They should charge to 14.4v (during absorbtion) and float at 13.25 or somewhat higher with the charger hooked up. Unplugged and resting they should settle back to about 12.8 or so. Not sure if it's the battery, or the charger or what you mean by "charge to"
If you can do spec gravities what specifically do you mean by 10 points?
Generally, a cell is bad if it is off the average of the bank by more than .05 SG units. so if you one cell is of by .20 then it does not meet that criteria.
Example if the average of all 6 cells in your bank is 1.265 and one of the cell is below 1.215, then it is suspect. Note that this only applies to one cell. The other rule of thumb is of you can't charge a battery bank to 75% or more, then it is probably needing replaced.
Open Circuit Approximate Average Cell
Voltage State-of-charge Specific Gravity
12.65 100% 1.265
12.45 75% 1.225
12.24 50% 1.190
12.06 25% 1.155
11.89 Discharged 1.120
2007 Chevy 2500HD Classic LBZ Duramax/Allison (Stock)
2005 Bigfoot 1500C8.2 AWESOME