DC charging, how fast?

[i3atl]

Keep in mind that the CCS unit may have heat issues as well...it's got one huge power supply in it.

Correct, but the same situation applies - cooling issues, as we see on the Signet units, will affect the unit's ability to reach peak power. It will still be able to sustain lower rates, assuming no failed components.

 

[Stevei3]

Hi guys,
it is our observation that the charging rate can vary considerably between chargers, even when they seem to be the same 50kW ABB units. Could be temperature related (like Jim said) or it could be an installation thing. Not enough grid power or something ?
Regards, Steven

PS: interesting observation on the side: the 50kW ABB chargers at BMW i-agents (we use them regularly in the Netherlands, Germany and Switzerland) tend to charge the fastest and seem to keep charging at a high rate for longer.

 

[i3atl]

Hi guys,
it is our observation that the charging rate can vary considerably between chargers, even when they seem to be the same 50kW ABB units. Could be temperature related (like Jim said) or it could be an installation thing. Not enough grid power or something ?
Regards, Steven

PS: interesting observation on the side: the 50kW ABB chargers at BMW i-agents (we use them regularly in the Netherlands, Germany and Switzerland) tend to charge the fastest and seem to keep charging at a high rate for longer.

In our testing, the reduced rates have always been the result of one or more of the following:

Temperature
Input power
Failed modules inside the unit

Unfortunately we don't have the ABB units here locally - I wish we did, as they seem to be of similar quality to Efacec units, which are quite reliable and consistent regarding output.

 

[davidzi3]

I can't seem to get much more than 20kW speed out of the EVgo or the BMW ChargeNow systems in South Florida. Anyone else having the same issue? The chargers seem to be rated for 50kW, but I never get that speed. I wonder if EVgo is throttling it down for the free 30 min sessions or if its my car? Initially DC Fast charge wouldn't work with my car and BMW had it for over a week to get it working. I wonder if it had issue going to 50kW so they programmed it to only accept less. Am I a crazy conspiracy theorist?

 

[i3atl]

I can't seem to get much more than 20kW speed out of the EVgo or the BMW ChargeNow systems in South Florida. Anyone else having the same issue? The chargers seem to be rated for 50kW, but I never get that speed. I wonder if EVgo is throttling it down for the free 30 min sessions or if its my car? Initially DC Fast charge wouldn't work with my car and BMW had it for over a week to get it working. I wonder if it had issue going to 50kW so they programmed it to only accept less. Am I a crazy conspiracy theorist?

20kW at what SoC? How are you determining the charge rate?

What specific (ABB/Efacec/BTC/etc) charging station are you using? The small, blue BMW DCFC boxes are only 24kW units. As noted above, if your battery is hot or cold, or if the DCFC unit is in need of repair, you may see lower charging rates.

 

[davidzi3]

I can't seem to get much more than 20kW speed out of the EVgo or the BMW ChargeNow systems in South Florida. Anyone else having the same issue? The chargers seem to be rated for 50kW, but I never get that speed. I wonder if EVgo is throttling it down for the free 30 min sessions or if its my car? Initially DC Fast charge wouldn't work with my car and BMW had it for over a week to get it working. I wonder if it had issue going to 50kW so they programmed it to only accept less. Am I a crazy conspiracy theorist?

20kW at what SoC? How are you determining the charge rate?

What specific (ABB/Efacec/BTC/etc) charging station are you using? The small, blue BMW DCFC boxes are only 24kW units. As noted above, if your battery is hot or cold, or if the DCFC unit is in need of repair, you may see lower charging rates.

That makes sense, the BMW DCFC gave me about 23kW from a dead battery. I used the chargepoint app to check the charge rate (it started to taper off at 80%). The EVGgo I typically use indicates 50kW on the charger, but I get 10kW in 30 minutes every time i go. I dont charge at the DCFC at anything over 50% because they are all at least 40 miles from my house. Sometimes I go straight from the highway (hot battery?) and others, like this past weekend, I stopped first and went after a short 2 mile drive (cold battery?)

 

[i3atl]

That makes sense, the BMW DCFC gave me about 23kW from a dead battery. I used the chargepoint app to check the charge rate (it started to taper off at 80%). The EVGgo I typically use indicates 50kW on the charger, but I get 10kW in 30 minutes every time i go. I dont charge at the DCFC at anything over 50% because they are all at least 40 miles from my house. Sometimes I go straight from the highway (hot battery?) and others, like this past weekend, I stopped first and went after a short 2 mile drive (cold battery?)

I doubt that it's cold enough in south Florida to cause any reduction in charging speed.

Even when I've done several back to back DCFC sessions after long highway trips, I don't think I've seen charge rates as low as 20kW at low SoC. 50kW units that only provide 38-40kW are very common, so maybe you're seeing a starting charge rate in that range, then combined with the taper you're getting down to a 20kW average.

 

[jadnashuanh]

A hot battery can cause things to limit the charging rate as well as an excessively cold one. The act of charging will warm the battery, so at some point, it can, if it started out quite cold, peak out depending on the original SOC. Note, many of the CCS units also have a fall-back charging rate based by its own temperature. So, if someone just before you was peaking things out, it might be hot enough (normally, probably only if it is really hot out or the filters for it's air cooling are clogged) to cause it to limit its output level. Many of them also utilize multiple, parallel units, and can continue to work if one of them fails, but limits its output capability.

