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Volt thermal management system temperature band?

172K views 184 replies 38 participants last post by  ganicuss 
#1 ·
Does anyone know the temperature band, and the average or optimal temperature within that band, that the Volt’s thermal management system keeps the batteries at?

For instance, the Tesla Roadster’s thermal management system, which also uses a liquid-based heat exchange method, keeps the batteries between 24C and 48C and at an average temperature of around 35C (at least here in my hot climate), which is about my daytime ambient, or just slightly above.

That 35C average temperature that the Roadster’s battery pack is maintained at by its TMS goes a long way towards explaining the 4 to 5 year expected pack life in a hot climate (and 3-year battery pack warranty). The Volt, on the other hand, has an 8-year battery pack warranty, and my understanding is that expected pack life in a hot climate should come close to that, except under some extreme circumstances. (1)

Though of course the Roadster’s and Volt’s battery packs have different cathodic chemistries -- LiCoO2 and LiMn2O4, respectively, those are both at the higher end of the heat sensitivity/degradation spectrum among the various lithium cathodic chemistries.

Given the difference between the Volt battery pack’s expected 8-year calendar life and the Tesla battery pack’s expected 4 to 5 year calendar life (in a hot climate), together with the 35C average temperature that the Tesla’s TMS keeps the batteries at, Arrhenius curve profiles relating battery life to long-term temperature exposure would lead me to deduce, or guess, that the Volt’s TMS might keep the batteries at an average temperature of somewhere around 21C. But I’m just wondering if anyone knows this for certain and what that temperature actually is?

Another thing I’m wondering is ... Does anyone know how much energy, i.e. how many kWh, on average, the Volt’s TMS consumes per day to run itself, to maintain the batteries at their optimal temperature and/or within the desired temperature band?

(Of course this might vary to some extent regionally/climatically and seasonally, as well as be dependent on specific conditions and circumstances, such as amount of solar loading exposure, availability of a climate-controlled garage, etc.)

For instance, when the Tesla first came out, its TMS was consuming around 10-12 kWh per day. The company was later able to damp that down to around 3-4 kWh per day (albeit likely at the expense of a higher optimal/average temperature and/or wider temperature band/limits).

I’m assuming that under extreme conditions, such as in a hot climate, and especially if exposed to significant solar loading on a daily basis (typically 50-60C), one would want to keep the Volt plugged in at all times, whenever the car is parked and within reach of an available 120V outlet or Level 2 EVSE, so that the Volt’s TMS can run itself on offboard power, rather than having to power the TMS from the batteries themselves. Does anyone know if that is indeed the case -- that the Volt’s TMS can and does power itself from offboard power whenever the car is plugged in, whether charging or not (i.e. before, during, and after charging)?

***

*(1): The kind of extreme circumstances under which the Volt’s battery pack might be expected to have a shorter life than 8 years could, for example, be the following type of scenario:

A Volt owner lives in a hot climate and has a 40-mile commute each way, 80 miles round-trip. Running the air-conditioning on his morning commute, he arrives at work each morning with the battery pack fully depleted, at 30% SOC, having just entered charge-sustaining mode. There are no 120V outlets nor Level 2 EVSE to plug into at work. Nor is there any shaded parking, so he has to leave his Volt baking out in the hot blazing sun, subject to 50-60C solar loading, every day. Having a fully depleted battery, with no reserve capacity above 30% SOC to run the TMS, nor any offboard power available to run the TMS, the liquid-cooled/water-chilled TMS can’t operate during the day while he’s at work.

The Volt’s well-insulated, sealed battery compartment will, of course, slow the rate of heat conduction into the battery compartment from the 50-60C interior of the car. Yet battery temps could possibly reach 32-38C by 5pm. ... Whereas, in contrast to a Nissan Leaf, not having an active TMS, under the same circumstances the Leaf’s batteries might get up into the 42-48C range. (2)

The Volt’s liquid-cooled TMS will then start back up and run on the 40-mile evening commute back home in charge-sustaining mode, with the gasoline engine providing the energy both to drive the car and run ancillary systems like the TMS. But the battery pack would likely spend at least a few hours each day exposed to elevated temperatures, above the presumed desired temperature range at which the TMS would optimally like to keep the batteries. Over time this will take its toll in a faster rate of degradation, possibly resulting in the batteries having a shorter life than 8 years.

Andrew Farah and Bob Lutz have both referred to this particular extreme example as the kind of worst case scenario representing the type of application for which the Volt is not well suited and an individual in this situation would be best advised that the Volt might not be right for him.

