Battery:
---------
              12V            6V
             -----          ----
Peak Charge  14.40          7.20
Float        13.50          6.75

100%         12.60          6.30
 75%         12.40          6.20

 50%         12.20          6.10
 25%         12.00          6.00

  0%         11.70          5.85

Fully charged when current draw 
is 3% of rated current. Good 12V
car battery will drop to 40mA when
fully charged. Bad one may not drop
beneath 100ma.

Regardless of attemped charge rate, 
going from full discharge to full 
charge takes about 12 hours.



http://www.batteryuniversity.com/parttwo.htm