Thursday, July 1, 2010

Talking to Batteries

EVT has worked a lot with the A123 26650 cells: we've cycled them, rapid-charged them, drilled into them, built packs out of them, all in a few semesters. At the beginning of this summer, we even charged the whole eMoto pack in 11 minutes and 30 seconds! This spring we got a shiny NEW toy: an A123 Prismatic Module.

The A123 prismatics have a much higher energy density than the 26650's and they come in a sweet pack arrangement. We have some single cells that we've been testing, and Lennon and Shane have built a rig to cycle one prismatic 1,500 times at a 6C charge/discharge rate. More updates on that later.
For the past few weeks I've been working on using an Arduino and an MCP2515 chip to talk to the BMS built into the Prismatic Pack. It talks over a CAN network, much like the systems in the Porsche or the elEVen. I've found that using the Arduino allowed me to start communicating in CAN easily in only a day or two, and now I can intelligently talk to the module, polling it for voltage and SOC information and telling it to actively balance itself. In the picture you can see the Arduino board sitting on top of the module, and the cable running over the top that connects the two together. The next step will be to output the battery data to a screen and create a system for talking to multiple packs, like we'll have on the next EVT motorcycle.

Say hello to the newest member of the EVT fleet, a blue Lifan motorcycle. This is the same frame that eMoto was originally converted from, and soon it will hold the above prismatic module and a shiny new motor. Last week Lennon, Randal, and I traveled down to Providence and bought the 2-year-old gas motorcycle from a guy who had never ridden it. When we returned, Randal and I ripped the combustion components and twelve volt system out (the lights and fairings had already been removed) and Will has begun designing a new frame to mount all the electric components. Look out for updates on the new frame and another new addition to our team.


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