Different charging rate on PMCC and Taycan display

[origjedimaster]

So I had a problem with my onboard charger (see a previous thread - resolved.) Now that I got the car back, I’ve been paying close attention to the charging performance.

Yesterday when I charged it, I noticed the charge rate was displayed differently between the PMCC and the car. The PMCC was showing 9.34 kw (just about right) but the car was showing 8.39 (Not right)

i waited for the car to finish charging and based on the time it took, the PMCC was correct.

Has anyone seen this before?

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[raharris]

Yes, i seem the same thing, but haven’t stressed about it. Only recently have an upgraded circuit in the garage, so I’m just happy the number is now bigger than 1

 

[AndiL]

Both are correct, as they measure the power at different points. The PMCC inside the device and the car probably much closer to the battery.

As the On-Board-Charger and all other devices required to run charging also consume power and need to convert from AC 120V (in US) to DC 800V, you will rarely see close the numbers in this scenario. The OBC alone can draw 500W to 1kW power from what I heard.

 

[daveo4EV]

the value on the PMCC is the amount of “raw” power being delivered to the vehicle
the value inside the vehicle is the amount of power being added to the battery

the difference is a combination of AC/DC charging losses due to conversion overhead (the PMCC delivers AC power to the onboard charger inside the Taycan - it converts AC power to DC power since all batteries are DC power - there is always some % loss in this type of conversion it’s unavoidable) - and any parasitic losses due to running equipment inside the vehicle during the charging process.

my PMCC delivers about 9.6 kW “raw” power, but I see 8.86 kW inside the vehicle that represents the actual amount of power being added the battery - this is common and expected.

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