Arduino BMS

As I can't afford a Batrium, like others I was thinking about an Arduino controlled one and want to run my design my for feedback. I'm pretty good at coding but weaker on the electrical side so any feedback welcome.

Using a Arduino Wifi my logic would be:
- scan voltage of each cell, judging off a moving average of last few readings - guesstimate of voltage (remove variance in readings).
- Any cell to too high or too low disconnect battery (low/high indicator leds)
- Any cell that is fully charged (high but not too high) and other cells that are not (by a set percentage) turn on a fan powered by that cellvia a relay to cool the pack and draw the cell down to balance the load ( I can change the load to different draws).
- Check temperature readings and if high (not sure how high?) disconnect the battery
- send voltage and temperature readings to my website or thingspeak to graph/view it.
- maybe check and report current too

Rough design:
https://www.dropbox.com/s/0zdbwd41f1tcpqi/Arduino BMS.png?dl=0


Most of this I think I can do but any suggestions on a switch/relay that can handle high currents?

Any other suggestions / things I have got wrong?

Stuart Pittaway's diyBMS. He's done all the hard work

https://www.youtube.com/user/spit2k1

At least you could use his design and improve upon it. He has it as open source.

Adam Welch and Julian Illet have done videos on it as well. And there are several members here who are using it.