*(2): The Leaf has a reasonable TMS within the limited scope of what it is designed to do -- which is just to dissipate operationally-generated heat. With the way the battery cell form-factor and packaging, as well as the layout of the battery compartment and materials used, are all designed, it should do that quite well. However the Leaf’s passive TMS can only dissipate and shed operationally-generated heat down to the environmental temperature. The lack of an active TMS means that it cannot reduce battery temps below the environmental temperature, which in a hot climate combined with 50-60C solar loading, may well be up in the 40-50C range during the daytime.
 
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#104 · (Edited)
The battery cells are grouped together into three "serviceble" sections.
The first 90 cells (30 cell groups/triplets) make up battery section one . This section is adjacent to the cowl and contains battery groups #67 through #96 and managed by BECM 1.
Battery section two is located behind section one. It is made up of 72 cells (24 cell groups) and contains batteries #43 through #66 and managed by BECM 2 .
The transverse battery section is section number three, it is made up of the remaining 126 cells (42 cell groups) and contains batteries #1 through #42 and managed by BICM 3 and BECM 4.

BICM 1 managing 30 triplets has 5 temperature sensor probes
BICM 2 managing 24 triplets has 4 temperature sensor probes
BICM 3 manages the passenger side of the transverse "T" section (24 triplets) has 4 temperature sensor probes
BICM 4 manages the drivers side of the transverse "T" section (18 triplets) has 3 temperature sensor probes

WOT
 
#105 ·
BICM 1 managing 30 triplets has 5 temperature sensor probes
BICM 2 managing 24 triplets has 4 temperature sensor probes
BICM 3 manages the passenger side of the transverse "T" section (24 triplets) has 4 temperature sensor probes
BICM 4 manages the drivers side of the transverse "T" section (18 triplets) has 3 temperature sensor probes
Thanks WOT. I'm looking forward to your upcoming front page post.
 
#106 ·
Triplet balancing

Per Wot the BMS balances triplets, and these triplets are the lowest level of instrumentation in the pack. An interesting scenario develops if one of the cells goes bad within a triplet. During the charge cycle this triplet with one bad cell would presumably be charged up to the proper, max voltage earlier than most so the BMS would terminate charging of this triplet early. Once the entire pack is charged, and the Volt is on the road in EV mode, this triplet would hit it's min voltage earlier than the other healthy triplets in the pack.

Hmmmm, so what happens then??? At this point we need to stop discharging that bad triplet or we will damage the good remaining cells by discharging them to tooo low a state. Looks like the only option is to switch this triplet out of the series string. Sooooo:

Question: Is the Volt BMS able to switch out triplets from the series string during the discharge cycle.??? Must be.
 
#107 ·
Hmmmm, so what happens then??? At this point we need to stop discharging that bad triplet or we will damage the good remaining cells by discharging them to tooo low a state. Looks like the only option is to switch this triplet out of the series string. .
I think it was mentioned months ago the Volt would have this ability, you would need a 2P2T relay to bypass each triplet in the series chain, not too likely.. probably what they do is is bypass one of the four groups instead, and trigger a low reduced power emergency mode, and a trip to the dealer. The BMS will attempt to balance out any triplets that dont have the same voltage as the others but eventually the computer will light up the service light in the dash.
 
#109 ·
Just a hint of an incipient failure will prompt a trip to the dealer, its an expensive pack and they do catch fire on occasion. The dealer installs a refurbished pack and your packs goes back to Holland for repairs. Will the dealer keep a spare pack?.. I doubt it. How long will it take to ship a pack to the dealer?.. probably a week by truck.

Can a Volt pack be shipped thru air freight?
 
#111 ·
From the SAE feature about the Volt, page 21:

... 'the delta between 70°F (21°C) and 90°F (32°C) can be critical to battery life,' [Frank Weber] asserted. The battery is designed to work while plugged in, at temperatures from -13°F (-25°C) to +122°F (+50°C).
Not sure if we'd heard that yet, but there you go.
 
#112 ·
I read that too, and thought it said something about where they maintain the temp band. But I don't think it does, other than to say it maintains some good temperature with ambient anywhere between -25 to +50. Based on that text alone, that could be an internal temp of 15, 20, or 25. And that could be +/-1 or +/-5.
 
#113 · (Edited)
I’ve got some more information about the TMS, its parameters, and modus operandus, from a long, extended conversation I had on this topic with one of GM’s Volt engineers.

1) When either a) the car is on, or b) the car is plugged in and charging: the TMS operates continuously and keeps all the battery cells in a narrow temperature range between 20C and 22C. If the car is plugged in and charging, it uses offboard grid power to run the TMS. If the car is on, it uses onboard power from the battery itself to run the TMS.

