Regular battery charges even the low 2 amp ones will boil the acid in small batteries and the gas produced will bleed off and it will go low on acid after awhile. The lead plates can also warp if left charging for a long enough period of time.I never leave a charger like a 2 amp on a small battery more than 24 hrs. even then thats risking an overcharge,
you might think you're not doing the battery any harm but its so easy to overcharge these small batteries.Its like trying to pour a full 5 gallon Gerry can into a 1 gallon container.
The low amp trickle chargers work for charging the smaller batteries but again they arn't designed to be left on the battery for an extended period of time,using one of these you should check the state of charge til it gets to the 13.8v approx, and then unplug it, the battery will drop back to approx, 12.4v or so,thats normal.
The Battery maintainer is designed to first charge the battery up to
13.8v which is called a surface charge, then go into a Float charge mode which deep charges the cells for a length of time at 13.8v then go into the maintenance charge which is actually when it shuts itself off and may sit dormant for a few days until it senses the voltage has dropped below a preset level approx. 12.8v it will turn on and charge again unil it reaches the maintenance 13.8v again and then shuts off.This cycling prevents acid gas,overcharging,and warped cells.
This may not be a very scientific explanation but hopefully one which is easy to understand.
The actual voltages quoted are only approximate but within the limits generally excepted in electrical sysyems using 12v
I agree with Whacker, he's right ,I just expalined it a bit differently.
-Robert-