DC Fast Charging

Discussion in 'Bolt EV' started by Walter, Mar 16, 2018.

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  1. Walter

    Walter New Member

    I've been reading on this site and others about 150 kW and higher fast charging coming soon to a highway rest stop near you. I know that GM says that the Bolt can take up to 80 kW but was wondering if that means that anything more will fry your Bolt. Are there any Boltsheviks out there who want to weigh in? For instance, if we plug our Bolts into one of these new super fast charger/fryolators, will the Bolt's charge controller be able to automatically step down the charge rate to what it finds acceptable, or will it not allow any charging at all? So far, at best I've seen about 30 kW from an EVgo DC fast charger. Though I enjoy my donut and coffee while waiting, I only get about 75 miles of range added after a half hour.
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  3. WadeTyhon

    WadeTyhon Well-Known Member

    Yep, the Bolt and the DCFC will work together to make sure you do not damage the car. The Bolt will only request as much energy as it can handle! :)

    So far, the max charge rate anyone has seen from the Bolt was about 55-56 kW. There was some lab testing done and there has been one anecdotal report on the Ampera-e hitting about 55 kW on a 70+ kW DCFC.

    From Hybrid Cars:
    "For their initial round of testing on the modified charger, they started a charging session when the Bolt’s battery was 40 percent full and the Bolt then requested 150 amps.

    A lithium-ion battery pack’s voltage naturally rises as it gains charge. When charging at 150 amps, the Bolt’s pack would likely begin charging at a rate of about 50 kilowatts when near empty and then gradually rise until reaching about 55 kilowatts before starting to taper down when the pack reaches just over half full as it does today."

    On a 50 kW charger on a road trip last fall, I was getting in the mid-to-high 40s until I hit a little over 50% State of Charge.

    Most chargers in the US are either 25 kW or 50 kW. But as the vehicle charges, it ramps down the charge rate as your SOC increases. So if you're always charging your bolt with over 55% of your remaining battery, you'll never see the max charge rate. That's the likely reason why you're only seeing a 30 kW rate.
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  4. Walter

    Walter New Member

    That's great info. Thanks for taking the time to provide it. I'm left wondering if Chevy will do some more testing and perhaps increase the charge rate as 150 kW and higher DCFC come on line. It looks like VW is planning its future ID line of BEVs with the very high charge rates in mind.
  5. WadeTyhon

    WadeTyhon Well-Known Member

    Enabling the Bolt to charge at a higher rate would be trivial and a very minimal cost to production.

    However, currently there is no CCS charger in the wild that chargers at a higher rate. And the faster the rate, the more strain is put on the battery pack. Spark EVs and Leafs that are primarily charged by DCFC see faster degradation than those charging primarily at L2 or L1.

    If I had to guess, I'd say the reason they have reduced the charge rate is to prolong the life of the battery. For most people, charging at home is their primary source of charging. So DCFC charging is just an occasional burden when traveling.

    For those who use DCFC on a more regular basis, the slower charge speed and quicker taper down of those speeds will prolong the life of their battery.

    But as the max capacity of EV batteries grow and the battery chemistry improves, we should see those higher charge speeds become the norm, like you suggest. :)
  6. Walter

    Walter New Member

    One of the things, actually, that I've enjoyed on the few road trips we've taken with our Bolt, is that we approach a road trip differently. By this I mean that we take more interesting routes and stop for longer to enjoy a meal near a Level 2 charger that's usually in a town, rather than the usual stuff you find on a turnpike or interchange gas station. So a three hour trip in an EV might take an hour or so longer, but I enjoy the slowed down pace and the scenery. And we're doing almost all our charging at home with Level 2 and solar, giving us a great return on investment. We'll see what the future brings.
    Last edited: Mar 16, 2018
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  8. WadeTyhon

    WadeTyhon Well-Known Member

    Agreed! It is a much more relaxed pace. Taking 20-30 minutes to stretch or legs, grab a coffee, or visit a shop or park or what have you... it reminds me of roadtrips in my childhood.

    I think that's why I had grown to hate road trips. We would always try to get from A to B as fast as possible. So I have generally preferred flying in recent years.

    Maybe we were doing it wrong, because our Austin and San Antonio trips in the Bolt were the most pleasant road trips I'd been on in a while. I guess what's the point of road tripping over flying if you're just gonna blast past everything as quickly as possible lol?
  9. rgmichel

    rgmichel Active Member

    I cannot but agree with the above. I did about 3000 miles of long distance driving in 2017, and I endorse the thought that they were "the most pleasant road trips" I have ever done. The by-ways off the highways were so interesting. New towns, restaurants, shopping encountered while charging were a revelation.
    Robert Bratton likes this.

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