--------

2) When either a) the car is off and not plugged in, or b) the car is plugged in but not charging (i.e. either prior to commencing a timed/programmed charge or after having completed charging but still plugged in):

If the battery pack is at very high SOC, from 85% SOC (top of the charge and top of the Volt’s usable SOC range) down to around 75% SOC, the car’s electronics will wake up the TMS periodically, around once every half hour, to see if the TMS needs to run. If the battery pack is below about 75% SOC, the TMS never wakes up and never runs.

In the 75-85% SOC range, when the car’s electronics wake up the TMS every half hour or so, the TMS checks all the cell temps and does the following:

i) If all the cell temps are below 22C, the TMS does nothing and immediately goes back to sleep (no matter how cold the battery temps may be).

ii) If any of the cell temps are above 22C, the TMS runs for as long as it takes (unless and until the battery pack falls below 75% SOC) to cool all cells down into the 20-22C temperature band, then shuts off and goes back to sleep for another half hour.

If the car is plugged in but not charging, it uses offboard grid power to run the TMS. The TMS could easily run for several days or more in this mode, waking up every half hour to check battery temps and keeping all cells below 22C, under a scenario where the car is fully charged and left plugged in and parked for a long time.

If the car is off and not plugged in, it uses onboard power from the battery itself to run the TMS. Once the battery pack drops below 75% SOC, the TMS will no longer run and goes to sleep and won’t wake up again, no matter what happens with the battery temps, however hot they may get.

If your morning commute is more than about 6 miles (and you don’t have any place to plug in and charge at work), then the TMS won’t operate at all during the day while parked at work, no matter how hot the battery temps get. If you leave home on a full charge and your morning commute is very short, 4 miles or less, then there should be enough reserve above 75% SOC for the TMS to operate for a few-to-several hours during the day, depending on environmental conditions (ambient + solar loading).

As Frank Weber and others have noted, there is a substantial lifetime difference between 21C (70F) and 32C (90F) in the lithium-manganese batteries (which have the highest heat sensitivity/degradation profile of all lithium battery chemistries) that GM is using in the Volt. At 60% SOC, lithium-manganese batteries have a little over 8 year life at 21C (70F) but only a 5 year life at 32C (90F). At higher states of charge, the heat sensitivity and degradation rate is even greater.

What is not yet known, or been revealed, with any degree of specificity in a quantifiable way, is the degree to which the sealing and insulation of the Volt’s battery compartment slows the rate of heat conduction and radiation into the battery compartment from a 120-140 degree F solar-loaded car interior and surrounding pavement. This can only be determined, checked, and verified through the use of a MDI/GDS, if one is able to procure this tool and software, as I am going to attempt to do.

In the absence of that, unless and until one can score a MDI/GDS, for a Volt owner who lives in a hot climate, has a morning commute longer than 4 miles, no charging availability at work, and no shaded parking but rather has to park out in the blazing hot sun, the failsafe procedure to absolutely guarantee adequate cooling and thermal protection of the battery pack, to ensure long (8 year minimum) battery life, is to leave the car powered on, with the doors locked, during the day while at work, so that the TMS can operate continuously throughout the heat of the day. (This is a procedure that a number of first-generation EV owners in hot climates are well practiced in and why they carry an extra key.) This procedure (of leaving the car powered on during the day while at work) should not be done if one’s morning commute is longer than about 33 miles, as in that case the continuous operation of the TMS could possibly draw the battery pack down to 20% SOC (the bottom of the usable SOC range) before the end of the day, reaching the CS-mode threshold, thereby causing the engine to start and run unattended, which would be environmentally irresponsible as well as possibly even illegal in some locales (to leave one’s car engine running unattended).
 
#114 ·
It looks like the Volt should have a user-configurable lower-bound on the battery SOC for TMS rather than having a fixed 75% level. Leaving the car turned on as Charles suggests might be an acceptable hack for an obscure low-volume vehicle but it's an invitation to theft for criminals in hot states with a hopefully higher-volume car like the Volt which they may learn to target.

Let's hope they can fix that in a software update....
 
#115 ·
Sounds like GM may need to add another mode, call it "hot climate mode". Basically, it would do the same function as leaving the car powered on for thermal management, but would disengage the engine start. In this mode, the car could also operate in a pseudo "mountain mode" to ensure a higher battery SOC to maintain the TMS over an 8-10 hour period. Once the SOC drops to a min level, the TMS would go into sleep mode.
 
