Thanks for the reply. In fact I’ve already tested a simple solution that works. I do have v1.3 and have studied the diagram you suggested. What I have done, and found works, is to simply cut the lead on pin1 of the LM2596 (the one that provides the input voltage). To get power to the RPi and Ray’s board, I simply wire a “cigarette lighter” to the battery and use a usb charger connected to the micro-usb port on the RPi. This turns on the RPi and the green LED on Ray’s board shines. So far, it works great! I use the PowerStream 12vdc -> 24vac, wired in parellel with the usb device. I connect the output of the PowerStream to the orange connector on the OSPi. I’ve also wired the power to the PowerStream with a 30amp relay that I bought at an auto store. I’m planning to control that relay with the one on the OSPi circuit (haven’t tried that yet, but I don’t expect a problem; the PowerStream could draw 5.1amps and I don’t want to stress the relay on the OSPi). That way, I can turn on the 24vac only when needed (when the sprinklers are running), so as not to drain the battery too much. I’ve ordered a 100W solar panel (get it next Tuesday), and hope to “field test” (literally) next week.
BTW, I also installed a 7.5 amp fuse on the plus side of the battery, just in case.