LCA2010 Presentation Proposal

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Contents Wellington January 2010


Recent advances in lithium battery technology make converting a regular car to a practical electric car easy. More difficult is preventing your expensive lithium battery dying an early death, or worse, catching fire. The Tumanako BMS (Battery Management System) is an open source hardware project that provides full management of each cell in the battery and contains redundant layers of hardware and software safety systems. Open source design with an open source tool chain allows us to fill an important gap in the EV component market without giving users a black box and no idea how their battery is being looked after.

Each cell in the battery has a dedicated monitoring circuit with a small Microchip PIC CPU. Communication among more than 100 cells in a 350 volt battery is accomplished by transmitting CAN bus packets across an isolated RS485 bus. A master unit bridges the BMS's RS485 bus and the CAN bus in the rest of the vehicle, protecting the battery from the battery charger and motor controller. The hardware schematics, PCB design & firmware are open source and available on Sourceforge at

The talk will address:

  • Electric car basics
  • Differences between battery chemistries
  • Battery management theory
  • A brief overview of other BMS systems and why I chose to build my own
  • Embedded development from the point of view of a Java developer
  • CAN bus intricacies
  • Lessons learnt designing the hardware

My electric Mini will be available for viewing at the conference.

Non-standard technical requirements

Bringing an electric Mini into the room would be a great party trick, but isn't necessary. Somewhere to show it at (an)other time(s) would be really good.


  • Trailer from hirequip $510+gst + 1000 bond
    • Pick up Sat 16 Jan Auckland
    • Drop off Newtown Wellington Mon 18
    • Pick up Sat 23 Newtown
    • Drop off Friday 29 Auckland
  • Falcon tow car $79/day usave car and truck 0508 112233
    • Pick up Sat 16 Jan Auckland
    • Drop off Friday 29 Jan Auckland $984+gst + petrol
  • Ford Ranger $475 3 days, $968 week henderson rentals mt wellington, talk to dawn, 09 573 1664
  • Move RAV $275
  • Falcon 984+510+275=$1769 + petrol + $60 flight
  • Rail 489+300 flight = $789 + RAV petrol
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