In theory it can,
But, many chargers charge the battery with 14.2 ~ 14.4V, and when they detect that the battery is nearly charged, (the charge current drops to lets say 200mA), they lower their voltage to 13.8V.
The 13.8V is the ideal float charge voltage for many lead based batteries.
the 14.2V is to much, if you charge your battery for too long with this voltage, they will dry out. And will be damaged.
If you add load to your system, your charger will see always a current greater than 200mA (or whatever your charger trip point is). and always will supply 14.4V.
This can be fixed, to add a diode in series. the diode will drop around 0.7V so your battery will never be overcharged.
But it takes significantly longer to charge.
secondly you need some sort of low voltage cut-off.
depending on how long you want your battery to last, somewhere between 10.8V an 11.8V.
(the higher the cut-off voltage the longer you battery will last, but the less run-time you have) (also you can use around 40~60% of your rated battery Ah if you want to use your battery more than once).