Hi.
Sorry for bringing up this old post.
I am designing an intruder alarm system. System needs a backup battery. Battery type is 12V sealed lead acid battery. Battery capacity is limited to 7Ah and typically it is a 4.5Ah one or 7Ah. It is recommended to limit charging current up to 10% of capacity. So I decide to use 450mA as current limit.
I tested some battery charger that are using lm317 and I am not satisfied with their performance.
I test your circuit. It is working good enough. But I wonder it could be more minimal?
For now I don't care about temperature compensation so I removed D2 and D3 and R6. Also I removed other elements such as R5, D2, C2 and overall performance is almost the same.
I have some questions about it.
1- Did you actually make your circuit? And what was the long period performance?
2- What would I miss by removing D4?
3- What would I miss by removing R5?
4- What are the advantages of adding capacitors in lm317 output like C2?
Final circuit is this: