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)?
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*(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.
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.