So here's a relatively simple project I've been toying with for the last few days. Originally started out as just a series connection of LM317's as current and voltage limit, but it's relatively difficult (read expensive when you're building a few) to find low power adapters in the 20V range.
So I thought I'd use some of the 5V 1A USB chargers that are starting to become all too common as smart phones proliferate.
So this all works well on the bench. I've attached the schematic and output IV curve of the circuit. The 15-20Ah bike batteries I've tested all sit around the 30-50mA on float once fully charged.
All the input protection has been thoroughly abused and everything appears to be holding up fine.
Note that while the components on the schematic are what I used for a through hole prototype, the end result will be SMD so exact part choices still need to be made.
So feel free to point out anything I've missed before I send the board off to manufacture
Cheers
Edit: attached schematic with current sense on the correct side...