Twin Alternators

[white90]

you need a decent bracket to mount the alternator first, then pulleys... don't be tempted to use the cheaper A/C pulleys, go get the military spec wolf pulleys, they have a dust cap that makes the bearings last much longer!

the large output cable goes straight to your second battery. the smaller "sense" wire goes to your dash, through the warning light bulb (i used the 24V symbol as it has a battery picture on it!) then through the contacts of a small relay (a spotlight relay is ideal), then to the positive of your second battery.

then... you take an ignition feed (position 2 ignition, not the first one where the heater and radio come on), and wire it through the coil of the freshly fitted relay.

this way, when you turn the ignition "on", the 24v light (or whatever you use) will illuminate, as the coil energises and closes the contacts of the relay,allowing the alternator to sense the voltage of the second battery (if you just wire the warning light to any ignition feed you find behind your dash, the alternator will charge the second battery OK, but it'll be reading the voltage off of your original "main" battery.

parts you'll need (using all the military bits and including the alternator bracket...although this only fits certain alternators, my 130a ex V8 disco one i had to make up one.

BH 116131 x2 Bolt

ERR 5870 Mounting Brkt. alternator £74.56

ERR 6005 Drive belt £9.46

ERR 7295 Pulley, ancillary £17.18

ERR 7297 Cover £0.69

ERR 7298 Flinger, oil £1.08

ERR 7387 Tensioner

FS 108257L x3 Bolts, fixing

FS 110301L x4 Screw, flanged £0.51

NY 116041L x2 Nut

the pulleys look all the same as the air conditioning ones, in fact, the tensioner bit is the same part, it's just the bearings themselves have small covers (the "flinger" bit is one of these, it's a concave washer thing that the central fixing bolt goes through to hold it in place)

I used an AC fan belt originally, but since i changed the alternator i had to use a different one. i just went to my local autofactors and grabbed a handful of belts and tried them in the carpark! then bought 2!

The lower crank pulley already has the extra space for the second belt, so it just slips straight over (after you've removed the main fanbelt). it's the "narrow" serpentine belt you need, about 5 ribs in it, as opposed to the wide 9-ish rib that the main one uses.