This is yet another ode to Tesla’s Design and Development Engineers. Here, we pay homage to the clarity of their HV layout – and to the complexity of the coolant regime
First, the HV circuits. The beating heart of the HV systems in the Model S is located under the back seat.
In this shot, the cushion is tipped forward, showing 4 groups
of HV wires leading to the connection box.1.
At the top of the picture, the 4 cables to the
charge point are seen heading across the car and rearwards to the charge point
close to the nearside rear light cluster2.
Next down are the two power leads coming from
the battery3.
On the opposite side of the connection box from
the battery feeds are the two power cables going to the electric motor4.
The last set of cables heading down the picture
and the to the right – and hence the front of the car – are the HV feeds for
the frunk area power supplies, such as the air con unit and coolant heater.
Then we removed the cover of the connection box… dern dern derrrrrr
What surprised us the most was that the battery cables are directly connected to the motor power feeds. On reflection, that makes perfect sense. However, we had expected some kind of contactor at this point……. These two connection posts can be seen clearly in the lower part of this picture.
The four cables from the charging port can be seen here – three phases and a neutral. Meanwhile, the two smaller diameter cables taking HV power to the front mounted ancillaries can be seen.
Almost as exciting for us is the cooling system. This is significantly more complicated than the design for an ICE car. In practice there are two separate circuits here, using just the header tank and radiator in common. The function of the cooling circuit is;-
- Warming up the battery (Given that it warms as well as cools, perhaps we should be pedantic and call it the thermal management system?). The battery charges better if above about 15 degrees.
- Cooling the battery. Ironic eh given No 1 above? You know how your phone or laptop gets warm if you charge it quickly or drain lots of power quickly. The Tesla batteries have very similar chemistry and so do the same. There is that extra frisson of excitement from knowing that above about 130 degrees C, the batteries are likely to have a spontaneous thermal event (that is a FIRE!) Cooling is important!
- Cool the drive motors
- Be warm enough to heat the cabin
- Provide warmth for evaporation in the air conditioning system
To achieve all of these contrasting objectives, the “thermal management system” is very complicated, with lots of pumps and diverter valves.
Conclusion
The HV and coolant systems in the Tesla Model S are complicated but well designed.
So, who agrees that we have covered quite enough about the Tesla Model S reverse engineering? At long long last, we will finally begin to cover the Golf GTi EV conversion next time………