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 Post subject: Problem Obtaining Full 6.6 kW (20 miles/hr.) at ChargePoint
PostPosted: Sat May 06, 2017 8:04 am 
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Joined: Sun Apr 02, 2017 10:30 am
Posts: 7
Hi, fellow Bs. I am a new B-class owner and am encountering a charging issue while using a ChargePoint station in my area. It is a Level 2 station offering 6.6 kW (J1772), which should equate to 20 mi/hr.

My charge speed is set at "Maximum." The weird thing is that when I use a ChargePoint charger, I'm receiving only a trickle of kWs. For example, just yesterday, it took almost 6 hours to achieve a mere 15 kWh of added energy. At the same station approximately a week earlier, it took nearly 10 hours to gain 25.76 kWh.

By way of comparison, when I charge at the MB dealership, which offers 3 Phase Keba charger, I encounter no issues and am able to fully charge within a few hours or so.

When I called ChargePoint (now several times) about the issue, I was told that it depended on my vehicle's ability to take in the power offered. When i noted that my vehicles charger is more than adequate at 10 kW and my battery capacity is 28 kW, the ChargePoint representative merely noted that, based on their records, some EV owners are able to charge at a full 6.6 kW.

Please help! What am I doing wrong?

Thank you for any guidance you may be able to offer.


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 Post subject: Re: Problem Obtaining Full 6.6 kW (20 miles/hr.) at ChargePo
PostPosted: Sat May 06, 2017 2:54 pm 
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Joined: Thu Dec 11, 2014 9:12 am
Posts: 487
Dunno. I use CP regularly at my parking lot and it puts out 6.6Kwh and I fill up in roughly 4 hours. Wave the fob, plug in and thats it. CP has the data as I see it on their app. Sounds like something is wrong with their charger if you don't see this problem anywhere else.

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Jeff in NYC
MB '14 B Electric; MB '06 E500W; MB '81 380SL


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 Post subject: Re: Problem Obtaining Full 6.6 kW (20 miles/hr.) at ChargePo
PostPosted: Tue May 16, 2017 7:44 am 
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Joined: Mon Jan 05, 2015 3:08 pm
Posts: 96
I don't have the exact specs handy but there are many factors that can effect the charge rate and miles added per hour. In no particular order.....

208v (typical commercial power) vs 220v-240v (typical residential power)
Most ChargePoint, EVgo, you name the public charger is most likely going to be fed from a 208v commercial power source. A 40A breaker allows 32A (some are even further limited to 30A) of charge current, but there is more Kw in the 220/240 configuration at home (~7.2-7.7kW) vs. the 208v (~6.6Kw) in a commercial location.

Then you have the loss factor of the charger itself (in the car), some of the power (~10%) pulled from the EVSE / wall is lost in the conversion to DC in the car to charge the battery.

There are some dual public chargers, if a second car connects to the other side of the charger you are on your charge rate can be reduced depending on the station and how it is configured. Meaning some dual public chargers can't supply full power to 2 cars at once.

I'll add one more variable, lower the SOC of the battery the faster it charges. If you connect at 20% SOC vs. 80% SOC there is a significant difference in the number of miles added per hour of charging. As the SOC rises in the battery it slows down. There is a lot of discussion about this with Chevy Bolt owners using the DC fast charge, if the SOC isn't low enough it doesn't utilize the full 50Kw, it ramps down big time as the SOC gets above 50% and 80%.


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