[raitchison]

So the other day I got in my car and the battery was the hottest I've ever seen, the battery was 95F/35C with outside air temp at 104F/40C.

Battery charge was good at just under 80% but I saw no evidence that the car was or had performed any battery conditioning prior to me pressing the power button on the dashboard.

Predictably as soon as I did press the button cool air started coming out of the vents and I knew battery conditioning had started.

As I made my drive home the battery temp dropped pretty rapidly to 91F/33C in about 17 minutes before battery conditioning ceased.

One thing I noticed looking at the data that the main "Battery Temp" PID reached 91F/33C in just about 10 minutes but the battery conditioning did not stop for another ~6 minutes. The cessation of battery conditioning (as measured by non-zero "battery cooling pump" RPM) doesn't seem to match up perfectly to anything but is very close to a change in temp to ~88F/31C for "*BECM Battery Section 1 Temp" which leads me to suspect this is the temp sensor that governs when battery conditioning occurs. FWIW this was ~93F/34C before I started the car. I'm going to add this PID to my Torque display so I can watch it in real time.

I waited a couple minutes to make sure that battery conditioning was indeed done and warm air was blowing out of the vents before I turned on the AC. The cold air resumed and the "battery cooling pump" started spinning again but the main battery temp PID did not change at all in the rest of my drive home. The only battery temp PID that dropped at all during this period was "*Batt Temp 2417" PID which dropped by 1C.

This is interesting because it sure does indicated that while battery conditioning does also cool the passenger compartment it seems that air conditioning doesn't contribute in any meaningful way to cooling the battery.

Also when I ran some really quick and ugly graphs I noticed some interesting things about the "*Batt Coolant Pump RPM" PID:
1. When running battery conditioning this pump would turn itself off and on periodically, usually only off for a brief period before spinning up again..
2. The RPM of this pump seems to pulse, but it maintained 6500RPM (which seems to be it's maximum) for a fairly consistent period of time before is started to vary/pulse after I first turned the car on (during the battery conditioning period).
3. When I was running air conditioning this pump spiked briefly to 6500RPM before it dropped and settled out at a fairly consistent 2000-2500 RPM. You don't see the pulsing and on/off cycles like you do during battery conditioning and overall the RPM is much lower. (battery conditioning seems to spend most of it's time between 3000-5000 RPM)

In any case here is the torque log for anyone who wants to dive deeper than I have https://www.dropbox.com/s/l6la5nm6wp7c0w4/trackLog-2018-Jul-16_17-48-50.csv?dl=0

 

[raitchison]

Hrm I just looked at the "*BECM Battery Coolant Temp" PID and noticed that it pretty quickly dropped into the mid 60s during the battery conditioning portion but rose steadily after that getting back up to about 96 (just over ambient). This all but confirms that air conditioning does not cool the battery, apparently at all.

Also it seems to confirm that the "Battery Cooling Pump" PID isn't really related to battery cooling as much as the air conditioning system, which is also used to cool the battery. Could this be the fan mounted on the AC condenser coils and not a pump at all?

 

[Fivedoor]

Hrm I just looked at the "*BECM Battery Coolant Temp" PID and noticed that it pretty quickly dropped into the mid 60s during the battery conditioning portion but rose steadily after that getting back up to about 96 (just over ambient). This all but confirms that air conditioning does not cool the battery, apparently at all.

Also it seems to confirm that the "Battery Cooling Pump" PID isn't really related to battery cooling as much as the air conditioning system, which is also used to cool the battery. Could this be the fan mounted on the AC condenser coils and not a pump at all?

It could be the AC compressor itself, unless you have a different PID for the compressor?

Later,

Keith

 

[Chwkev]

I find this kind of data interesting, but I don’t understand where it comes from. How do you track this info? What does the acronym PID stNd for?

 

[raitchison]

I find this kind of data interesting, but I don’t understand where it comes from. How do you track this info? What does the acronym PID stNd for?

I'm no expert on this stuff but Google tells me that PID stands for "Parameter ID", more info: https://en.wikipedia.org/wiki/OBD-II_PIDs

As for how to capture this data yourself this is the best info (and what I used): https://www.chevybolt.org/forum/10-technical-discussion/26666-chevrolet-bolt-obd2-pids.html

 

[raitchison]

It could be the AC compressor itself, unless you have a different PID for the compressor?

The more I think about it the more I think it is the cooling fan. I noticed when I got home and I was battery conditioning at the time so I left the car "on" and when I got out of the car the cooling fan was VERY loud, I've been outside my car several times when just the AC was running and you could hear the fan but it wasn't that loud.

Clearly there is some sort of pump (or more than 1) that circulates the coolant through the battery (and other components that get cooled) but I don't know if it can be measured by OBD or what the PID is if it can.

 

[GregBrew]

This seems to support the observation that the vehicle does *not* condition the batteries unless the vehicle is plugged in, or "on".

 

[raitchison]

This seems to support the observation that the vehicle does *not* condition the batteries unless the vehicle is plugged in, or "on".

It might, but it might only do so at a much higher temperature that I haven't seen yet, but so far it seems it doesn't.

 

[GregBrew]

It might, but it might only do so at a much higher temperature that I haven't seen yet, but so far it seems it doesn't.

True. Perhaps because it's not shore power, the trigger is at a higher temperature. I'd hope that this wasn't the case, in the interest of protecting a very pricey battery pack at the expense of a couple of miles of range. I'd prefer the trade-off to protect the battery.