#116 ·
(Apologies for the length of this post, which requires that I break it up into two separate posts.)

Well, I guess all of this probably shouldn’t come as too much of a surprise, simply because GM Volt senior engineers and managers, from Andrew Farah to Bob Lutz, have been pretty clear in their statements pointing to the fact that GM wasn’t going to be as aggressive as it could have been -- and maybe should have been, at least for hot-climate operation -- in the implementation of its TMS regime.

As far as technically-savvy early adopters having to be a bit flexible, creative, and resourceful in adapting such workarounds (or “hacks”, as you referred to them), you should understand that that just comes with the territory of where we are right now. The EV pioneers of the last decade have had to be even more creative and make even bigger adaptations, workarounds, and hacks. This one here is quite mild and tame in comparison, more in line with an evolution -- and commensurate technological refinement one would expect -- from the pioneer stage to the very early adopter incipient stages of fledgling commercialization which we are now moving into, where nevertheless there will still be some of these types of infancy “teething” issues to work through. At least I won’t have to string ice bags over the top and sides of the car, hanging down over the quarter vents, or rig up a Rube Goldberg robo-chiller on wheels with home-made ducts, as Gen 1 EV drivers have had to do (and are still doing) in hot climates. Even as a work-in-progress with a few infancy issues yet to be sorted through and design and implementation of some of its subsystems yet to be tweaked and perfected, the Volt is still light years ahead and a quantum leap improvement over the Gen 1 vehicles that many of us are still driving, with their 15-year old technology. Let the perfect not be the enemy of the good, as the old saying goes.

You kinda have to take a step back and look at the longer term perspective here and realize that we are in the very, very early developmental stage of lithium-powered EVs. By buying a first-model-year Volt (or a first-model-year Leaf, for that matter), you have to understand and accept that as a very early adopter, the bargain you are making, and the adventure that you are willingly undertaking, is to basically be an extended beta tester for the avant-garde, technologically-leading-edge automakers (principally GM, Tesla, and Nissan) in their early developmental process of their first-generation lithium-powered EVs and to assist them in their ongoing learning process in that regard. This is a very exciting time and that is an exciting role to play, but you also have to understand and be willing to accept some of the risks and responsibilities that come with that. These three leading-edge automakers are taking enormous risks by doing this and making these second-generation EVs, with commercial intent and commitment this time, on this second go-round, but without a demonstrated, proven market for them; and we early adopters have to likewise be a partner with them and be willing to take a few (much smaller in comparison) risks on our end too. It’s very much a shared-risk and shared-adventure partnership in that regard. Above all, it really properly requires a highly-educated and technically-savvy early-adopter customer to undertake this role, so that you go into it with your eyes wide open, well informed on the various infancy issues that you might face and have to deal with, and that indeed, you should have some flexibility, creativity, and resourcefulness to occasionally adapt a few workarounds (or “hacks”) when needed, to deal with such “teething” issues.

Speaking from a decade of EV industry experience, having come at this and seen it from all sides and angles of the industry -- professionally, from having been on the OEM side of the fence, to working with battery manufacturers, to the charging infrastructure side, to public advocacy, the public policy arena and writing legislation, as well as consulting and advising governments and corporations on EV, battery, and charging infrastructure technologies, and last but not least, especially from the consumer side of the fence as a longtime EV owner and driver -- what I can say with certainty (because I have seen this before) is that GM will learn a lot more about lithium battery degradation and ageing, with respect to long-term heat exposure, over the next several years from the accumulated data of the real-world experiences of its Volt-owning customers in hot climates than it ever could, and did, from trying to extrapolate: i) a few weeks of driving a small captured test fleet of production validation vehicles around Death Valley, and ii) simulated accelerated heat/degradation bench testing in the lab. Those latter two can never capture the variety, diversity, and range of experience out in the real world, as well as just the fact that battery degradation and ageing in an EV is a phenomenon that can only really be properly understood by actually observing and experiencing it through living with, using, charging, and driving EVs, and caring for their battery packs, on a daily basis, day in and day out, continuously over a period of several years.

The Volt early adopters will teach GM a lot about lithium battery degradation and ageing over the next several years. There is much that GM will have to learn about battery degradation and ageing that longtime EV drivers already know, having learned from their own experience over the last decade. So to follow up on, and second, the comments in the two previous posts ... yes, the Volt’s TMS is one area where I think we could possibly see GM make some tweaks in its implementation. The good thing, as you said, is that such tweaks should be relatively easy to make by apparently needing just to change various control module software configurations and parameters.

From my perspective of having a good deal of real-world experience (more than GM) over a number of years with hot-climate EV battery performance, degradation, and ageing issues, upon initial reflection I might be tempted to conclude, from what we now know, that the TMS implementation regime in the Volt is a bit weak and represents a design deficiency, at least with regard to hot-climate operation. However that would really be premature, so I will refrain from making that call and will withhold judgment on that for now, at least until I can specifically determine and quantify the degree to which the battery compartment’s sealing and insulation slows the rate of heat gain (from external environmental forcing) into the battery compartment. That is really the crux of the matter that this whole thing hinges upon. All we’ve got at this point is a vague, fuzzy, general assurance from GM that the battery compartment’s sealing and insulation does a “pretty good job” in that regard, but nothing specific in terms of real, hard numbers. I think it’s entirely possible that that is indeed the case, but I wouldn’t be willing to roll the dice and blindly bet a precious $10k battery pack on that without independently checking and verifying it for myself, in my own case and under my own set of local circumstances and conditions. GM actually probably can’t give any real, hard numbers to quantify this in any universal way, simply because there will be so much climatic and other variation factors from region to region, and within regions, from one location to another and one person to another, depending on one’s specific conditions and circumstances.
 
#166 ·
From my perspective of having a good deal of real-world experience (more than GM) over a number of years with hot-climate EV battery performance, degradation, and ageing issues, upon initial reflection I might be tempted to conclude, from what we now know, that the TMS implementation regime in the Volt is a bit weak and represents a design deficiency, at least with regard to hot-climate operation.
With all due respect sir, you seem a bit hung up on yourself, and you, one person, purport to know more than all the combined talent at GM. You say the TMS implementation is a bit weak. Compared to what? The Nissan Leaf's TMS? There are always tradeoffs, and yes, there is always continuous improvement in any technology over time. I suppose one could leave the TMS running all the time in Phoenix and the Volt would be not not have much range left and would be not much different than the typical gas burner.

Your recommendation to leave the car running is just purely irresponsible. Any stolen car is much more likely to be involved in an accident, so your advice is a danger to public safety. Just because none of the few prior-generation EV's were stolen to your knowledge, this is perhaps more a statement of perceived desirability of EV's by the public than a future guarantee. Vehicles have finally progressed to where they can deter the casual joy rider, if not the determined thief. You just have to look at the early Saturn's theft rate once word got out how easy they were to steal, because security was not a concern when picking the lock suppliers, which differed from the rest of GM.
 
#117 · (Edited)
(Follow-on continuation from previous post, immediately above)

Looking at the lithium-manganese battery life relationship to temperature, my own personal judgment and comfort level is that I would draw the line at a 2C rise above 22C, so up to 24C, for the temperature rise and level, respectively, that I would find acceptable and tolerable after 8 hours of intense 120-140F solar-loading/environmental forcing on the battery compartment exterior (with the car being turned off). If at 5-6pm the battery temps are 24C or less, that would be an acceptable heat gain and exposure level that would lead me to conclude that the workaround procedure of leaving the car on all day long is not necessary. If, however, on the other hand, battery temps exceed 24C upon initial boot-up of the car at 5-6pm, after baking all day long in the blazing hot sun (with the car turned off), then that would be unacceptable and would constitute -- in my judgment, for my particular case, conditions, and circumstances -- a clear design deficiency in the TMS implementation regime that would present a compelling case and argument for following the workaround procedure of leaving the car turned on all day long as a routine matter of standard practice.

As I mentioned in my previous post, the only way to determine and measure this is with a MDI connected to a laptop running GDS, which one would need to find and procure. The MDI is apparently a bit easier to source in the aftermarket, but I’ve been told that GDS/GDS2 is the hard part and that it is difficult to near-impossible for an individual without a GM commercial relationship to get a GM TIS online account required to access, download, and once a week renew the weekly lease on, the GDS/GDS2 software. So we’ll have to see about that.

In the absence of that, unless and until I can acquire MDI/GDS, the conservative, prudent course of action and appropriate early-adopter/owner risk management and mitigation strategy to pursue, as a practical matter, would be to follow the precautionary principle and operate on a working assumption, of a less than best-case/most-rosy scenario, that the current TMS implementation regime might be suboptimal, and not as aggressive as needed, for operation in a hot climate, and thus to adopt the failsafe workaround procedure of leaving the car turned on all day long, while parked out in the hot sun. Indeed, statements by GM Volt senior engineers and management seem to support this interpretation and augur caution along these lines. To do otherwise, and just blindly assume a best-case/most-rosy scenario, without any independent verification and actual measurement to check and see whether that holds up and is indeed the case, would be foolish.

