12v sealed lead acid battery charger

Looking to build my own custom battery charger/ trickle charger for my motorcycles.

Brief: I have 4 motorcycles That are ridden anywhere from daily/weekly to maybe only once a month or less. With time the security systems and always on accessories slowly drain the batteries.

I could buy a trickle charger for each bike but that would be quite costly alternatively I could put together a few readily available components to build my own smart charger. Idea being each bike has a little pig tails hidden somewhere easily accessible and when I park the bikes up I just plug them in walk away and for get about them until I ride them next.

This is what I am thinking:
240v ac - 12v dc PSU q. how many amps?
An Arduino to control the charging
A few 7 segment displays or maybe a single LCD display to indicate status (have both in my parts box)
Some voltage reading modules (have some in my parts box)
Relays (plenty in parts box)
Wire, terminals etc

I haven’t done much research but I am guessing it’s as simple as taking a reading from each battery, and cycling power from the PSU to each battery. Rinse and repeat and as hard as a bunch of technical data about charging/maintaining batteries.

Obviously I need to isolate the Arduino using the relays and voltage reading modules.

My skill level is intermediate, I can handle the code and the wiring, looking for help with the technical side of trickle charging and maintaining motorcycle batterie.

If you just want to trickle charge each battery to prevent it discharging you won't need any fancy electronics. Just get a DC power supply that can provide the right voltage and you can leave it connected forever. The Battery University website will have details of the appropriate voltage.

...R