Recently I started designing the rear batterybox. Now I am starting to get better at it and really enjoy it. First I continued working on the rear end of the car, the context of the batterybox.
Next I further worked on the tow bar and added the bumper mounts.
Finally I checked the measurements of the car. The polycarbonate lid of the batterybox will be mountetd exactly on the lowest edge of the spare wheel compartment cover support.
Furthermore I started sketching the batterybox itself.
This is more convenient to do “in context”. However I need to complete the assembly first for which I need some further assistance from Bas.
Designing the front battery box
I also started working on the front battery box which turned out to be quite challenging.
The basis using my wooden prototype was quite straightforward.
My idea is to use rails in which I can slide the modules in from the front end side. I will insert and connect the batteries while the box is not in the vehicle and put it in as a whole. As soon as the batteries are in, the box is closed off with a cover.
The cover creates a flat top surface with a mounting edge together with the main box itself. The polycarbonate transparent lid will be mounted on top of it.
In the mounting edge I will use blind rivet nuts. I will predefine and sketch the exact positions to prevent interference with components within the battery box.
Battery management system
I will use a battery management system (BMS) from Lithium Balance. There will be one local monitoring unit per module and one battery management control unit.
The management control unit and three local monitoring units will be placed in the front battery box. Furthermore I want to add a high voltage fuse and the shunt (measuring the incoming and outgoing currents) there.
To make sure the box can be installed in a safe and convenient way, there will be high voltage connectors on each side (+ and -).
It turned out to become quite crowded and not enough space for the shunt.
I am also implementing a maintenance switch which can disconnect the front and rear battery box. Ideally I’d like to mount it directly in/on the front box, but it is quite large.
There is not much space under the hood left. In the front I need the spacing towards the hood and at the back I need clearance between the wiper washer. I could of course move that to the paravan like the cars until modelyear 1966 have. By extending it the slope of the top needs to be decreased for enough clearance with the hood towards the rear end. However there is not that much space due to the VIN and the DC-DC converter.
The extended version would look like this.
It just fits between the DC-DC and wiper washer but not easily. Furthermore for the components it still is quite tight and I actually don’t like the look and feel. I started exploring a third option with the maintenance switch in a separate attached box. In that way it stays in front of the DC-DC and wiper washer (looking from the right hand side).
This did not result in much more room for the components and the high voltage fuse holder is partly in front of the opening to the switch.
I decided to no longer treat the current DC-DC mount as a constraint. In the end this resulted in the following design.
The maintenance switch and high voltage fuse have a seperate ‘box’ which is lowered a little bit. Therefore there is enough room for the wiper washer, the hood itself and reading the VIN. The fuse now has his own access cover. I will need to cut out the DC-DC mount and weld it in again at a different angle so the plug moves towards the firewall. I am quite happy with that result and need to add the following:
- Cooling connections in/out
- Holes for rivet nuts for the covers
- Widen the box a little bit to create more space for the high voltage wiring
To be continued.