With regard to the potential car theft concern you mentioned, I’m not really worried about that and don’t see it as a problem, simply because we have already been doing this for years now -- leaving our EVs turned on, with the doors locked, for the exact same reason (due to TMS design deficiencies, suboptimal for operation in a hot climate) -- and have never had any kind of attempted theft issues arise out of this.
 
#118 ·
Apparently the Leaf manual has become available. Folks on the ev mailing list at work are commenting on it this evening. Purportedly from the manual:


The Nissan Leaf Warranty Manual says on page 9:

GRADUAL CAPACITY LOSS
The Lithium-ion battery (EV battery), like all lithium-ion batteries, will experience gradual capacity loss with time and use. Loss of battery capacity due to or resulting from gradual capacity loss is NOT covered under this warranty. See your OWNER'S MANUAL for important tips on how to maximize the life and capacity of the "Lithium-ion battery."
To which a coworker and friend replied:

The whole MyNissanLeaf forum had a field day on this.

I read the so-called "warranty" and concluded that it reads like:
"Dear Sir or Madam -- we have no idea how these batteries will perform in the real world. Please consider leasing."

I was going to lease anyway, but with a warranty like that, you'd be nuts to buy.
Charles? Good call!
 
#121 · (Edited by Moderator)
So, an increasingly common question around here is something like:

"It's 13 degrees outside, is my battery OK?"

With this post, I'm going to try to capture the temperature thresholds where the different modes kick in. This data is NOT official! It's just what I've gathered from reading various sources.

It's important to note up front that we are talking about the temperature of the battery pack here, not ambient temperature. It's a 400 pound battery pack, well insulated, so it is going to take a long time to cool down / warm up to whatever the ambient temp is. An overnight park, even in a mode where the TMS isn't kicking in, is not necessarily long enough to get the pack to ambient. So an overnight low of -13 F doesn't mean the battery pack itself will actually cool down to that cold!

Code:
Volt battery temperature management system (TMS) modes

Avg Cell Temp range | Volt is parked       | Volt is powered off  | Volt is powered on
                    |  and plugged in      |  but NOT plugged in  |  (e.g. being driven)
--------------------|----------------------|----------------------|----------------------
                    |                      |                      |
above 164 F         | passive cooling      |                      | car won't run (HV contactors opened)
                    |                      |                      | until battery is cooled below 164F 
                    |                      |                      |
164 F .. 113 F      | active cooling*      |  No Active TMS       | active cooling(1*)
                    |                      |                      |
 113 F .. 90 F      |active/passive cooling|                      | active/passive cooling(1*)
                    |                      |                      |
 89 F .. 73 F       | no action -- ideal temperature band for long-term life
                    |                      |                      |
 73 F .. 25 F       |                      |                      |
                    |                      |                      |
 25 F .. 14 F       | warming              |                      | warming(2)
                    |                      |                      |
 14 F .. -13/22 F   | warming              |                      | warming(2)
                    |                      |                      |
below -13F          | warming              |                      | vehicle won't move
(2011-12)           |                      |                      |"Battery Too Cold Plug In To Warm" DIC message
below -22F (2013+)  |                      |                      |until plugged in and battery is warmed by 360V                                                                        battery coolant heater(2)



- Notes:-
independent hot ambient temperature TMS data collection by gm-volt member George S. Bowler 
See front page article for more info: http://gm-volt.com/2013/05/03/volt-battery-thermal-management-system-in-the-hot-arizona-sun/

* active cooling = HV A/C compressor ON
(1) At extreme high temps, the ICE may come on to generate power for the TMS to work faster,
  but only if the car is powered on (that is, the ICE won't start by itself, unmanned)
(2) At low temps, the ICE may come on to heat coolant for the cabin heater, but only if the car is powered on (that is, the ICE won't start by itself; it will  only start once the car is powered on or it receives a remote-start command);  the ICE will shut off once
  it reaches 150 F.  Note that the ICE coolant can not be used to directly heat the battery because the
  battery coolant loop is separate.
The above is for regular operation. If you are putting the Volt into storage for an extended period, without plugging it in, the manual says (on page 10-25) that ideally you should store it where the temperature range will be within 14° F .. 86° F. Traction battery SOC should be at 50%, and the 12 volt battery should be disconnected or on a trickle charger. Note that this is for long-term storage, not just parking it for a few days or even weeks.

The data I have in here now is what I gathered from reading back a few pages in this thread, including that digested from Charles Whalen's post here last month, WOT's front page article and comments last Thursday, and whatever further comments I can get.

