If you are thinking of pulse charging, do not bother (my opinion ).

Constant Voltage is the best way to go. You can start off with a Constant Current but a CV charger sized correctly will do this automatically.

A maximum voltage of 2.4 volts per cell to bring the battery up to charge, then if you want to "float" if for a back up system or something like that, bring the voltage down to around 2.25 volts per cell.

For the "sizing" of the charger, 20 to 25% of the rated capacity is good. A 5 Amp Hour battery would have a current limiter of 1.25 amps. Even if you have a larger say a 12 AH I do not recommend mare than 2 amps. ( If you have ever replaced batteries from UPS and see the batteries swollen you will know what I am getting at ).

12 Volt example drained to 11 volts.
A charger built like this will when first placed on a "dead" battery will show a voltage close to the battery voltage and the maximum current allowed. As the voltage increases the current will decrease. When 14.2 volts is reached the charger will drop to the float voltage to prevent over charging.

In my experience this will get the most life from this type of battery.

For the past four years my lawn mower and trimmer have ran off of SLAs. This is pretty hard on the batteries but they will still last around two years. By the way, where I live the grass grows year round if I water it

I do use a "boost type" voltage regulator that use PWM to convert the nominal 12 volt from my main battery bank to the 14.2 volts.