Last week while working on my front battery box and cooling design I thought I made quite some progress. I thought I had actually taken some design decisions and reduced the degrees of freedom. The opposite turned out to be true!
I received some input from Martijn (who converted a Volvo 240), continued to discuss my cooling system with Ben. Furthermore Daniel (from who I bought my Tesla modules) shared some of his thoughts and once more I talked to Anne from New Electric for some additional input. Thanks to you all!
Redesign cooling system
I had created the basis of the cooling system earlier. In the meantime I did some simplifications. I added the battery heaters in series in the same loop instead of two separate ones. Saves a thermostatic mixing valve. Furthermore I am going to test whether I still have enough flow when I add the heat exchanger to that loop permanently. That would save a 3-way valve. Finally I am going to set the front and rear battery box in parallel for a more even temperature distribution. This is the intended scheme:
The DMOC 645 controller and DC/DC will no longer have a dynamically controlled pump but a smaller pump that always runs at 100%. The temperature sensor intended for that loop will now be used in the battery circuit.
Redesign highvoltage diagram
After talking to Anne I concluded to to be using the Rebling connectors he provided me with earlier. Main reason is concerns for EMC compatibility. The connectors have plastic covers which do not shield. Instead I will be using metal gland nuts that are big enough to insert a cable with crimped lug nut.
The good news is that is gives much more space in the battery box. I will be using a main contactor in each battery enclosure. This enables the BMS to disable the whole system without any high voltage on cables outside the boxes. Building on the Lithium Balance CHAdeMO fast charge documentation I started designing. First on paper.
In the end I decided to ad the main – and charger contactor to the front box and the main + together with the precharge contactor to the rear box. New Electric did have a Givavac GX14 contactor available which is a little more compact than the TE one. The updated diagram will be:
This was I do have an extra cable coming out of the front box, but the advantage is I do not need a midpack contactor.
Redesign battery box
All of that resulted into a redesign of the front battery box. I tried mounting the fuse holder onto the side. Then I all started to fall into place. The extra ‘box’ could be reduced in size and I could flatten the box as a whole.
Within the box I’ll be using the same 35 mm2 shielded cable as I will be using underneath the car. They are not easily bendable. In the documentation I found that the minimum bend radius is 45mm. So it was about time to add those to the design too.
I will connect the shunt and contactors using a custom copper busbar.
Now it starts looking like a more or less final version (but that’s what I thought one week ago as well).
To do is optimising the BMS board layout.
Inspiring example: Jaguar E-type Zero
Finally I came accross a very nice an inspiring example: the Jaguar E-type Zero.
All photo credits Jaguar Landrover
This will be shown at the Jaguar Land Rover Tech Fest in Londen. Impressive conversion! The basis was a fully restored vehicle from 1968 which now has 200 kW of power, goes from 0 – 100 in 5,5 seconds and with the battery pack of 40 kWh has a range of 270 actual kilometers.
A real ‘high end’ conversion. Would be nice to see it in real life.