I'm having a bit of a clear-out, so rather than scrap my half-finished projects I'm going to offer them to anyone who wants to experiment, deconstruct or improve them. These are all prototypes I built, with full documentation:
1. A car alternator, rewired with my own design of voltage regulator module which allows for adjusting the output voltage, low-power standby operation and running at lower than designed RPM. Ideal for use in something like a very-small-scale hydroelectric project.
2. A MPPT DC-DC converter. Attach to a 100W panel for instant MPPT operation. Sort-of works on charging batteries, works very well on resistive loads. Good for heating water. Much room for refinement.
3. A PWM solar charge controller. Open design and firmware. Good for 12V panels, up to 200W. Designed for lead-acid batteries - sealed, flooded, AGM, just set the voltages. With some software work it could also manage nicads or NiMH.