Chargepoint CHAdeMO Quick Charger Power Drops Suddenly?

[MartinChico]

Lately I've been using the Chargepoint Quick Charger at my local Nissan dealer, and I've been monitoring the power and charge rate (via Leaf Spy Pro). I have noticed something that seems odd, but perhaps someone here can explain it.

I noticed that the car initially charges at about 37-38 kW, but then drops down to 27-28 kW after the first 5-10 mins. Effectively, my cost per kWh goes up at that point.



Is this normal, typical? Could this be a problem on the dealer's side?

Thanks.

 

[cwerdna]

Sounds about right. What’s the starting % state of charge (on the car’s display)? What’s it at when you see it taper to that point? Is it actually "sudden" or gradual? I'd imagine it's the latter.

If your starting SoC is high, you might not even reach 30 kW or stay there for very long (e.g. 1 minute).

Have a pic of the DC FC and/or a Plugshare link? (Not that it likely matters.)

 

[MartinChico]

Sounds about right. What’s the starting % state of charge (on the car’s display)? What’s it at when you see it taper to that point? Is it actually "sudden" or gradual? I'd imagine it's the latter.

If your starting SoC is high, you might not even reach 30 kW or stay there for very long (e.g. 1 minute).

Have a pic of the DC FC and/or a Plugshare link? (Not that it likely matters.)

I added a pic to my original listing.

Looks like I'm charging at about 36-38 kW until the car reaches about 65% SOC, then it steadily drops down to 26 kW as the car approaches 75% SOC:



In terms of economics, it makes sense for me to only charge as long as the QC is providing the much higher power; as soon as it drops substantially, I'll disconnect!

Thanks for responding,
Martin

 

[DaveEV]

Looks like I'm charging at about 36-38 kW until the car reaches about 65% SOC, then it steadily drops down to 26 kW as the car approaches 75% SOC:

Yep, that's completely normal.

For the slightly rising part of the curve the charge rate is limited by the maximum amount of current the charging station or car will accept (typically 115-125A or so, though can be significantly lower on some lower power stations), since battery pack voltage is rising the power delivered goes up.

Once the battery pack reaches maximum voltage (~394V / pack, about 4.1V / cell), the car reduces the rate of charging to avoid overcharging the cells.

This is a very typical way to charge batteries - first phase is called constant current, second phase is called constant voltage.

Under constant voltage once the current drops below a certain level, charging stops.

 

[MartinChico]

Look at this charge!

I arrived with about 45-50% SOC, charged for 20 minutes, and left with about 75% SOC. Initially the Chargepoint CHAdeMO was providiing about 36-37 kWh, but this steadily declined to about 16-17 kWh over this 20 minute period. Note that there was no "normal" high power (35-40 kWh) charging at all, really!

 

[knightmb]

It might be the charging station. I live right next to the Nissan HQ where they have rows of free DC quick charge stations. One station can charge the car at +105 amps of power and the one right next to it struggles to hit +60 amps of power when starting a charge from the same battery percentage. So one station can charge the vehicle from 10% SOC to 80% in 22 minutes, and the station right next to it does the same charge to 80% in 35 minutes. So as you can imagine, people tend to avoid that particular charge station unless that is the only one left (I've had that happen, knowing that I am really going to be sitting there for a while waiting for a charge) :shock:

The ones as Nissan anyway charge at +105 amps until about 65% SOC, then tamper off down from there until they are around +45 amps when nearing the 80% charge mark.