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Chevy Volt Battery Cooling Systems & Algorithms

While at the Dublin Chevrolet Open House, I had a chance to speak with Keith Buford, a hybrid powertrain cooling systems algorithm engineer.  We had an interesting and fascinating discussion about the Volt, its development and of course some of the engineering that went into the actual battery and power electronics cooling systems in the Volt.  You can see a nice 8 minute segment of the chat I had with Keith at the bottom of this post. 

As many already know the Volt battery is liquid cooled so as to preserve the longevity of the battery pack.  This is design requirement because lithium ion batteries will degrade rapidly at elevated tempuratures and lose their ability to retain charge permanently.  The strategy here of course contrasts with prior implementations for battery packs where for all other hybrids are typically air cooled  and the Nissan Leaf battery which is also air cooled.

Here are some highlights and insights from the video.

As mentioned before there are 3 seperate Chevy Volt cooling loops and respective radiator stacks.  They are for the internal combustion engine, power electronics, and battery respectively

The Chevy Volt Gas Engine is designed to operate at 90 degrees C (194 F) and is cooled to that level (typical for a gas engine)

The Chevy Volt Power Electronics ideally operates at less than  70 degrees C  (158 F)

The Chevy Volt Battery is cooled to 40 degrees C or less (104 F) 

‘The Actual Lithium Ion Battery is very efficient, Given a roughly 70 F Day, you could deplete the entire battery without it requiring additional cooling (Basically it won’t rise above 104 F)

The Chevrolet Volt Battery Cooling Loop can tap the cooling power of the air conditioning unit on very hot days to condition the battery.

Onstar will play a much more important role in the initial Volt launch to gather additional battery telemetry data (how hot is it getting in your pack)  Obviously they have tested in the Heat of the Desert Southwest, but leave it to a customer to use and abuse it.  (They will know if you cooked your battery!)

Enjoy the video!  If you have any follow up questions, I have a means of trying to follow up for additional information, but of course, only some will probably actually be answered.  Post your questions here if you have any!

3 Responses to “Chevy Volt Battery Cooling Systems & Algorithms”

  1. Michael Gershman says:

    This was the best information that GM put out on the behavior of the battery TMS unplugged in hot weather. Thank you. Unfortunately, it was an interview with an engineer who got vaguer as your questions got more specific. I disagree that most Volt customers would get confused by information like KWH or degrees C. Who does GM think buys a battery-powered Cruze for $44,000?

    I realize that GM considers the details of the TMS algorithms proprietary, but a major car company can put a Volt on a test rig and learn whatever they want. There are also techniques for reading proprietary microprocessor programs right off a PROM chip.

    That leaves the Volt owners like us. It’s important that GM put out a serious written statement about how the Volt’s battery TMS handles 105 degree weather while in a parking lot and not plugged in. I saw the Driver’s Manual recommendation to use a car cover, which I do for 2+ hour stays, but that’s it. It would be nice if the ICE started occasionally, but the car might be in a garage, so the TMS has to tap into the guaranteed 20% of the battery SOC that is held in reserve.

    My service manager got a verbal statement that the TMS can tap into the battery and some customer blogs quote GM people to that effect, but nothing is specific or in writing.

    Since you at least have a phone number into GM, please pass along my recommendations that they get much more specific about how the TMS protects the battery against hot weather when unplugged and that current KWH of charge and battery temperature measurements be available to the driver on the console or iPhone.

  2. Daniel R. Watkins says:

    What video??

    Will the AC run to cool the battery if the car is off, not plugged in and fully charged? What temp will it activate?

  3. Thayne says:

    I’ve been checking my Volt’s Battery temp with a OBDLink LX and MyGreenVolt app on my phone every few hours all afternoon. Its currently 103 degrees outside. It was parked in the shade at my office and it never went above 89 degrees and dropped from 89 to 84 when I drove home from work. It’s parked outside right now in the shade and the temp has raised back up to 87 degrees.

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