The evapotron has a series of challenges. First, I can’t let the charger run while the battery is under load. That will fry the charger pretty quickly. OTOH, lead-acid batteries die when they overstressed or overcharged.  This all means  means that either I have to constantly check the battery load, or I have to automate it. Also the pump doesn’t seem to know when to quit, in two ways. A) it keeps pumping when there’s nothing more to move; and B) in practical terms, it doesn’t really need to run constantly. It could run every 10 or 15 mins, max.

So if I’m gong to control charging and timing, an Arduino is going to be involved. At that point, I kind of went nuts. Why not keep track of the battery voltage? The pump current? The water level in the reservoir? The water temp? The flow into the reservoir (i.e., total input)? And once all that’s happening, why not log it all to an SD card? And it’s going to need a minimal UI to watch it all. And the next thing I know, I had this.

The part on the left is pretty stable. There will be a bunch of wires from the sensors in the reservoir and the pump brought together in a junction box with a 4′ cable to the control box where the Arduino, battery, and charger will live. I’ve just started thinking through how the junction box will work.

The junction box has to be mostly weatherproof (it will be somewhat sheltered under the evapotron) but the control box needs to be sealed. Dust, rain, spilled grey water, etc., need to be kept out. Good thing I bought some Sugru.