Split charging system questions

Hello all

My Jimny has a dual battery set up installed by the previous owner

It seems to work but the battery light stays on when the car is running does anyone have any pointers on where to check

The car starts no battery drain issues etc it just annoys me as it’s not meant to be on!

To clarify it’s the car dash battery alternator light

If the ignition warning light is on, then either there is a short to ground on the L wire to the 3 pin plug on the alternator. or the alternator regulator is faulty.

There isn't an external regulator is there, for "super fast charging"? I've only ever seen them on boats.
I take it that that display reads between 13 & 14 V when running.

Going down the same line of thought as Facade, you might want to confirm that the previous owner didn't convert to a higher amp alternator when he went with the dual battery setup. If he did, and everything else is working properly, then it would likely be the L wire.

Bit of update the system is charging both batteries and pushing out enough volts the light is on dim not full brightness

Seems to be working, I'd keep an eye on that voltage monitor and be prepared to buy a new alternator.
Tbh, I'd likely fit an alternator anyway, but I'd worry it was going to fail and let me down, and they aren't cheap.

The dash looks like a late model, so the ignition warning light is an LED, it can't light up if the ignition feed is low due to a bad earth or dirty ignition switch like a bulb can, it must be the regulator pack or a diode in the alternator.

You could try unplugging the multiplug on the alternator and switch on the ignition- the light should not come on, if it comes on dim there is a load/partial short on the L wire.