Last night, I soldered up the first section of the BMS board. On the top side of the PCB there’s a processor, an FTDI USB bridge chip, a bunch of fuses and a handful of passive components:
On the bottom of the board, I soldered on four (out of the 50) shunt resistors:
I am mounting the shunt resistors away from the board to allow for better air flow. They get pretty warm with 2.5amps flowing through them.
So far, the initial tests look good. I am able to program the processor, flash LEDs and send data over USB. Next, I need to test communications to the LTC6802. In order to do this, I need to wire it up to some batteries. I’ve got some nice connectors on order to make this job easier and more fool-proof. They should be here in a few days.
I also spent a little time welding up some brackets to hold the roll cage in place. I’ll snap some pics of these next time I am down in the shop.
Here it is:
Not bad for $100. I had http://goldphoenixpcb.biz/ fab it. I’ll start soldering it together soon.
Tonight, I spent some time writing code to decode the serial output of the multimeter. The serial stream represents a map of the 7-segment LCD elements on the display instead of just a simple reading. So, it took a little work to map out the characters. However, it now works and can now start work on my fuel gauge code. This code will eventually go onto the “creature comforts” circuit board that I am designing. This board will:
- Act as a fuel gauge
- Be an interface to the heating/air
- It will monitor door sensors (and will drive the dash lights)
- In will produce a “bing” if turn the ignition off and leave the lights on or leave the keys in the ignition and open a door.
Additionally, I bought a handful of parts this week:
- LED backup lights from ebay. This is sort of a test. If they work, I will buy similar lights for turn signals, brake lights, and markers.
- 500amp 50mV shunt (my 1000amp 100mv shunt isn’t giving me good readings)
- Meter to read the current shunt (I got the $60 radio shack special and it works great)
- Fiero windshield wiper motor and controller board
Last but not least, I cut out a small bracket for mounting the fire extinguisher:
