Hi Folks,
I am very new to the world of PIC's, and would like some advice on which direction to head in a project I'd like to implement using PIC's. Some backround on myself first and then the design. This is long so get comfortable...:-)
I have a basic grasp of electronics (just passed ISCET certification, studying for FCC) and have been interested in using PIC's for a long time. I bought a bunch of books and have a programmer and demo boards, but never got past blinking an led.
Just recently, I finally convinced work in footing the bill for the PIC class offered by RCG Research. It was a great class for someone like me. Someone who has never really done anything with PIC's, but understands the general usefulness of them. It also helped that I had some electronics training.
Anyway, after having gone through the class, I feel that I can now jump in with both feet and begin experimenting. Which brings me to where I think I need help in deciding which way to go, as I have an idea where the PIC and all it's power can help me out.
Here is what I have currently: I have a battery that is comprised of 15 cells connected together. It is charged via a constant current battery charger that feeds 4 amps (voltage varies) to the battery until I decide if all of the cells reach 2.05 volts. Each cell has to be checked individually as they NEVER come up to full charge at the same time and it is critical that they do not exceed the 2.05 volts for any length of time, as it tends to short the cell.
Since cells do not come up to 2.05 volts evenly, AND the battery as a whole is being fed 4 amps, when a cell does come up to charge, it is "shorted" with a resistive wire, while the other cells continue to charge. That "short" cannot stay on for too long, as the cell will now slowly lose it's charge. As you can see it becomes a rather tedious task of shorting, and unshorting each cell until they all come to their full charge. Lot's of fun let me tell you.
What I would like to do it feed the charge current to a bus that can supply each cell individually through a relay, MOSFET, or some high current capable "switch" that can be controlled via a PIC or series of PIC's. Obviously the PIC would need to read each cells voltage, then make a decision as to either open the "switch" or leave it on based on that cells indivdual voltage reading. I would also like to display a cells voltage if selected (through a button press or maybe a rotory switch?). As well, during a "discharge" cycle, the PIC should be able to turn that switch on or off depending on the cell's voltage.
I know it is possible to do this with PIC(s), but what kind of approach should I take? Do I use a high pin-count PIC that can do it all, or do I use multiple PIC's talking to a "Master" PIC? I don't want to take a super long time developing this, cells are VERY expensive and this would greatly extend their useful life. I can buy a really fancy battery management system for about $80,000 US, but I would like to do this as inexpensively as possible.
There are a lot of really smart people here and I would like your educated opinion in which way to lean as far as using lot's of low pin-count PIC's or a few/one high pin-count PIC. By all means, if you have questions ask away!
Any advice would be greatly appreciated.
Thanks in advance.....
James
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