What we really need is a tiny UPS, of sorts. We'll be hooking up a solar cell and a battery to a single board computer. Currently, that SBC is a custom Pic32 device, and it does it's own UPS and voltage monitoring duties.

I've been tasked with trying to replicate all of its features with off the shelf products... and for the most part I've succeeded. But I don't currently have any way to switch between two sources of juice, or monitor when they're getting low.

These guys have something:

http://www.mini-box.com/picoUPS-100-12V-DC-micro-UPS-system-battery-backup-system

I really like it, the price is well within the budget. We might even work it in though it does 12V and I'll probably be using 5V... there are enough engineers on hand to figure out something. But I'd still have no idea what the voltage was for the PV or battery. I was hoping that there was some simple little USB multimeter thing that I could use to monitor this with, but I can't seem to come up with anything. I've found all sorts of cool hardware, but nothing that will help us.

Does anyone know of anything?