I bought my 5500 second-hand from ebay. When I got it, I found that when I plugged the charger in, the charging light would go off after around 20 mins. Obviously, the battery would wear down in no time at all.
I got one of the 1800mAh batteries from Lauter the other day, and now the battery light goes off after about 45 mins of charging. Pulling the AC adapter out and putting it back in will bring the battery light back on for a few mninutes, but then it goes off again.
Could there be a problem with the charging circuit, or could it be that I need to condition the new bigger battery with a few charge/discharge cycles?