Check the cable that goes from the alternator to the battery. The cable should be of reasonable thickness with good thick stranded conductors. Probably around 10 AWG. If you go to the auto shop, I think they sell proper alternator cable for the purpose.
I had a problem once with mine. There was a nylon connector half way along which had corroded a fair bit and the thing was barely charging at all. Went to the shop and got a new length of cable and no problem since.
That would be the number one thing I'd be definately replacing!
:hit:
