I fitted my first split charge system to an Austin 1800, back in about
1969, when I replaced the dynamo with a Lucas 11ac alternator.  It
used a Lucas 4BD twin diode unit.

I've now got a 2002MY Defender 130 and have bought an electronic low
volt drop split charge unit, but when I came to fit it found a problem
with the Td5 standard wiring.

I expected a medium thickness brown wire from the alternator direct to
the battery, which I was going to cut and insert the split charge
unit.  But the brown wire does not go directly from alternator to
battery.  It goes to the battery via the ECU wiring mass under the rhs
seat, so putting what is effectively a diode in the battery wire will
isolate the ECU wiring!

Anyone any experience of the actual wiring details?

Web Rover says that all Td5 engines in are equipped with a combined
120 amp alternator and vacuum pump, but without removing much of the
plastic cover trim it's difficult to see the wiring to the alternator.

I had also hoped to buy a special controller to increase the control
voltage level to fully charge auxiliary batteries.

Any help would be welcome.

Reg.