Solar Charge Controller with Simple LM317

Researching another solar SLA Charge Controller. Update: I have abandoned this LM317 project

The resistor between Vout and Adj pins seems larger (1k) than on most of the reference/app note schematics that I've seen (~120 to 240 ohm)

Hi westfw, I tinkered with this circuit in a simulator and got myself convinced it was worth trying, but now that the board is shipping from OSHpark probably will not even order the parts. I fear the simple battery disconnect method used here will just flip the load on and off in the morning because it lacks startup sequence logic, also the LM317 has a huge dropout voltage. I should change this board to use the LT3652 for a 12V SLA setup, having found that chip works, but need to ditch the latching Relay in my CC01 board. This board got me looking into using a P-Ch FET for the battery disconnect and now have a simulation working that shows a power up Sequence idea*, so will try that first on the CC01 board.

  • runs in Chrome With this new setup, I am hoping for a clean power up once the solar has charged the battery to 6.5V, but expect some debugging will be needed. What is going on now (on CC01) is bounce from the relay during battery attach, and a poor power up as the sunlight increases in the morning, which has got me worried about CMOS latch-up.