If you plan on continuing to use that charger, you'll probably need a BMS. The reason the Black and decker works is because it only charges to about 98 % of the battery capacity which means you have some room for error. Read the other thread "looking for recommendation" if you haven't already. I just don't want to see any of your cells damaged. You could probably make your current configuration work with a cheap BMS like this:

http://www.hightekbikes.com/BMS.html

Or getting rid of that charger and getting a different one.