Hi,
I've recently been asked to help out in an artwork installation using solar powered LEDs.
We want to have a set of self enclosed (no interwiring) units consisting of a battery, solar cell or array and a single 350ma (1W) LED to operate for 6-8 hours at full brightness per night and a contingency for 2-3 nights capacity on rainy days.
I'm capable of specifying the battery size, cell size and MPPT controller working out the maH needed. However I'd like to design a MPPT to reduce cost as off the shelf solutions meeting the specs are a little too capable and expensive.
Maintenance and battery replacement are to be as low as possible....I'm looking at SLA or gel batteries. If anyone has other advice....please advise.
From what I gather a MPPT will track the PV voltage and current and the battery voltage and current, then using a switch mode DC-DC converter adjust the battery charge voltage to maximise the charge current. In essence its a variable DC-DC converter. As we need to roll in a fixed ON time, I'm expecting to use a small micro with a fast PWM to the DC-DC converter.
Can anyone provide a link or advice on designing MPPT controllers. Perhaps a reference design or theory link? Any specifically designed chips for this application?
Thanks
Phil