Wednesday, September 4, 2013

Lithium Upgrade

This spring, during the Fort Collins City Council election, I upgraded the Toad Car (the VoltWagen's actual name) to lithium.  This was done so that the Toad Car could ride in the 2013 St. Patrick's Day Parade downtown.

I used some CALB 40Ah cells I had from a project that never got off the ground.  This involved significant changes to the electronics - mostly to support a battery management system.  Here is a picture of the upgraded electronics in the rear (under-seat) compartment.  The black box at the top is the charger.  The blue circuit board left of center is the BMS controller.  And the aluminum box right of center is the motor controller:

Here is a (poor) shot of the front compartment electronics.  There are the most positive (red) and most negative (black) terminals in the center; the key switch on the right; and the EV display sender board toward the left.  Also shown, in the lower right, is a 24V->12V DC-DC converter, and eight of the lithium cells:

Finally, in the very back are the remaining 8 cells.  The cells are arranged in a 2P/4S configuration.  This means the original 40Ah cells are grouped together to make 80Ah groups, and then put in series to make a 25.6V battery.  On each parallel group is a BMS board - you can kind of see them here, with green LEDs lit:

Here is a picture of the complete wiring diagram:
You can download the PDF from this link.  After much thought, design, experimenting, and testing with a voltmeter (notice it in the first two pictures :-), I got the wheels spinning on March 13 (the parade was on March 16):

I also upgraded the rear wheels to 14mm axles, and added disc brakes.  Finally, here is the car in the parade:

Not shown in this picture is one of my best friends, Jeff, who helped keep the car running - it kept throwing a chain.  Jeff is the tall bearded man at the left of this picture:

And, of course, my wife Jill (pictured with the camera bag) supports me and puts up with my crazy experiments.  Thanks, all!

1 comment:

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