emini

My friend Philip had something of a setback in his electric race car project and has launched Tumanako, an open source electric car effort, in the hope of completing what couldn't be bought. I've been working on the BMS as I wasn't happy with any of the commercial offerings -- basically they were either too expensive or too opaque. When we're finished, the Tumanako BMS will provide valuable insight into the health of your battery. You won't one day get a red light and have no idea or information or history about what your battery was doing before something went wrong.

I'm converting Bob's assembly firmware to C. The BMS uses PIC processors and it's been about 10 years since I last played with them. A lot has changed. I've made quite a lot of progress in the last week or so, I

• modified a single pair RS485 - RS232 converter to work with a dual pair network
• made a cable to connect my programmer to the port on the BMS boards
• assembled Bob's original firmware
• wrote a new firmware in C which, so far, flashes lights in response to characters on the RS485 bus

The photo above shows one BMS slave board, capable of monitoring 5 cells, mounted on top of 5 A123 M1 cells in a test rig. The empty looking circuit board is a shunt board which holds the transistors to control the balancing current. The small circuit board with plugs at either end is the RS485 - RS232 converter. I don't have a photo of flashing lights and programming cables for you today, I'm sure if you try, you can imagine something approximating a christmas tree.

In New Zealand, we pay a petrol excise duty which helps pay for the roads and traffic accidents. No such duty is charged on diesel, instead you pay per kilometre, depending on how much your vehicle weighs. The law is written such that any vehicle consuming fuel not taxed at source must pay road user charges. Since electric vehicles consume electricity which isn't taxed, they must pay road user charges. The per kilometre charges on my vehicle are more than the cost of the electricity.

This is changing, starting in October electric vehicles will be exempt. The exemption will expire in 2013, which is probably a good thing -- if electric cars take off, there would be a big hole in the ACC & Roading budgets. It would seem that we need to thank Hon. Dr. Nick Smith, MP for Nelson and owner of a Hyundai Electron.

I took my car to show the students at my old primary school. I had half an hour with each of three classes as part of their science curriculum. The children were exceedingly interested and very positive about electric cars. I did have some rough ideas about what I might tell them but they ended up asking so many great questions that they basically led the discussion. I took a short 50²mm battery cable and a 150A 500V fuse to pass around, and I showed them a 10Ah LiFeBatt cell, an 18650 laptop cell and one of the Thunder Sky cells from my car. Before I went, I spent an afternoon cutting a polycarbonate cover to go over the battery -- I didn't want any small hands getting a shock.

If anyone is interested in starting something like B*E*S*T Outreach, get in touch, these students would be very keen.

Many thanks to those on the EVDL who gave advice on what to say.