Daniel Fichana's picture

Two Reasons It's a Bad Idea for GM to use Tesla Superchargers

Why GM should stay away from setting up a Tesla-like supercharger network or incorporating Tesla's supercharger network into the Chevy Bolt.
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The Chevy Bolt is a smaller car with presumably a smaller battery. Pumping that current is not a good idea; Tesla gets away with because of battery size. Sure the Bolt could be designed to throttle back the charge, but then you lose some advantage to the quick charge.

Second issue is battery chemistry. Not all lithium batteries are created equal and they. Tesla uses NCA. The Bolt, if the whispers are to be believed, is supposed to use NCM.
From what I've read NCM degrades faster than NCA.

Essentially you have a shorter longevity with NCM and further shortening the longevity by charging it at a higher rate. Will it make a difference in terms of battery longevity, it depends on various factors, but enough of a risk that I wouldn't risk charging at that rate with that chemistry.

The Teslas all have the same battery chemistry. The 60 and the 85 have less risk, since the battery packs are larger; packs lower than that you have to taper back to get the appropriate C so you don't cause as much damage. There are conflicting statements from Tesla, but if you look at Charge rate vs degradation, the faster you charge the faster you degrade the batteries;

When you do that, you will not get the benefits of supercharging and may as well use other standards like CCS or chademo- get no benefit from the SC.

From the degradation curves it appears the number of cycles for NMC to reach 70% capacity is 20% less than that of NCA.

So that's a problem; same reason why Tesla does not retrofit the roadsters to supercharge- the BMS can handle it, but the chemistry inside can not- supercharge LCO a handful of times you'll start seeing degradation.

There's only 2 chemistries that should be recommended for fast charging NCA and lithium titanate; anything else you start getting shaky to some degree.

NCA is not perfect either, but it's one of those that can be solved by engineering and battery management controls at a cost to efficiency.

  • If I was to design a pack without any weight concerns, and has fast charging, lithium titanate hands down
  • If I wanted low weight without any regard to quick charging or degradation- LCO
  • If I wanted quick charging and low degradation (no where near titanate's benchmark though)- NCA
  • If I wanted medium degradation, low cost, moderate charge rates-NCM

If you wanted lowest cost, stable, medium weight, medium/high degradation, no fast charging- LMO or iron phosphates.

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Comments

This article makes no sense, and clearly you don't know enough about batteries to be making any conclusions.

Your headline is pointless too.

Because of the bolt is "rumored" to have this type of chemistry, you conclude using supercharger network would be a bad idea....

First we don't know what kind of chemistry will be used, second superchargers can automatically throttle down to whatever setting the car desires, so you could always supercharge at the max rate your battery can safely handle.

Finally if the degradation is only 20% more like you state than it isn't much of a concern, considering supercharging is not done regularly and model S already has incredibly low degradation like 5-8% for 100k miles, so maybe 8-10% degradation with the other chemistry.

Also you say the Bolt will have a much smaller battery, well if Chevy wants it to go 200 miles like they said, it would need to be at least something like 50Kwh, which would supercharge only a bit slower than a Model S 60.

So you didn't bring up any valid point on why supercharging a Bolt is a bad idea, nor did you do your research before writing this article

Then he didn't proofread it afterwards. I couldn't even get past the first two paragraphs. Gave me a headache.

Wow.... Try learning something before you attempt to teach. You obviously little about batteries or charging systems.

Wow, terribly written. Terribly researched. No facts. No relevant information at all. Please stop writing infotainment articles immediatly.

"Chevy Bolt is a smaller car with presumably a smaller battery." lolwut? The Chevy Bolt should be very comparable to the Model 3; both smaller than the Model S, both with 200+mile range. We've known that since well before you wrote this post...

My concern is less about the chemistry (NCM and NCA can both handle fast charging) but the design of the pack itself. One of the things that limits charge rate is heat. Packs heat up when charging and discharging and one designs cooling systems to remove that heat. If the Bolt has a cheaper cooling system, it might not be able to handle the heat from charging at the fastest rate the cells can take. All that said, the car is in ultimately in charge of the super charger and communicates the desired charge rate. Tesla vehicles already monitor pack temp and might request lower current if the packs heat up too much; a Bolt could as well. Even if that ultimately means taking more time to charge than Tesla vehicles, it would still be faster than charging at 240V AC.