So, this weekend I did plan to run from solar full time to see how it’d go.
Mother nature did not co-operate. I think there was about 2 hours of sunlight! This is what the 24 hour rain map looks like from the local weather radar (image credit: Bureau of Meteorology):
In the end, I opted to crimp SB50 connectors onto the old Redarc BCDC1225 and hook it up between the battery harness and the 40A power supply. It’s happily keeping the batteries sitting at about 13.2V, which is fine. The cluster ran for months off this very same power supply without issue: it’s when I introduced the solar panels that the problems started. With a separate controller doing the solar that has over-discharge protection to boot, we should be fine.
I also have mostly built-up some monitoring boards based on the TI INA219Bs hooked up to NXP LPC810s. I have not powered these up yet, plan is to try them out with a 1ohm resistor as the stand-in for the shunt and a 3V rail… develop the firmware for reporting voltage/current… then try 9V and check nothing smokes.
If all is well, then I’ll package them up and move them to the cluster. Not sure of protocols just yet. Modbus/RTU is tempting and is a protocol I’m familiar with at work and would work well for this application, given I just need to represent voltage and current… both of which can be scaled to fit 16-bit registers easy (voltage in mV, current in mA would be fine).
I just need some connectors to interface the boards to the outside world and testing will begin. I’ve ordered these and they’ll probably turn up some time this week.