 

[i3i8]

Just to spell this out, for 2014 i3 models, the first 30 minute of charging will get an i3 up to around 80% regardless if you have the standard Level 2 or the upgraded DCFC?

 

[jadnashuanh]

Don't take this as gospel, but, since the DC charging bypasses the on-board ac-dc conversion process, I'd guess you'd get the same performance on a CCS charge, regardless of the on-board ac charging capacity. I don't think I've ever seen that stated either in the manual or on a forum, though.

 

[cdnji]

Just to spell this out, for 2014 i3 models, the first 30 minute of charging will get an i3 up to around 80% regardless if you have the standard Level 2 or the upgraded DCFC?

What is the rating for a "standard" L2 charger? I ask because it seems like I should have done a better job selecting a L2 charger considering I went to the trouble of getting a new 40A circuit installed.

I have a 2017 REx and have a ChargePoint L2 charger at home. One thing the charger does is keep track of how much energy/power it is sending to the i3. My longest charging session went as follows:

• Duration = 10min | Power = 7.3kW | Energy(total) = 1.22kWh
• 35m | 7.3kW | 4.23kWh
• 1h | 7.4kW | 7.29kWh
• 1h 25m | 7.4kW | 10.37kWh
• 1h 50m | 7.4kW | 13.46kWh
• 2h 15m | 7.4kW | 16.55kWh
• 2h 40m | 5.1kW | 19.42kWh
• 3h 5m | 1kW | 20.51kWh

So 35min into the charging session, the total energy dispensed by the charger was 4.23kWh. Assuming that the 2014 i3 and 2017 i3 charging rates are the same - the 2014 13 would also draw 4.23kWh in 35m - then the 4.23kWh represents a 22% incremental charge for a 2014 i3.

 

[jadnashuanh]

There's a huge difference between DC fast and AC charging, at any level. In the DC charging scheme, high voltage DC voltage is fed nearly directly into the batteries, bypassing the internal ac-dc converter. The maximum the current i3 can handle on this path is 50kw/hr but note that not all CCS units can provide that level, just like with EVSE's, they aren't all created to be able to provide excessive power - mostly to save money. So, you can get a fairly decent charge in a fairly short time. AC charging (whether level 1 or level 2) is dependent on the i3's internal power supply. Depending on the market and options (and maybe the model year), the i3 could provide somewhere between 3.7 - 7.4Kw/hr (possibly a bit more in some countries) input, assuming the EVSE was designed to provide that amount. Some of the newest i3's, sold outside of the US, have a larger on-board ac-dc power supply available. In the USA, with a 40A supply, the largest EVSE you can utilize based on our electrical code is a 32A unit (80% rule applies from the code). Even if you have a larger unit with appropriate wiring, currently, the i3 cannot utilize more than that 32A based on the size of its internal ac-dc power supplies. At some point, those could be made bigger, so a larger EVSE might then let you charge faster, but it will still work fine, just slower even if the supplies get larger in future cars.

Now, how fast the car will actually accept power is dependent on numerous factors which include the size of the EVSE, the battery's temperature, the starting state of charge and the current level of charge. Note, your actual supply's voltage level will affect the charging rate. Since power=volts*amps, if the voltage is lower, even at the same amount of amps, the power delivered will be lower. Say you have a 32A EVSE and your input voltage is 208 (a common commercial power level in the USA), 208*32=6656W, while the same unit in your home might have 240*32=7680W available (the i3 would not draw the full 32A in this situation since it's power supply is limited internally to 7400W). Having more available wont' hurt, the car just won't use it. Just like a 75W light bulb works just fine on a 15A circuit...it takes what it needs.

 

[alohart]

What is the rating for a "standard" L2 charger? I ask because it seems like I should have done a better job selecting a L2 charger considering I went to the trouble of getting a new 40A circuit installed.

There is no "standard" L2 electric vehicle supply equipment (EVSE - the charger is in the car, not in the device that you install). L2 chargers run at voltages that can vary from 208V to 240V. Various L2 chargers are available with maximum currents between 16A and 60A.

The L2 EVSE that you have charges your i3 at its maximum rate, ~30A, so your EVSE choice was ideal for your i3 and for almost all current EV's.

 

[tech]

I'm going to bump this thread since I've been looking into the performance of various DCFC options at interstate charging in the US Southeast.

It appears that ChargePoint has the fastest chargers like the CPE-200. These appear to offer the i3 rates that are close to the 50kW peak rate. ABB also performs well with the Terra 53. Most BTC systems (EVP-FC-50) say they'll deliver 50kW, but actually top out at about 40kW.

Assuming you can drive in EcoPro and get about 4mi/kWh, that means on a long trip you'll likely get 25kWh from the ABB DCFC after a 30 min stop (close to 100 miles) but only 20kWh from an BTC station (closer to 80 miles). This is near the full usable capacity of the battery, so it make the math work out nice for a comparison.

Anyone here had the chance to graph charging curves at different brands of DCFC for comparison? If I could figure out how to share an image, I'd include one for my Chargepoint session near Cartersville GA.

--Calvin

 

[bwilson4web]

When I used the Electrify America, fastDC charger, the highest rate was ~43 kW but there was actually some variability. It tapered down as expected but I never saw 50 kW. The station is rated at 350 kW.

The local Huntsville fast DC charger is rated at 40 kW, 100 A maximum, and works very nicely at that rate. The EVgo station in Nashville also never went over 40 kW, 100 A limited.

Has anyone seen 125 A charge from a fast DC charger?

Thanks,
Bob Wilson