Now that we have a 20 amp-hour 12 volt battery, charged by a solar array delivering up to 125 watt-hours daily. To put that power to use, we'll need an inverter to convert battery power into household 120 volt AC power. This way the collected solar power can be used for more than just charging USB devices.

An old inverter was dug out of the old equipment collection, but it could only sustain about a minute of work before it would stop, reset, and restart. This isn't great for the electronics, but what made it intolerable to humans were the cascade of noises that devices emit when charging began. Hearing the symphony roughly once a minute was unacceptable so the search begins for a replacement AC inverter.

The Harbor Freight lineup of AC inverters were obvious candidates. Starting from a basic model just under $20 and going up from there. While investigating options outside of Harbor Freight, one stood out: Monoprice #15278  "PowerCache 220"

It is designed exactly for the task we're building for. It can accept power from a solar array to charge its 18 amp-hour 12 volt battery. That power can be consumed directly as 12 volts DC, as 5 volt USB power, or as 120 volt AC power.

The PowerCache mostly duplicates the components already in the current solar experiment setup. Buying one might be called wasteful, but for the sake of exploration we'll call it redundancy. This nearly doubles the battery capacity and allows more ways to put solar power to use. It is also more user-friendly than the current maze of wires and connectors. It is an enclosed unit therefore easily portable. This might come in handy if we ever have a reason to take a little portable power source on the go.

So the search that began as a search for a simple AC inverter ended up with purchase of an integrated unit that included the AC inverter and basically everything else short of the solar panels themselves.

PowerCache 220