Volt thermal management system temperature band?

[VoltageDrop]

In the Volt, cabin temperatures have almost no effect on battery temps. I'm sure you're thinking of the typical hybrid arrangement where the battery is in the cabin and cooled with a fan the blows cabin air across it, but the Volt isn't like that. The battery lives entirely outside the cabin, underneath the steel body shell (in a cavity in the body between the seats.) There's a small pass through for the MSD, but otherwise there's no connection, and the battery is insulated and liquid cooled.

Remote starts still have value - the TMS runs during them and will use the A/C chiller to cool the battery coolant - but I don't know where you got the idea the engine had to come on - that only happens if the battery is fully drained first.

Really, the point is moot anyway. GM designed the Volt carefully to handle extreme environments, and if the battery is in a SoC and temperature range that risks damage/accelerated aging, the TMS will come on with the car off and use a little bit of battery power to keep it chilled out.

Saghost......I know that the ICE does NOT have to come on during a remote start.....what I meant ( didn't mention it in my previous post but that is the situation I was eluding to) was in the situations where a one way trip depletes the battery or leaves little EV range left thus necessitating the ICE to come on....on the return trip home (not necessarily during the remote start while its parked out in the sun)......

I have read many aposts that elude to the fact that the heat of the cabin (which will be ALOT hotter than the ambient temperature) if sustained long enough WITHOUT being plugged in will have an effect on battery temperature (but this is only after hours where the insulation temperature will at some point start to heat up due to elevated cabin temperatures and thus start transferring some of the heat to the battery).......is it significant if it happens on few occasions to cause permanent degradation of the battery life...I don't know.....if this is a recurrent theme (such as the scenario the OP eluded to)....will likely shorten the battery life......

Again...your last point state that IF the SoC is in a range to support the TMS it will go on and all will be fine and dandy....however... I was eluding to the original post where there complete depletion of the battery in a one way trip (or near completion with Soc below range of TMS support) ....with no ability to plug in and parking out in the hot sun on a hot day......

[2BeLivingGreen]

A lot of good discussion here on the VOLT system and potential work arounds to further protect the battery on hot days.

My question is, does anyone know how slow/fast does the well insulated battery temp rise when parked on a 100 degree day (or other known temp) in an open parking lot? I think if someone had that sort of data or knowledge it would help owners better understand if parking a VOLT with a SOC <75% and not able to be plugged-in has any danger from heat. I would guess that the store run of maybe parking for an hour in 100 degree weather is not going to elevate the battery temp to a harmful level? But I am not sure.

Any of the experts here able to comment?

[mark32]

Sorry for my bad english, I am from germany...
I have noticed that the behavior of the TMS of my Ampera is not the same as it is shown in this post. The active cooling only starts if the HV-temperature rises to 83 F or higher.

With my DashDAQ normally I read the signal 1523 "HV Battery Average Temp" and additionaly signals 1521 and 1522 which have nearly the same behavior. Following the scheme from this guide I interpret the Signal 1607 "ESS Vlv Cmd" as the position of the 3-Way Coolant Flow Control Valve. With this information I can see when the active cooling starts. Most times the signal shows "Bypass" which means Position A in figure. On hot days while driving it shows mostly "Radiator" (= position C) => Only cooling with warm air (from outside) is active. When the HV battery is getting more than 83 or higher it starts with "100% Chiller" (Position B) and active cooling is working.

Is that TMS function different to US-Volts? Is the post confirmed by DashDAQ readings? Maybe I am wrong with the interpretation of the TMS or the DashDAQ...

mark23

[saghost]

Sorry for my bad english, I am from germany...
I have noticed that the behavior of the TMS of my Ampera is not the same as it is shown in this post. The active cooling only starts if the HV-temperature rises to 83 F or higher.

With my DashDAQ normally I read the signal 1523 "HV Battery Average Temp" and additionaly signals 1521 and 1522 which have nearly the same behavior. Following the scheme from this guide I interpret the Signal 1607 "ESS Vlv Cmd" as the position of the 3-Way Coolant Flow Control Valve. With this information I can see when the active cooling starts. Most times the signal shows "Bypass" which means Position A in figure. On hot days while driving it shows mostly "Radiator" (= position C) => Only cooling with warm air (from outside) is active. When the HV battery is getting more than 83 or higher it starts with "100% Chiller" (Position B) and active cooling is working.

Is that TMS function different to US-Volts? Is the post confirmed by DashDAQ readings? Maybe I am wrong with the interpretation of the TMS or the DashDAQ...

mark23

I don't think the function is different. You've dug deeper into the battery TMS behavior than I have to date, but what you're seeing mirrors my impression - on a day with OATs in the low 80s the battery will stay warmer than outside air, while on days in the low 90s the battery will be cooled down into the mid 70s. Since I wasn't reading the Valve command, I hadn't identified a threshold - I was thinking it was slightly higher, but I defer to your more through analysis. Not sure why the data from GM doesn't match the car's behavior exactly.

[mark32]

Actually my ambient temperature is around 72 F. With maximum speed the HV-Temp is not rising above 82 (starts with "Radiator" position C). A volt owner in hot regions (with DashDAQ or similar) may check the HV-Temp in relation to "ESS valve cmd" for confirming the starting point of active cooling the battery (position B Chiller).
I wait for hot days in my city for testing...

[mikeg3]

The owner's manual recommends the Volt car cover. I found the cover very effective in keeping the cabin comfortable when parked in 100+ degree sun. I expect that the battery benefits as well.