Chevy Bolt EV Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
145 Posts
Discussion Starter · #1 · (Edited)
I've read that DCFC has a pretty fast rate when the battery is under 80%.
Please explain the following:

I plugged in at 10:56 PM, battery was 24% full.
337 volt, 51 amp






At 11:56 PM, battery showed 51% capacity, charger station stopped.
349 volt, 51 amp






Questions:

Shouldn't I have gotten at least to 80% battery capacity after 1 hour charging at the displayed voltage and amp?
Why does the Bolt display indicate that I wouldn't get to 80% until 1:16 AM? That's 2 hours later, shouldn't it be 30 minutes?

Thanks,
 

·
Registered
2017 Bolt EV Ioniq 5 reservation
Joined
·
1,719 Posts
Not all DCFC are 40 kW (400 volts x 100 amps). It may be that yours was a 24-25 kW charger, but I am unsure why it was charging at only 17-18 kW. Others will probably have an explanation. Thanks for the post. I’ll learn from the answers as well.
 

·
Registered
Joined
·
293 Posts
If its 24kW nominal, that is at 400V, at 20% lower voltage, the power will be 20% lower, or ~20 kW.

Explanation: its a DOG of a DCFC. There are quite a few of them out there. When picking a DCFC (and we all find our favorites in repeated travel along familiar routes) you need to look at the rated power.

You want nominal power to be 50kW. In 2019 higher values will become available.

Myself, I ALWAYS have the car 'on' when running DCFC initially, so I can see the charging power on the dash. It is sometimes lower than I expect due to various factors....cold, bad DCFC, full moon, etc.

The charging power below 50% SOC should be 42 kW....that will get you 21 kWh in 30 minutes...or about 70 miles of HW range.

You were getting 16 kW (I hate DCFCs that tell you current and voltage without telling you the power...multiply the numbers).

The time to charge on either display is garbage. Ignore it.

The other problem...DCFC's that abort after 1-2 minutes, right after you walk away to get a snack. Happens just infrequently enough that you think it won't do it, always does it when you are in a hurry to get somewhere. Solution: use an app to monitor while away from vehicle.

You might sit with the car during FC a couple times (on a real DCFC) to get a feel for the taper and how long it takes.
 

·
Registered
2017 Bolt EV Ioniq 5 reservation
Joined
·
1,719 Posts
If its 24kW nominal, that is at 400V, at 20% lower voltage, the power will be 20% lower, or ~20 kW.

You might sit with the car during FC a couple times (on a real DCFC) to get a feel for the taper and how long it takes.
Darren: All DCFC taper power as they charge. It is not linear and may be stepwise. The displayed voltage remains the same and the amperage drops. I once started at 100 amps and it clicked off at 5 amps.
 

·
Registered
Joined
·
5,451 Posts
400 volts @ 50 amps is 400x50/1000=20kW. Assuming no losses or tapering. You'll get 20kWh in 1 hour at best. Each bar on the Bolt is 3kWh. So you will get maybe 7 bars in one hour.
 

·
Registered
Joined
·
7,111 Posts
As the other posters have indicated, not all DC Fast Chargers are created equal in terms of their charging speed. That's why it's important to try to find out the charger's power rating when you're looking for one.

The other thing to be aware of is that some EV charging networks limit the duration of the charge. For example EVGo used to limit DC fast charging sessions to 30 minutes, although I believe that they've extended that to 45 minutes now for all their chargers. The Bolt doesn't know about the time limit, though, so it will give you an estimated 80% completion time that may never be reached because the charger shuts off before then.
 

·
Registered
Joined
·
5,451 Posts
Also, if the battery is hot it will not charge at a higher rate. If you've been on a long drive through the hot desert it might need to cool off. You might be able to check if there's any battery conditioning going on. It should try to start cooling the battery once it starts charging. Not sure if that was a factor in this case as charger appears to have stayed at 51 amps. You should have seen an increase in the one hour as the battery cooled.
 
1 - 7 of 7 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top