The is "trickle charging" kit available in market....
Actually it is not trickle charger. It is wrongly said so. What it does is it limits the maximum current of charge. It acts like automatic dimmer. Triac is in series with transformer's primary. When current in battery lead is detected above a certain level set by pot, it dims and vice versa. It is effective in regulating the charge.
When charging current is measured of ups, a dischageed battery at 9V is charged at 30A and when it reaches 13V, it is now only 5A. So it helps protecting battery, protecting rectifier diodes and do rapid charging.
It is only a add on kit, the original battery full cut off circuit remains intact. When battery is full, charging is cut off (which is also called float charge). Battery full cut off point depends on battery type, its temperature and other factors.
In trickle charging when battery is charged at high current and reached to fully charged point instead of cutting charging instantly charging voltage is lowerd. For example if full charge is set to 14.4 volts on battery now charging voltage is set to 13.6 volts. Remember initially current is maintained and then voltage. Trickle charging is used because last 10 to 15 percent on charging can be done only thrugh this process. It is slow charging. In our situation when every 2 to 4 hours when elctricity is cut off it is useless. There is less possibility that your battey is charged through rapid charging in this time.
If you see indian ups kits this triac (better using two SCRs) phase control circuit is buit in and also controled by the micocontroller.They were using it many yeas ago. Trickle charging, you will see in switching mode chargers buit in like small chinese ups.
When battery is not in use and not properly charged, a white powder is observed on plates. It is lead sulphate.It won't let the plates to pass the current. Somtimes battery becomes useless. Pulse charging is a way to remove it by applying very high voltage pulses of very small duration for weeks. Somtimes battery is revived.