From the optima site:
OPTIMA® BLUETOP® Charging Information
The following charging methods are recommended to ensure a long battery life. Always use a voltage-regulated charger, with voltage limits set as described below.
BLUETOP® Type: 34M
These batteries are designed for engine starting applications. They are NOT recommended or warranted for use in deep-cycle applications.
Recommended charging information:
Alternator: 13.3 to 15.0 volts, no amperage limit.
Battery Charger: 13.8 to 15.0 volts, 10 amps maximum, approximately for 6-12 hours.
Rapid Recharge: Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.
Float Charge: 13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).
Strictly adhere to all limits.
BLUETOP® Type: D34M / D31M/ D27M
These batteries are dual-purpose. They are designed for engine starting and deep cycling applications, as well as for use in boats with large accessory loads.
Recommended charging information:
Alternator: 13.65 to 15.0 volts, no amperage limit.
Battery Charger: 13.8 to 15.0 volts, 10 amps maximum, approximately for 6-12 hours.
Cyclic Applications: 14.7 volts, no current limit as long as battery temperature remains below 125°F (51.7°C). When current falls below 1 amp, finish with 2 amp constant current for 1 hour for D34M and 3 amp constant current for 1 hour for D27M and D31M.
Rapid Recharge: Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.
Float Charge: 13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).
Strictly adhere to all limits.
Safety Information:
Always wear safety glasses when working with batteries.
Always use a voltage-regulated battery charger with limits set to the above ratings. Overcharging can cause the safety valves to open and battery gasses to escape, resulting in premature failure. These gasses are flammable! You cannot replace water in sealed batteries that have been overcharged. Any battery that becomes very hot or makes a hissing sound while recharging should be disconnected immediately.
Failure to fully charge a battery can result in poor performance and a reduction in capacity.
These guidelines are intended for typical consumer applications. For military, commercial applications, or new equipment design please contact OPTIMA for additional technical information & assistance
http://www.optimabatteries.com/en-us/support/battery-care/charging/
