I like the idea of a timer, but consider getting the wall wart voltage under control. I measured some around, one labeled 12v measured 17.8, a 10v measured 14.9. The battery will drag voltage down, *but* will be in overcharge once the first couple hours are completed. Overcharge damages a battery as well as undercharge, so it is avoided in commercial designs. With a wide variance in wall warts, do we have enough information to determine 1hr/day is acceptable?
Improvement Idea:
1) Find a timer that will run less frequently and for a lower duration. Something like a sprinkeler timer could get to 1/week or ever 1 every 2 weeks for a couple minutes.
2) Test your wall warts with a meter, and select one with a voltage around 14-14.4v. Most wall warts are not regulated at all. This is going to mean ac line voltage will be a factor. Finding 'xyz' network wart is close will be way off if someone else's AC line voltage is 10% different than yours.
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Now a look at what it takes to add regulation:
I'm came up with an example low cost voltage regulator. Nothing special, a regulator chip, in a regulator circuit! A preliminary parts cost is around $3.00, without the wall wart cost. From this base its easy to add a float setting too, and eliminate the external 'lamp timer'. If anyone wants to actually build one, I'm happy to post the circuit in its final form.
I worked for a time performing failure analysis of lead acid batteries, charge system and in-battery pcb failures. There was no shortcut to good life. Charger needs to operate within manufacture's charging guidelines, charge times followed and prompt recharge is important.
If interested enough to think of maintenance charging, my opinion is to start out with a charger set for the proper voltage. If you look at commercial battery maintainers, this is not an original opinion