WOT and others, can you help clarify this further? You can just describe the behavior in plain text, and I'll figure out how to fit it in above (adjusting temperature ranges accordingly). It seems like the low temperature operation is what is most unknown here.
 
#122 ·
I am getting more confused. So if i leave my car out on a 100 degree day after depleting the batteries by 50% by getting to work and the inside of the car heats up to 130 degrees what do I do to get the temperature down? Can I even start the car? Can I get the electronics to operate to open the windows or do I just have to open the doors lmao? If I can't start the car to get the combustion engine to run for AC then how am I supposed to cool the car down if I am no where near a plug? Same goes for when it is -20 outside all day. Am I not supposed to drive or let the car sit out during these temperatures for 8 hours? Maybe you are saying I can start the car to run the ICE but I have to wait for the car to cool/heat in order to drive???

Thanks
P
 
#123 ·
So if i leave my car out on a 100 degree day after depleting the batteries by 50% by getting to work and the inside of the car heats up to 130 degrees what do I do to get the temperature down? Can I even start the car?
It's my understanding that the battery is pretty well insulated. I think the way it works is an 8 hour soak isn't enough to bring the battery out of operating temperature range. The battery is probably significantly better insulated than the interior of your car. The car may get really hot as far as you're concerned, not so much for the battery.

Same goes for when it is -20 outside all day. Am I not supposed to drive or let the car sit out during these temperatures for 8 hours?
Same here, but if you're going to leave it out in the cold a *long* time you'd better have a block heater outlet. Just like you would with any other car. An ICE car doesn't do well in that environment either...
 
#126 ·
The car cannot even start without it coming back within range? ChrisC says it's not drivable but doesn't say you can't star the ice. That is a disappointment if you have to somehow get it plugged in, towed, or wait for the outdoor temperature to come back within range. I can't believe if I have 60% battery left and the batteries are close to going over 120 degrees it wouldn't try and cool down instead of creating a scenario where the car cannot be used at all and also allow the batteries to reach damaging temperatures
 
#127 ·
I can't believe if I have 60% battery left and the batteries are close to going over 120 degrees it wouldn't try and cool down instead of creating a scenario where the car cannot be used at all and also allow the batteries to reach damaging temperatures
It's my understanding that if you have 60% SOC the battery CAN'T be out of its temp range. WOT (or anyone else who knows) can comment, but I believe it can always start the ICE hot. It's just a deep cold soak with battery < 50% that forces a plug in. And many places where that can happen have provisions for block heaters.
 
#129 ·
Indeed, therfman, it's recent concerns from folks like you that inspired me to start trying to make sense of this. We'll get to the bottom of it, pun not intended :)
 
#137 · (Edited)
ChrisC.
I like what you are trying to do here, but it wont be easy as putting your finger on some of the actual numbers is quite difficult as they have been somewhat of a moving target of course.But I'll help where I can and for now I can verify a particularly well documented temp of 25F (-4C) as the point where the ICE will be commanded "ON" and the message "ENGINE RUNNING DUE TO TEMPERATURE" appears. (as per Lyle's front page post a few days ago)

Primarily this is to assist the 360V cabin heater in warming the coolant more quickly to insure glass clearing. (remember there is no physical connection between the ICE and battery coolant loops) This engine start will also occur if you used your remote start button or smart phone command to pre-condition the car at colder than 25F. (as documented inthe owners manual)
In either case the ICE will shut off after reaching 150F (65C) (providing you still have sufficient SOC to support all-electric operation) or until ICE temp drops gain.

Of course any "numbers" we document here are subject to change of course, in the event the Volt's calibrations are updated for any reason. Hopefully over the course of the next few weeks though we should be able to create a bit of a guideline as to what to expect based on colder ambients.
My plan was to start a new thread with a reprint of my cooling loop article but havnt got to that as of yet. Perhaps it would be better to just include it a as a post here? Maybe the group can help to decide...

Regards
WopOnTour
 
#131 ·
Page 5-45 of the Operator's Manual says otherwise:

"BATTERY TOO COLD, PLUG IN TO WARM
This message displays during extremely cold temperatures, when the vehicle will not start until the high voltage battery is warm enough. Plug the vehicle in to allow the charging system to warm the high voltage battery, then the vehicle can be started."

I assume that this problem happens because the high-voltage battery is used to start the ICE, and when the battery is too cold, even starting the ICE could damage it. I think it would have made more sense to use the 12V battery to start the ICE, they have been used in the cold for decades to start cars, and they are cheap to replace when they do die from the cold.

