[JohnPaul]

Confession: I know very little about how battery systems work, but something I've picked up in the last year or so of getting into EVs is that the actual speed you get at a DC Fast Charger can vary a lot depending on the temperature of your battery.

I assume the Ultium vehicles will be pretty sophisticated about this, like Teslas and other higher-end EVs that precondition their battery packs when you navigate to a fast charger, but one wrinkle that dawned on me specific to the Silverado (and Hummer EV), is whether the size of the pack makes a big difference in the amount of energy required to do this.

Does anyone know about this? Is it fair to say that (for simplicity sake) a 200 kWh pack takes 2x the energy to heat or cool as a 100 kWh pack, or does it not scale like that?

Canadian winters are famously cold and I'm wondering if it will be more difficult to see peak charging speeds on big-battery trucks like these.

 

[ChargedSilvE]

Not sure. I read that Tesla requires you to precondition for 10-20 minutes before Supercharging and hope it isn't any longer here. It would be great for those of us likely to have a fast-charging station close to home, which is something I'm still trying to figure out: Where can I charge my Chevrolet Silverado EV?

 

[Xman]

View attachment 462
Confession: I know very little about how battery systems work, but something I've picked up in the last year or so of getting into EVs is that the actual speed you get at a DC Fast Charger can vary a lot depending on the temperature of your battery.

I assume the Ultium vehicles will be pretty sophisticated about this, like Teslas and other higher-end EVs that precondition their battery packs when you navigate to a fast charger, but one wrinkle that dawned on me specific to the Silverado (and Hummer EV), is whether the size of the pack makes a big difference in the amount of energy required to do this.

Does anyone know about this? Is it fair to say that (for simplicity sake) a 200 kWh pack takes 2x the energy to heat or cool as a 100 kWh pack, or does it not scale like that?

Canadian winters are famously cold and I'm wondering if it will be more difficult to see peak charging speeds on big-battery trucks like these.

As a general rule, the larger the pack the more power it can accept for a given charge level. Yes it takes more power to heat/cool the larger mass, but the larger capacity offsets that. Further, even if a pack is throttled to half of it's potential intake by temperature, a pack twice as large will be throttled to half of that potential; or twice what the smaller pack was taking.

My brother used to have a Tesla with a smaller pack than the one I drive. Un-conditioned supercharging speeds were much lower with his smaller pack than on my larger one.

Moral of the story: Bigger is better... even more so when it is cold. My brother traded his car for one with a larger pack.

 

[bbrriiaann1973]

Do you have to change the coolant? What is the interval??

 

[Xman]

Do you have to change the coolant? What is the interval??

On a Tesla it is the life of the car. I don't know what GM's guidelines are going to be.

 

[bbrriiaann1973]

On a Tesla it is the life of the car. I don't know what GM's guidelines are going to be.

Really, interesting! Is there a fluid level you have to check? I assume.

 

[HawaiiEV]

I don’t trust that “life of the car” BS, ask anyone about their lifetime fill transmission 100k miles later.

 

[bbrriiaann1973]

I don’t trust that “life of the car” BS, ask anyone about their lifetime fill transmission 100k miles later.

I agree with that! I used to work at a service station

 

[Xman]

Really, interesting! Is there a fluid level you have to check? I assume.

The Tesla is a closed system, and they can obviously open it to flush/service it. They do not have an interval listed in the manual.

The Spark EV that I have has a reservoir under the hood much like any other cooling system. The fluid looks like antifreeze and I believe that Chevy does have a flush/changeout interval recommendation, although I do not remember what is is. I would expect the Silverado to have a similar system.

Either way, these systems are pretty straight forward and have been around for a very long time (heat exchange through fluid). Modern medium (the fluids) are very long-lived and in most cases will result in long intervals between services.

While on the topic, I would recommend avoiding systems that are not liquid cooled/warmed, like the Nissan. These batteries are at the mercy of ambient conditions, which can shorten the life of the batteries.

 

[bbrriiaann1973]

Thanks for the info.

 

[wattsup]

On a Tesla it is the life of the car. I don't know what GM's guidelines are going to be.

On my Bolt, it was I believe every 150K miles or... 10 years? whichever came first. At the time Weber Auto was doing their teardown on the Bolt and walked through flushing the battery coolant loop. IIRC it was a long process to drop the battery, flush it, get the air out, etc, I vaguely recall estimates of a grand or two for the service. That said, my old WRX wanted $500 worth of babying every 30K miles, so don't let the sticker shock get you down...

 

[SilverDan]

The Bolt doesn't have any preconditioning AFAIK, unless you leave it plugged in during really cold weather.

For the Silverado a video with the chief engineer it was mentioned that the car will precondition in the morning. The guy asking was from Montana. She said that it will mitigate the range loss you'd see, but sounds like not eliminate it (the battery will still cool down, and/or will suck heat to keep it warm on the road). The Bolt cooled via a bottom mounted cooling plate, that eliminates the need to run fans, even during fast charging, unlike the Tesla. But I've always wondered about cold weather performance and that big cooling plate. Don't know about the cooling architecture with the Ultium though.

Other thing is fast charging temp conditioning. Ideally the new software platform will be smart enough to know where you plan to stop to charge and will precondition. So basically they have the pieces to do this all top-drawer, but we don't know if they will.