I'm using a 'universal car laptop adapter' for charging 4 cells. It can go to 7 cells within spec and possibly more. Cheap on ebay (£8 in the UK). Minimum modifications are to bypass the voltage setting switch with a trimpot and to change the leads. Other things to consider are a meter to see what's happening, a new container for better cooling and reverse polarity protection.
Technically these are 'wattage-limited' switch-mode power supplies that boost 12v. So they can only be used to charge 4 or more cells. Two sizes are available, 80 and 120W. The 80W version with 4 cells starts at around 10A and drops to about 6A as the pack voltage rises (80W / 14.4v = 5.5A). These currents are ideal for these cells. I describe the basic unit on my site and will update it with my A123 experiences within a week.
http://www.flyelectric.ukgateway.net...er.htm#laptop1
Regards, David.