Optimum operating temperature?

2829 Views 7 Replies 3 Participants Last post by SuperSmartie, Jun 26, 2017

InjuredAgain

Discussion Starter · Jun 24, 2017

Does anyone know what the optimum temperature is for the battery pack and for the motor? Is the coolant routed through them in series or in parallel? And if the battery pack needs heating, is it done via some other method than the coolant?

Thanks.

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SuperSmartie

· #4 · Jun 25, 2017

Text Diagram Line Circuit component Passive circuit component

a: coolant loop
b: refrigeration loop

N83: Charger
M5: Motor
N129/1: Inverter
G5: Battery
R101: Battery heater
A9/6: refrigeration compressor

Sadly, this diagram is missing the heat exchanger between the two loops. It sits in the battery coolant loop with the M43 pumps.
@Blaine: Where did you get those numbers for the activation threshold temperatures from? I've long been trying to find that information! The lower one is hard to observe, unless you want to spend the night outside in the dead of winter. I'm sure the upper one is wrong - I have never been able to observe the compressor turning on to cool the battery, and it frequently gets a bit above 30C in the summer.

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SuperSmartie

· #6 · Jun 26, 2017

Thanks for the google docs! Super to have some repository for stuff like this.

Blaine said:
heard the non-cabin fan running

That might just be the radiator fan - doesn't mean the refrigeration compressor is running. The compressor is in the back and makes a distinct whine, but you can only tell from outside the car. The radiator fan gas two speeds. Low comes on when stuck in traffic and the car feels it needs extra airflow. I've only ever hear high when I had an intermittent failure in the cooling system. High makes a pretty good impression of a fighterjet taking off.

Blaine said:
Its hard to imagine that MB would have put all that extra coolant plumbing into the battery if they weren't going to use it to cool the system.

If you mean the AC-coolant heat exchanger and associated valving, there is one case it's definitely needed for: while using the 22kW fast charger over in Europe. That frequently makes the refrigeration system come on to cool the battery, but I haven't gotten any of the guys in the German group to record what temperature it happens at.

Outside of that and Death Valley there may not be much use for this advanced cooling capability.

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SuperSmartie

· #8 · Jun 26, 2017

InjuredAgain said:
But also, our garage never got even remotely warm. It gets really warm and stuffy in the garage when we drive our ICE vehicles in this hot weather and then it has to shed all that heat.

Great demonstration of the amazing efficiency of the electric drive train. All that heat the ICEs produce is pure waste!

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