is the tensioner something avaliable off the shelf before I spend ages making one (Can't find them listed on Paddocks)?! Does it replace the plate on the Timing Cover??

Does the Single Vee Belt seem to cope OK with the Alternator pulling full current??

Thanks in advance


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