[InjuredAgain]

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.

 

[Blaine]

I believe the cooler comes on for the HV battery about 30C and there is also a heater in the circuit that activates at -10C.

The charger, dc-dc converter, motor and power electronics are all cooled with the same system. The chiller for the AC, power electronics, battery etc is interconnected. They all use the fan and condenser at the front of the car.

There are a few loops and valves. The main coolant pump is to the driver side of the charger in the motor compartment.

 

[InjuredAgain]

Blaine, thanks for that information. I was just interested in some general information since I spoke to someone today with a Leaf who experienced pretty serious degradation. They said they noticed it last summer when they would come home with the car hot, and then immediately plug into a high speed charger. There is apparently a tool called Leaf Spy that seems to do what the Odyssey tool does. We didn't have much time to chat, but that did spark my curiosity.

So it seems like a fairly wide but cool range of temperatures is optimal for the battery. I'm glad the Smart's system is well engineered and not just air cooled!

 

[SuperSmartie]

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.

 

[Blaine]

View attachment 31746
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.

I honestly don't remember where the 30C number came from and I haven't spent the effort to confirm the exact trigger threshold. I do know that from looking at the HV temperature sensors after a modest highway run the cooler doesn't come on below 30C. Numbers in the 20's, no AC and no physical indication of fan etc. Similarly, after extended highway runs I'm fairly sure that the cooler does come on because I've pulled the car into the garage and heard the non-cabin fan running while everything else was off, but the car was still 'on'. The noise profile is quite different.

For everyone else: those temperatures are *internal* battery temps. There is a temperature sensor per stack in the battery pack.

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. I suppose you might get some convection effect, but that also seems unreasonable. Plus the coolant pump is fairly large.

I'm sure my coolant pump is working because it leaked and I had to get the gaskets replaced. The service tech cleaned and ran checks on it so I *assume* that they made sure it was moving coolant. The AC is definitely working.

The -10C is from a partial tech sheet that someone posted. According to the notes it's only applicable while the car is on external power. Interestingly, that diagram is slightly different from the one you posted and it does show more interconnects.

There is some anecdotal evidence that in really cold conditions (-32C ?) that something warms the battery or fools the BMS. There have been a few posts where people said the car was "dead" when they tried to start it but if they waited with the key 'on' then it would eventually start up. Maybe that was just their bodies warming the cabin up, but :shrug:

You can find the 451ED related manuals pubs that I've collected in a google docs folder. including the other diagram. I'd love to gather more stuff if anyone wants to share.

We're getting into the warm weather here so I'll be able to hook up the battery tool and do a bit more monitoring. If work slows down maybe I'll get the time to build out more extensive logging features.

 

[SuperSmartie]

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

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.

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.

 

[InjuredAgain]

We had a nearly 100 degree F. day today and I drove the Smart hard before garaging it. When I plugged it in to charge, I couldn't hear any noise that sounded like a pump or compressor. I had it in 74 HP mode for a fair amount right before parking it.

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.

 

[SuperSmartie]

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!