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Discussion Starter #1
2 questions:

1. Why is the minimum Target Charge Level 40%?

2. If the battery needs both conditioning and charging, do these occur simultaneously or sequentially? If sequential, which occurs first?
 

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1. This is probably best answered by the GM engineers that programmed it, but my guess is that it's because that's about the minimum amount of charge for keeping the battery in an optimal condition. It's also the minimum amount of charge required for it to charge the 12V battery if the car detects that the latter's charge is low while powered off.

2. Simultaneously if needed, but conditioning will occur when the condition is right regardless of charging status.
 

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1. This is probably best answered by the GM engineers that programmed it, but my guess is that it's because that's about the minimum amount of charge for keeping the battery in an optimal condition. It's also the minimum amount of charge required for it to charge the 12V battery if the car detects that the latter's charge is low while powered off.

2. Simultaneously if needed, but conditioning will occur when the condition is right regardless of charging status.
These are very likely. Another potential reason is because discharging lithium batteries to less than 40% can cause as much wear as charging them past 70%. Basically, think of the degradation of a battery as an inverse Bell curve. A lithium battery at 50% to 60% will suffer the least degradation over time.
 

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Discussion Starter #4
I saw a post on Facebook that the battery gets conditioned more if the car is turned on and plugged in than if turned off and plugged in, at least when cooling. Can anyone confirm this? If true, why doesn't the same happen when heating?
 

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I saw a post on Facebook that the battery gets conditioned more if the car is turned on and plugged in than if turned off and plugged in, at least when cooling. Can anyone confirm this? If true, why doesn't the same happen when heating?
You were probably referring to one of my posts, and it is based on my observations. When I turn the car on while charging, battery conditioning almost immediately activates, even when it wasn't doing so previously. I'm not 100% sure why this happens. It could be an intentional design because turning the car on indicates an intention to leave (i.e., you're about to end your charge session). However, it could also be tied to the programming where the Bolt EV doesn't condition the battery as aggressively when it is unplugged and turned off.

Keep in mind, while both AC and DC charging are adding energy to the battery, they operate off of different systems. The Bolt EV will very actively heat and cool the battery when plugged into an AC charger, regardless of whether the car is on or not. With a DC fast charger; however, the Bolt EV might not be using those same parameters. If you are with your car and observing a DC fast charging session (with the car off), many times hearing the fans and pumps turn on aggressively is an indicator that the Bolt EV's charging rate has stepped down. This indicates to me that GM purposely programmed the Bolt EV's battery conditioning parameters around the charging rate step down, which is most likely why it holds off on conditioning the battery until that point (when the car is off).
 

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Discussion Starter #7
I wish that all of these conditioning parameters could be controlled by the user.
 

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I wish that all of these conditioning parameters could be controlled by the user.
Puzzled by that desire. Wouldn't GM electrical Engineering know better about when to cool or heat the battery better than the end user? What would be the benefit of control save a few hundred watts of electricity?
 

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Discussion Starter #9
Puzzled by that desire. Wouldn't GM electrical Engineering know better about when to cool or heat the battery better than the end user? What would be the benefit of control save a few hundred watts of electricity?
Because the engineers are just guessing that range is more important than battery degradation, which it probably is to most drivers. But for those who don't need the range, being able to set conditioning parameters to minimize degradation makes sense to me. I don't think there is any savings of electricity here, just saving the battery from degradation.
 

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Okay some sort of extra conditioning or super conditioning mode that priorities stably battery temp over range. It seems reasonable for GM to make that a software option.
 

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It was actually a post by the moderator, Sean Graham. Do you find that it's true for both heating and cooling?
Sean knows his stuff, and his assertion matches my experiences.

I believe this is only true of cooling. The heating is going to need to take place regardless because plating can occur if the battery cells are too cold. Essentially, the battery won't charge any faster regardless of whether the car is on or off.

In the case of cooling, the conditioning process can unnecessarily steal power from the charging rate (the batteries can always be cooled later). Basically, batteries are okay being a little bit hotter than they'd like for a short period as long as they are cooled down soon after.
 

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You were probably referring to one of my posts, and it is based on my observations. When I turn the car on while charging, battery conditioning almost immediately activates, even when it wasn't doing so previously. I'm not 100% sure why this happens. It could be an intentional design because turning the car on indicates an intention to leave (i.e., you're about to end your charge session). However, it could also be tied to the programming where the Bolt EV doesn't condition the battery as aggressively when it is unplugged and turned off.

