Very cool, I have been trying something similar with a boost converter...
It's been awhile since your last post, how's your boost converter going?
I've built the boost converter with mppt to charge ebike battery using solar panel, but most (pretty much all) arduino uno processing power goes to the custom pwm, as I need pwm freq faster than 50kHz. I should research to uno pwm capability better shouldn't I?
Anyhoo, trying to fly my flag here, my boost mppt charger, works well and tested, here:http://epxhilon.blogspot.com.au/2014/04/bmppt-solar-charger-2.html