A few weeks ago I was invited onto Radio New Zealands Saturday morning show. If you are interested you can listen to the interview here: http://www.radionz.co.nz/national/programmes/saturday/audio/201762024/stefan-andreas-meyer-open-source-electric-car
One of the key things we wanted to show with this project is that a conversion can be done without disabling the car. Of course that’s not entirely possible but I think we came close enough: for installing the system the car was rendered not drivable for about 36 hours. That leaves room for improvement but was a good start I think …
It took a while to finish off all the last little details and especially the programming of the inverter. But a couple of weeks ago we finally got the o.k. from LVVTA so that the car is now officially certified and road legal. The process of writing up the plans and figures for the electric drive train is already well under way so that I hope to be able to put them online within the next couple of months.
One of the hick-ups we discovered on our first test-drives was the fact that the motor was generating more torque than we could transfer with one v-belt. As a consequence we built an extension of our current coupling mechanism allowing us to add a second drive belt thereby doubling the torque capacity. The video below shows how we used Roberts CNC-mill (in a rather unconventional setup) to grove the pulleys.
The last 2 months were quite busy with working on little but important details: the ethernet cables from the battery boxes to the battery management system had to be upgraded to Cat6 which meant that I had to disassemble and reassemble the battery boxes again. We had to finetune mechanical details on the battery boxes as well as on the adapter-plate for the electric motor. A separate vacuum system had to be installed to insure that the brakes work even when the petrol engine is not running. And then of course the automation of the charger: going from full speed to a trickle to a complete shut-down as the batteries reach their maximum voltage. After doing all this we were finally able to put all the components in the car last weekend and even though we ran out of time to connect and test it and I had to drive off with the petrol engine I was quite happy with the progress and look forward to testing the electric drive tomorrow
getting the motor up into its designated space proofed to be the most challenging task;
It’s one thing to build a nice box but quite another to get all the gear in. The space is so confined that it took me many hours get all the cables in and tighten the various elements to the frame. But the end result doesn’t look to bad I think …
In the end the mounting system for the battery boxes looks fairly simple but it took us a while to come up with a solution that didn’t require us to drill into the main beam of the car (big No-No). It involved a lot of measuring, re-measuring, test fitting etc. But it looks quite nice now: on the top left the 10 mounting brackets (5 for each box); on the top right the space under the car (between the wheels) with the aluminium blocks to which we can attach the the mounting brackets; on the bottom one of the battery boxes as it will be mounted;
Following Patrick’s advice (he’s our electrical engineer on the team) we made one aluminium box that has space for all the electronics: the contactors, the 3-phase inverter, the chargers, the BMS system and the rectifier diods. The latter will enable us to use the inverter to fill the batteries in charging mode and since they can warm up quite a bit they are mounted on a heatsink. Also on Patrick’s advice we changed these diods to fast recovery ones and with the oscilloscope we saw that they performed nicely