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Do the motors have a cooling system as well?
Yes, as Cab Driver mentioned the motor generator units are cooled through pressure fed ATF that routes through various cooling channels within the transaxle (including the motors) and then routed out to a heat exchanger built into a portion of one of the radiators. Interstingly the trans fluid pressure comes from a 3-phase high voltage AC motor driven directly from a 3rd inverter channel (the other 2 for MGU A/B of course
Wouldn't the output of that (and possibly the battery cooling loop) be fed into the CHCM as a heat source when cabin heating is needed? If you're drawing a fair amount of power in CD mode, they'll get warm...
While seemingly somewhat more efficient, there isnt a lot of cross-feeding of the various heating/cooling loops. Balancing the mesh of actual heating values and dissipation isnt an easy task. So yes there may be various cooling circuits that are "getting warm" or even HOT that one might think could be utilized for additional cabin heat, but generally they are not implemented for a myriad of reasons.
WOT
 

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This is the kind of detail I have been looking for for about a year re: the heat transfer aspects of the battery. It's extremely technical from a heat transfer POV, We speculated about phase change materials between the cells but not coolant loops. Totally trick from a HT POV.
 

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This is the kind of detail I have been looking for for about a year re: the heat transfer aspects of the battery. It's extremely technical from a heat transfer POV, We speculated about phase change materials between the cells but not coolant loops. Totally trick from a HT POV.
Geo, much of the HT details regarding the battery loop is embedded in the video posted in #76 by Charles Whalen. However while the video nicely shows the 144 parallel flow coolant heat exchangers between the battery cells, it fails to mention the 360V coolant heater and the chiller unit used to cool the battery coolant via R134A refrigerant pumped from the electric air conditioning compressor. (technically in parallel with the cabin A/C refrigerant circuit, but with it's own TXV)
I might be wrong but if I recall a few months back we discussed the potential use of phase change materials within the power inverter module, (although it has it's own coolant loop as well) however I've yet to confirm their presence in the Volt PIM.
More complete details on these heating/cooling loops should be made more available sometime in the very near future. ;)
WOT
 

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At a Volt test drive event today, I asked a drivetrain engineer about the situation I'd postulated above: if the car is left UNplugged and in hot weather, what does the battery TMS do, and what about when it runs out of charge? He said that the car will indeed "cannibalize" battery energy to run the TMS (we didn't talk about exact temperatures). However, it will only do so down to 50% SOC, because at that point they don't care anymore. Apparently at 50% SOC the battery life is essentially unaffected by the high temperature excursions.

From monitoring the Tesla forums and the Roadster's "storage mode", I knew that 50% SOC was a good point for the battery to hang out for a long time, but I didn't know that it also made it resilient to high temperatures. As I've mentioned above, Tesla's battery warranty says "don't do that" when it comes to long-term high-temp unplugged storage, but it appears that GM will make no such requirement. GM may very well have looked at the performance and actuarial numbers and decided it wasn't worth the possible confusion and bad press, even for such a corner case.

And everything I just wrote may not even be right, but that's what I drew from what the GM guy said :)
 

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At a Volt test drive event today, I asked a drivetrain engineer about the situation I'd postulated above: if the car is left UNplugged and in hot weather, what does the battery TMS do, and what about when it runs out of charge? He said that the car will indeed "cannibalize" battery energy to run the TMS (we didn't talk about exact temperatures). However, it will only do so down to 50% SOC, because at that point they don't care anymore. Apparently at 50% SOC the battery life is essentially unaffected by the high temperature excursions.
Very interesting, I hope its true.
 

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While this is technically true. Keep in mind ALL cabin heat comes from heated coolant.When ICE is OFF that heat will come from the electric (PTC) heater that's part of the Coolant Heating Control Module (CHCM). This heater element is powered directly from the 360V source and therefore can heat the coolant passing through it rather quickly. When ICE fires up in extended-range mode this heat is then supplmented with heat from the ICE cooling system, and the balance of coolant flow through these loops carefully controlled by a coolant flow control valve.
HTH
WopOnTour
Are you saying they are using resistive elemnt heating if the ICE heat is not available?? Why not a heat pump??

but in 83 you said it was a heat pump, which makes sense.
 

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However while the video nicely shows the 144 parallel flow coolant heat exchangers between the battery cells, it fails to mention the 360V coolant heater and the chiller unit used to cool the battery coolant via R134A refrigerant pumped from the electric air conditioning compressor. (technically in parallel with the cabin A/C refrigerant circuit, but with it's own TXV)
How much extra length do the 144 heat exchangers add to the battery pack?.. a few inches?.. how are they preventing leaks as the coolant flows into the exchangers?.. I would simplify the design by using resistance heaters at each cell module and just use the heat exchangers to cool off the cells.. I hope all them valves are reliable.
 

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How much extra length do the 144 heat exchangers add to the battery pack?.. a few inches?.. how are they preventing leaks as the coolant flows into the exchangers?.. I would simplify the design by using resistance heaters at each cell
Spoken as a true EE. Herm, you don't have to change your fan belt every 10000 miles anymore. The auto industry has made these mechanical systems very reliable.
 

