Solar / Lead acid battery / Load management

[brendan-petrol]

Hello guys!

I have a question: one of the projects I'm working on has come to the attention of my boss! Basically I'm making a rainwater tank level sensor with an MPX2010 sensor. He would like one at his tank, which is about 100 meters way from his house.

The wireless part I am OK with, however the power is my issue. He doesn't have power at his tank (it's a gravity feed system on a hill), so I want to put in solar.

Does anyone have any resources or advice on how I can use solar in my project? I was going to make a PCB for use in future projects (because I always like to make re-usable components!), so what I would like to do is make a circuit which can take solar power in, charge a Lead Acid battery (with a proper multi-stage charger) and output 5v/3.3v.

Firstly, what sort of charge IC can I use with solar (at a good price)? How do I hook it up to the load such that it doesn't interfere with the multi-stage charge levels? If i just put the battery and load in parallel would the charger still detect the right charge levels?

What is the best way of measuring the battery level? Just a voltage divider and the ADC in an AVR?

Lastly, what's the most efficient way of making the output voltages? I would use a switchmode IC, but is the level they output not dependant on the input voltage? If so, would the charging/discharging voltages be too different and cause issues? Or is the output voltage change not significant in this sort of scenario?

Thanks,
Brendan