jremington:
This document says you must charge the battery at constant current of half the ah rating which is not correct. it sais that if a battery is 100ah you must charge at 50A.
If you are referring to this link: http://www.exide.com/Media/files/Downloads/TransAmer/Battery%20Care%20and%20Maintenance/Battery%20Charging%20&%20Storage%20Guidelines%20%205_9_13.pdf , I don't see any such statement therein.
It's stated in the "Bulk charging" column, but that's stating the maximum charge current. I'm assuming they're stating that it's unsafe (explosion, etc.) to charge at a higher rate. "It is typically only used in applications that need rapid recovery for deeply discharged batteries." So if you're stranded in your car with a dead alternator then anticipate no less than 2 hrs to recharge the battery.