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How much extra length do the 144 heat exchangers add to the battery pack?.. a few inches?.. how are they preventing leaks as the coolant flows into the exchangers?.. I would simplify the design by using resistance heaters at each cell module and just use the heat exchangers to cool off the cells.. I hope all them valves are reliable.
They are only about 1mm think so I guess they add ~144mm to the total pack length. Testing found the liquid cooling with very high surface area contact to the cells, delivers superior temperature control in both heating and cooling modes. Coolant leakage is always of primary concern in ANY cooling system, but especially so in a hig energy battery pack. You can be sure a significant amount of engineering has gone into their design and implementation.

Also it should be noted that the battery pack is actually divided into distinct 3 sections, each field serviceable seperatly. So should some sort of cell issue arise the entire battery assembly WILL NOT need to be replaced, just the section with issue.
Does the Volt have any fan belts? I can't think of a reason for one, unless they're running stuff off the traction motor.
There is one short belt that drives the mechanical water pump. It has a service interval of 150,000 miles or 10 years whichever comes first.There are numerous pros and cons to maintaining this type of primary coolant pump for the ICE cooling system. The pros prevailed. ;)
WOT
 

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There is one short serpentine belt that drives the mechanical water pump. There are numerous pros and cons to maintaining this type of primary coolant pump for the ICE cooling system. The pros prevailed. ;)
WOT
If using neutral to hypermile and coasting over 70, is there a concern with popping the belt when shifting back in to drive?
 

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Does the Volt have any fan belts? I can't think of a reason for one, unless they're running stuff off the traction motor.
I have a couple of pics that show the 2.. The EV motor is much simplified and very trick. I will try to give a snapshot later.
 

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If using neutral to hypermile and coasting over 70, is there a concern with popping the belt when shifting back in to drive?
Doubtful. I certainly cant see how.
That would require some sort of torque reversal on the water pump drive pully. I't just a simple self-tensioned (stretch) belt and has a service life of 150,000 miles or 10 years (whichever occurs first)

Besides torsional distrubances and vibration from the drive unit back through the ICE are essentially completely eliminated by the damper plate that couples the ICE to the transaxle.
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Charles,
Looks like you intend to monitor the packs internal resistance and use that as a gauge for life degradation. What end point resistance do you use for end of life? Do you also intend on monitoring kwh storage capacity? -GSB
 

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torsional distrubances and vibration from the drive unit back through the ICE are essentially completely eliminated by the damper plate that couples the ICE to the transaxle.
Since you mention the damper, did GM decide that the Volt 4ET50 electric drive unit didn't need the Damper Bypass Clutch that the 2MT70 Two Mode Hybrid had? The DBC was there to make engine startup / shutdown smoother. GM has made no mention of a DBC in the Volt. Do you know? (... and can you say?)
 

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Not to be not-polite, but can we keep this thread on subject=TMS???
 

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Since you mention the damper, did GM decide that the Volt 4ET50 electric drive unit didn't need the Damper Bypass Clutch that the 2MT70 Two Mode Hybrid had? The DBC was there to make engine startup / shutdown smoother. GM has made no mention of a DBC in the Volt. Do you know? (... and can you say?)
Yes, it's there and fully implemented.
WOT
(Sry GSB) ;)
 

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Ok Ok just to contribute to the thread...

As most everyone knows at this point, there are 288 battery cells that are connected in series-parallel.
Three 3.7V cells are connected in parallel and these 96 modules or "triplets" (GMs term) are then connected in series to form the 355.2V pack.

Battery Management and Cell Balancing
The pack is divided into 4 distinct management blocks each with there own group of 24 triplets to monitor. This is accomplished by four interconnected Battery Interface Control Modules (BICM). Each BICM monitors the 24 voltages and 4 temperature probes interspaced between every 6 cell groups. These various input values (there are a few other such as pack voltage, current etc) are communicated to the Battery Energy Control Module (also housed within the battery pack) which then shares the information via the GM-LAN network.This data is analyzed by the system executive and used for cell performance, life estimation, diagnostics AND for "cell balancing" functions.

As discussed here often, it is advantageous to maintain a similar state of charge on each of the cell groups in a large series connected pack. However individual cell chemistry variation, placement within the pack, even temperature variances can result in varying states of charge that can be detrimental to pack life. The BMS observes the individual cell group (triplet) voltages and determines which cell groups have for whatever reason maintained a higher or lower state of charge than the majority of other triplets.Cells will either need energy added or removed in order to maintain the triplets at near an identical state of charge. In that event the BMS then able to activate a transistorized switching matrix within the BICM and is even able to temporarily place a resistive load across a group's + and - terminals in order to pull a high triplet down to a similar state of charge as the rest. This function is performed at various times to (hopefully) improve battery life.

These are the solid state devices seen in the early cutaway diagrams of the battery.

WopOnTour

PS> Lyle is letting me post a battery thermal managment article out on the main page sometime in the next week or so. Afterwards I'll post copies of it here for further forum discussion.
 

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Great to hear about the upcoming BMS article! The "driver information center" messages listing that you posted in another thread raises a number of questions about TMS, in particular how the ICE gets involved, and I hope you'll be able to cover those behaviors in your article.

And, presuming that you have permission, thanks go to GM for letting this technical information out! GM will likely enjoy years of market advantage due to the intellectual property they'll have locked up ...
 
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