Luc
 
#132 · (Edited)
I looked up the all time record temperatures in California to see what the range would be for My Volt.

Record Low - -45F
Record High - +134F

Annual snow fall at Kirkwood Ski resort about 37 miles from my house - 42ft

Some days I just would not be driving my Volt in these areas
 
#134 ·
I'm assuming the Volt doesn't have a 12V starter like a normal car and that one of the two M/Gs actually start the ICE. That would explain why the pack is needed to start the ICE. That said, starting the ICE is much easier on the batteries than driving the car...so it seems like there would almost always be enough power in the batteries to start the ICE. Hmmm..
 
#135 · (Edited)
I've edited the FAQ to point to my post over the weekend about battery temperatures, but I could really use some more information. In particular, I'm most concerned about whether these statements are true:

car won't run until battery is cooled below 122 F by TMS

car won't run until battery is warmed above -13 F by TMS

At extreme temps (high or low), the ICE may come on to generate power for the TMS to work faster, but only if the car is powered on (that is, the ICE won't start by itself, unmanned)
Can anyone say whether they know these to be true? And please note that I'm not saying the Volt won't work below -13F. I am saying that if it sees those extreme battery temps when powered up, it's going to immediately do what it can to warm up the battery before it allows motion. For example, it could be as little as 90 seconds of warmup time, based on Lyle's recent experience.

Please don't report how cold it is in Minnesota right now, we know :)
 
#139 · (Edited)
Shaft
I think you are perhaps making a bit too much of these messages in the owners manul but...
First of all, keep in mind the ICE coolant cannot directly heat the battery as their coolant loops are not common. (as per my article) Generally the battery is heated via the 360V heater. So if ICE was to contribute any heat to the battery it would have do accomplish that through charging operations due to any generation taking place while ICE is running. (and does so anytime the vehicle has stabilized to an ambient of ~25F (-4C) as per my post above)

To the best of my knowledge the scenario where the "BATTERY TOO COLD, PLUG IN TO WARM" message might appear is going to be a very rare occurance when there is some reason why ICE cannot or will not start (low SOC, out-of-fuel or some other problem) AND very cold ambient conditions and then only after a cold soak of many hours has taken place under those conditions.(the insulation of the battery is such that it dramatically slows heat loss from the battery)

I'm trying to get a defined number for battery temps and better clarification when this might actually occur but at this point I know that it is somewhere near or just below -25C (-13F) but in that event the only way to get the vehicle operational is to either plug it in or have the ICE issue rectified/repaired.
HTH
WOT
 
#143 ·
OK, I've merged WOT's latest comments into my post (here).

A few questions about "ambient" temperature:

So if ICE was to contribute any heat to the battery it would have do accomplish that through charging operations due to any generation taking place while ICE is running. (and does so anytime the vehicle has stabilized to an ambient of ~25F (-4C) as per my post above)
You were still talking about the battery pack temperature, right? Not ambient temp outside the vehicle? Just checking.

Is the battery pack temperature measured in multiple locations? If so, are they averaged, or does it trigger on whichever sensor is "worst"? If measured in just one location, I guess that would require that the coolant loop run to equalize the heat.

Can you give me an idea of what kind of timeframe is required to "cold soak" the battery down to ambient? Are we talking 8 hours, or 48?

Thanks!
 
#140 ·
Thanks WOT for the info! I'll merge in as soon as I can, by the end of today for sure.

Another key bit of info, that may be public already but I haven't found it, is what is the low temperature spec on the ICE? Failing that, what is typical for ICE?

I'd rather you kept the discussion here, but that's me. I hate forked threads :)
 
#141 · (Edited)
Thanks WOT.

Follow up: (4 questions)

I realize the ICE cannot heat the battery via its coolant loop. But the ICE can produce electricity for the 360V battery heater, which in my mind beats using a cold battery to heat itself. So, isn't this how it's done if the battery is too cold, not via "charging operations"? (Try that, Leaf!)

You suggest "low SOC" as a reason that the ICE will not start. I do not understand why that might be the case, unless it is so low that MG1 cannot crank the engine. With proper controls, maintenance and storage, I cannot imagine that taking place with such a large battery reserve compared to normal cars. Can you elaborate? And what about boosting?

Is there any situation (e.g. battery temp too high or low and no plug available) where the Volt will ask the driver to wait (i.e. not drive) while the battery is being conditioned by the ICE?

As for making too much of the messages in the Owner's Manual, I suspect that you are right. But until I hear a satisfactory explanation of the exact conditions under which this message is generated by the control system, I'll maintain a degree of skepticism. Can you find out what those conditions are?
 
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