Pete's Log: Solar library: getting ready for winter
Entry #2032, (Home Automation)(posted when I was 43 years old.)
The new battery for the solar library finally gave out after roughly 110 hours. At a nominal 6600 mAh capacity, that works out to about a 60 milliamp draw, although I suspect it was probably slightly higher as I doubt I got use of the full 6600 mAh. When I first embarked on this project, I measured a 80 mA current draw when connected to WiFi but with the lights off, so this feels like the right ballpark.
Then I plugged it into USB power (since it's been grey and I had it indoors) and it took roughly 14 hours to charge back up. I'm still using the old solar charging circuitry and it's configured to max out at 0.5 Amps by default, so 14 hours sounds roughly correct. There is an option to solder a jumper to make the charging circuit deliver 1 Amp, but since I was using a 6V/3.5W solar panel, there wasn't much chance of seeing a lot more than 0.5 Amps anyway.
My new solar panel is 6V/6W, so should be able to deliver 1 Amp in optimal conditions. And the new charging circuit defaults to 1 Amp, although that is configurable too. The new battery supports a maximum charging current of 1.5 Amps, although they recommend going with 1 Amp. So overall I think this will be promising. In optimal conditions the panel and charger should be able to fully charge the battery in about 7 hours. And the battery should be able to tide the library over several grey days. Have I mentioned it's been real grey lately?
I've been having lots of ideas about measuring the actual charging current or monitoring both the battery and panel voltage at the same time. And building circuitry to stop power being delivered to the ESP8266 when the battery is below a certain level. And those all sound fun, but time-consuming.
So the goal is tomorrow to just reassemble everything and get it reinstalled in the library. And monitor how these tweaks serve me. And not get bogged down in ideas I don't have time for. At least not yet.