Currently working on a project where we have a requirement to power circuits using battery (12v 7.2Ah SLA) ,

When the the circuits are connected to a power source been 15v 1.5A DC-DC Converter and to automatically float charge the battery.

Any ideas as we have been experimenting using the LM317 with little success

 

hi Stream,
Welcome to AAC.
The LM317 is unsuitable for a 15Vin to 13.8Vout charger as it requires a Vin to Vout of at least 2V.
Search your local components supplier for Very Low Drop out regulators
A type that has a Vdrop out of < = 1 V should work OK.
E

 

If you want a 3-stage charging circuit with a constant-current initial charge, constant-voltage top-off charge, and constant-voltage trickle charge, the circuit below should work for you, described here.
Substitute the LT/LM1117 for the LM317 for low-dropout operation.

 

Thanks crutschow as that's perfect !!

Wondering if there is a PCB already for this ? If not any recommendations ?

 

Wondering if there is a PCB already for this ? If not any recommendations ?

Sorry, I don't know of any.
You can build it on a perf board.