Ok this is where I started...
Schottky drops is not a problem here as all the stuff works down to about 10V fine.
Problem is I can easily substitute an LM317 or whatever charger in there but it has three drawbacks which I want to solve:
1. No over-discharge protection of the battery.
2. No intelligent cycle charge if the battery is suddenly discharged due to an outage.
3. No over-current protection. They can deliver 100A or so. Woosh.
This lead to this drawing which covers the above and over-voltage protection if the LT1083 fails. The main problem is what sits in the magic box
If it handles the LT1083 regulator role and the diode OR gate function as well then I'm happy.
I can design something which will do this with a UC3906 and MOSFET switch etc but I'd rather like to just buy something because I can't be arsed