I'm wanting to experiment around with battery charging and am looking for a controller that is easy to use and has more capability than Basic Stamps. The preliminary plan is to use A/D to read battery voltage and current and use PWM to a SMPS circuit (buck, sepic, flyback?). I want to scale the analog inputs to voltage and current, and display to a PC or character LCD display. I know so far it sounds like I'm re-inventing the wheel but I'm wanting to do more, such as a log for each battery pack and its capacity over time, how many times charged, last time it was tested by cycling, cell balance, etc.
It looks like the Arduino is economical, easy to program, and capable enough for what I'm wanting to do. I haven't bought an Arduino yet, I'm considering the Mega 2560, are there other similar microcontroller boards that I should consider?
The Arduinos are easy to get up and running. The "can't get it working out of the box so it ends up unused on the back of a shelf" factor is very low. There are lots of "shields" available to provide additional capability without needing to resort to DIY board layout or stripboard/protoboard.
There are also tons of other dev boards but the typical one doesn't come with a free development environment, expansion boards, or support community.
They usually do come with a free development environment:
$10 for three li'l modules, doesn't get much cheaper than that:
Several support communities, including one on Yahoo that is accessible via gmane in newsreader-compatible format, just like this newsgroup. The development environments are typically code-size restricted but the limit is usually larger than what can be crammed into a smaller uC and should be plenty sufficient for this sort of job.
It is possible to have the uC also do the PWM regulation but that is something I would never recommend to a beginner.
\ \If you want to charge many kinds of chemistries, just buy a Imax B6 \charger on eBay for 10$ and you're done. \
For what I would like to do I would need 4 or 5 Imax B6 chargers networked together and controlled by one central controller, or possibly 1 charger multiplexed to multiple battery packs. I'm wanting multiple ports and different configurations. My primary use is Radio controlled flight. At the flying field I would have maybe 6 battery packs, one in the model, one cooling after use and before charge, and 4 charging, allowing 3 or 4 flights per hour after the 6 battery packs were used. This would be a field use mode.
\If you want to design a charger, do it around one of the many all-in- \one chips like the MCP73837.
I'll look at those, most battery charger chips I have seen want to handle the charge process automatically, that's fine for an ordinary battery charger but I'm wanting to be able to control the process.
\Why you would want to get down to sampling ADCs and then try to re- \invent the year's worth of engineering required to do a good job is \baffling, to say the least. \ \It's all already done. The B6 can be connected to a PC and you can do \logging. How you keep track of each pack is something you'll have to \work out yourself.
I'm wanting to be able to connect multiple batteries to a charger and control them all at once, not just for charging but also for storage and maintenance. LiPo's are supposed to do better being stored with around 3.8V per cell but charged to 4.2V per cell for full charge. Also I would like for one of these chargers to be connected to my 12V lead acid batteries that don't get used much in the winter, riding mower, trolling motor, tractors, forklift, and vehicles that I don't use often in the winter. This would be a float charger that would work something like a battery tender but able to handle multiple 12V batteries, or even mix and match of batteries (3 ports float charging lead acid batteries while another port is fast charging a lithium Ion pack.
The charge algorithms don't seem all that difficult, limit current, limit voltage terminate at a voltage or peak detect, depending on battery chemistry. I also want this charger to be able to test battery packs, check their capacity and internal resistance at different times in the life of the battery. I could do this all manually using the USB recording of my chargers but I would prefer to automate the process than spending years manually maintaining batteries.
This kind of stuff isn't worth it for most people but some of the larger R/C models take $300-$400 battery packs, buy 4 to 6 battery packs in that price range and proper care can become pretty important.