Help getting design started....

[rossfree]

Hi James,

Curious... this multi-cell battery arrangement... are all of these cells in series? If so, can you add wires in-between each of the cells... and pulse charge them individually depending on their current voltage reading?

I'm no genious... but it seems if you had access to each cell, you could first read it's voltage, then smack it with a charge pulse and then move to the next cell. If the cell was fully charged, you'd skip over it. You could store each of the cells voltage for recall and viewing at any time on a display. You would not need to short the cell with a resistive charge. This assumes you have the multi-cell battery off-line for charging... such as a cordless drill battery.

The pic is a good choice. If you are new to PICS might I suggest that you get playing with some code a bit... scrounge the internet for some circuits that might be related to what you are doing and start playing with it.

I assume you have PicBasic Pro.

I purchased Microcode Studio Plus with it's Bootloader. The 16f877 is a nice fat chip with plenty of breathing room and peripherals. It's more than you might need but inexpensive enough and you can stick the bootloader in it. I can't say enough how much the bootloader has helped me along. It's great for a beginner. You write a bit of code, press a button (to load your program into the chip) and see what you've done... instant feedback!

I would love to hear more about your project.

Good Luck,

Ross

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[sincity337]

Ross,

Thanks for the info. I think you are suggesting some of the same things that I was leaning towards. I have been doing lots of searching on the net and found some "universal" chemistry battery charger chips from Maxim, can't think of the model number off the top of my head right now. Apparently it will do what I want, I just have to set up the voltage and current reference and it applies and releases the load as needed. I guess I could use the PIC as a "supervisor" if you will, to enable each cells charger and even read and display it's voltage reading.
I am currently waiting for my supply guys to order the evaluation kits for the Maxim IC's. If I get them to work, and work with a PIC I will definitely let you know how it goes.
Thank you so much for the input. It is really important for us novices to get input and helpful hints from people that have more experience.

james

[sincity337]

Just for the curious:

I have requested information from Vicor for their power supplies that may work for my battery cells. I need 2v @ 4A constant current to charge the cells, and they have a system called the MegaPAC that holds their power supplies mounted as cards. Each card is controllable via a logic gate to turn it off and on. I think I might be able to easily (HA!) program a PIC to monitor voltages for each cell and switch the power supplies off when the cell voltage reaches 2.0v.
Of course I really need to sit down and decide what other features or controls I would like to include in my program.
Anyway, thought you guys would at least like an update on what I was doing with this project.

James

[Acetronics2]

Hi, Sincity

There's a simple solution, not needing PIC's !!!

Have a trip to Modeller's forums ( www.rcgroups.com i.e. ) and search for LiPo Balancers ...


THE link : http://www.rcgroups.com/forums/showthread.php?t=270580

Dan Baldwin's scheme is, I think, the most efficient here ...


The goal is not to have a cell voltage over 4.2 volts ...

I think it sounds something good for you !!!

Alain