Battery

Quick facts :

• healthy battery shows a 12,6 to 12,8 volts charge
  
• To fully charge a battery it requires 7.5 amps for 36 hours.
• Longest battery life is at 95% charge, not 100%

Gathering infos on the subject here ...

Can a battery be fully charged with alternator ?
From RR forum Australia :
Don't rely on the alternator to charge a 50 % charged battery from a jump start. The alternator will charge to about 80 % only.
This happens because batteries have an internal resistance. So to charge a battery to 12 volts it needs more voltage. The alternator goes to 14 volts and holds it supplying more amps as electrical stuff is used, not more volts.
To charge to 12.6 volts which is 100% battery charge needs 15 volts. At best an alternator goes to 14.6. To charge to 95% (which the best percentage for longest battery life) would take a 100 miles of driving.
A 50% charge is not 6 volts. 6 volts is about 10% charge. 11 volts is about 50 %. Check lead acid batteries on the web, for the proper figures and explanation.