Keep in mind, while both AC and DC charging are adding energy to the battery, they operate off of different systems. The Bolt EV will very actively heat and cool the battery when plugged into an AC charger, regardless of whether the car is on or not. With a DC fast charger; however, the Bolt EV might not be using those same parameters. If you are with your car and observing a DC fast charging session (with the car off), many times hearing the fans and pumps turn on aggressively is an indicator that the Bolt EV's charging rate has stepped down. This indicates to me that GM purposely programmed the Bolt EV's battery conditioning parameters around the charging rate step down, which is most likely why it holds off on conditioning the battery until that point (when the car is off).
From my experience, we can control the conditioning of the battery while we use a DCFC. When I charge on a DCFC and have the climate settings on, with the car started, the conditioning occurs (some of the power from the DCFC goes to it). If I close the climate control, the power from the DCFC increases with no valid reason unless the conditioning. This is why I always charge the first leg of a charge with the climate settings OFF and then, after the step down from 45 to 38 kW I activate the climate control.
 

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Because the engineers are just guessing that range is more important than battery degradation, which it probably is to most drivers. But for those who don't need the range, being able to set conditioning parameters to minimize degradation makes sense to me. I don't think there is any savings of electricity here, just saving the battery from degradation.
Be sure that the engineers know very well what they have in hands - lithium ion batteries - and they know very well what impact has on this kind of battery the temperature, the SOC and the aging. This is why the Bolt EV has the charging curve and limitations of the speed of charge. With the new developments in this area, we will see the new GM cars having a better battery chemistry and new and more faster charging curves.
 

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From my experience, we can control the conditioning of the battery while we use a DCFC. When I charge on a DCFC and have the climate settings on, with the car started, the conditioning occurs (some of the power from the DCFC goes to it). If I close the climate control, the power from the DCFC increases with no valid reason unless the conditioning. This is why I always charge the first leg of a charge with the climate settings OFF and then, after the step down from 45 to 38 kW I activate the climate control.
Yes, I've seen that behavior; however, I believe that is simply from latency in the system. Essentially, the charger can just drop 20 A at once. It has to gradually reduce the power output, and the Bolt EV's battery is happy to accept surplus as the charging speed tapers back.
 

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Yes, I've seen that behavior; however, I believe that is simply from latency in the system. Essentially, the charger can just drop 20 A at once. It has to gradually reduce the power output, and the Bolt EV's battery is happy to accept surplus as the charging speed tapers back.
I tested also by enabling and disabling successively the climate control and each time it went from 41-42 (on) to 44-45 (off) pretty much straight forward. Once I pass the first stepdown, there is no longer a difference between the two (on and off climate control).
 

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I tested also by enabling and disabling successively the climate control and each time it went from 41-42 (on) to 44-45 (off) pretty much straight forward. Once I pass the first stepdown, there is no longer a difference between the two (on and off climate control).
Ah, I reread your statement. Yes, the Bolt EV draws excess power from the charger to run battery conditioning and climate control when that power is available; however, when the Bolt EV's charging rate maxes out the power available from the charger, the power drawn by battery conditioning and climate control reduce the charging rate (it recovers if the climate control or conditioning turn off).

What I was referring to was "spiking" the charge rate. What I have observed happen is that when you are running climate control after the first charging rate step down, if you shut off climate control, the battery charging rate will spike for a short period of time before it settles back to the typical max rate. For instance, if my Bolt EV is at 60% battery and charging at 38 kW, I can turn on climate control to max (drawing 42 kW to 45 kW from the charger). If I then turn off climate control, the Bolt EV's battery charging rate will spike to over 40 kW and slowly reduce to 38 kW. Now that I'm thinking of it, I don't recall that happening when running AC. It's primarily been when running the heater, so there might be a difference there too.
 

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I wish that all of these conditioning parameters could be controlled by the user.
Yeah, I live in the Phoenix area and I would trade some range for conditioning when my car sits unplugged at 110+ while I'm at work. Hopefully that heat isn't too hard on my battery, but I know when I have it plugged in at home those temps periodically trigger conditioning. When I'm home and it's hot, I always plug in, even when I don't need to charge.
 

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Yeah, I live in the Phoenix area and I would trade some range for conditioning when my car sits unplugged at 110+ while I'm at work. Hopefully that heat isn't too hard on my battery, but I know when I have it plugged in at home those temps periodically trigger conditioning. When I'm home and it's hot, I always plug in, even when I don't need to charge.
While I would like to see more user control over conditioning, I think GM's parameters outside of en route conditioning are pretty good. I can see why they don't want to give users more control because it would be easy for someone to condition so aggressively (for little benefit) that they leave themselves stranding, which would cause a whole other PR issue for GM.

What I would like to see GM do is a user-controlled "DCFC conditioning" that more aggressively conditions the battery based on outside temperatures. If outside temperatures are higher than the ideal charging speed window (about 75 to 85 F), the conditioning aggressively cools the battery to 75 F. If the outside temperatures are below 60 F, the battery heater aggressively heats the battery to 75 F. Essentially, partial user control, but within set, albeit aggressive, conditioning parameters.
 
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