 

[XJ12]

@Pete Blair has seen his Bolt report conditioning while sitting for nine hours in the hot sun. It is from either a higher set point as @raitchison mentions or maybe the car only checks the battery after so many hours. Would think the car doesn't continuously check the battery while being off. Unless the car has a temperature switch. A switch is a mechanical device that normally has a higher set point so it isn't constantly being cycled. It is more of a backup. Had worked on spacecraft in a former life where there was a primary temperature sensor but a temperature switch of a bimetallic type in case there was a malfunction in the primary sensor.

 

[GJETSON]

Clearly there is some sort of pump (or more than 1) that circulates the coolant through the battery (and other components that get cooled) but I don't know if it can be measured by OBD or what the PID is if it can.

There are three identical pumps...one for each coolant loop. They aren't more than a couple hundred watts, and I don't imagine they have a variable speed controller for these simple pumps.

Pop the hood. At the left front you will see the coolant reservoir for the traction battery loop. If you run your hand down under the reservoir, you will find the hose going down to the coolant pump. There is only one pump, about the size of my fist. It is 12 volts, fuse 55 under the hood. I don't recall the exact fuse size, and the wife is off with the car again.

 

[Chwkev]

As for how to capture this data yourself this is the best info (and what I used): https://www.chevybolt.org/forum/10-technical-discussion/26666-chevrolet-bolt-obd2-pids.html

Thanks!

 

[GlenandhisBolt1!]

I suspect battery conditioning may occur even when the vehicle is 'off' and unplugged, but I haven't observed it. I suspect there is a separate fluid (and control) circuit for air conditioning and battery conditioning, connected by valves to the same air conditioning system that transfers heat from the liquid coolant to the outside world.

 

[GJETSON]

In any case here is the torque log for anyone who wants to dive deeper than I have https://www.dropbox.com/s/l6la5nm6wp7c0w4/trackLog-2018-Jul-16_17-48-50.csv?dl=0

I didn't set up all the PIDs on my tablet, because doing stuff on a little touch screen is a particularly nasty form of torture. However, I see you have set up what appears to be DC-DC voltage, and accessory/12 volt battery voltage as two columns on the right. That would be very useful info. Can you tell me which PIDs those are? Are they some of the ones labeled MG Voltage?

 

[raitchison]

I didn't set up all the PIDs on my tablet, because doing stuff on a little touch screen is a particularly nasty form of torture. However, I see you have set up what appears to be DC-DC voltage, and accessory/12 volt battery voltage as two columns on the right. That would be very useful info. Can you tell me which PIDs those are? Are they some of the ones labeled MG Voltage?

I started with the advice from the PID spreadsheet, with all the "!" PIDs and then started adding interesting looking ones from there.

12V I keep an eye on because I don't know how much power my (very old) OBDII adapter pulls, I leave it plugged in nearly all the time too.

I'm pretty sure the 12V PIDs I'm using are PIDs built into Torque, look at "Voltage (Control Module)" or "Voltage (OBD Adapter)". I log both of those, and they are near the bottom of the list.

 

[raitchison]

True. Perhaps because it's not shore power, the trigger is at a higher temperature. I'd hope that this wasn't the case, in the interest of protecting a very pricey battery pack at the expense of a couple of miles of range. I'd prefer the trade-off to protect the battery.

I agree, I would expect that there would be some sort of logic where as long as the traction battery was above a certain SoC (say 40%) the car would/should feel free to run battery conditioning regardless of if the car was "plugged in" or not.

 

[raitchison]

@Pete Blair has seen his Bolt report conditioning while sitting for nine hours in the hot sun. It is from either a higher set point as @raitchison mentions or maybe the car only checks the battery after so many hours.

When I was on vacation for the past couple weeks it apparently got up to 117F at my house, so there is a good chance the battery would have conditioned but I know it didn't because I put the car in long-term storage mode with the 12V battery disconnected. No telling how hot my battery actually got because battery temp never gets as high as the high temperature for the day but it's safe to assume the battery got well over 40C. Now it wasn't being "used" (discharging or charging) at this temperature but still I'm sure the battery didn't like it.

I knew it would be hot but I only thought it would get into the mid 100s at most. If I had known the temps would get as high as they did I probably would have made the decision to plug in to L2 instead of disconnecting the 12V battery and take the hit from maintaining a ~90% SoC for 2+ weeks to keep the battery cool.

 

[GJETSON]

I'm pretty sure the 12V PIDs I'm using are PIDs built into Torque, look at "Voltage (Control Module)" or "Voltage (OBD Adapter)". I log both of those, and they are near the bottom of the list.

Hmmm. I think I may have deleted the standard PIDs that came with Torque Pro, thinking I would have no use for them. :-(

How do you access them?

 

[raitchison]

Hmmm. I think I may have deleted the standard PIDs that came with Torque Pro, thinking I would have no use for them. :-(

How do you access them?

When I'm in the "Select what to log" interface I scroll all the way to the bottom of the list of available PIDs, these are the 2nd and 3rd from the bottom.

I didn't even think you could delete the built-in PIDs, I don't see where you can.

 

[GJETSON]

When I'm in the "Select what to log" interface I scroll all the way to the bottom of the list of available PIDs, these are the 2nd and 3rd from the bottom.

I didn't even think you could delete the built-in PIDs, I don't see where you can.

When I go to "Select What to Log" I see all the Bolt PIDs that I had selected, plus two more. Those last two are...Kilometers Per Litre, and Litres Per 100 Kilometers.

Believe me. If there is any way to screw up computer software, I will find it.