I remember someone posting about there battery light being on dim all the time,even after changing the wiring, alternator and battery,
I've had the same problem on a few cars in the past and not bothered about it!
on my current car the batt light has been on dimly, but come on bright sometimes, after trying a few alternators, and changing the wiring, the fookin thing still done it!!
I've found it to be the FAT red wire in the plug between the barrel and wiring loom, it had melted!!after repair, the light aint come on since
hope this helps someone