E-Hybrid Question

[V12Manual]

I run a Porsche Cayenne S E-Hybrid MY16 as my daily. I invariably charge it overnight in the garage using the stock charger.

I have noticed on two or three occasions now that - on re-entering the garage later in the evening to retrieve something from the car - the front electric fan comes on full blow after I relock the car.

This typically seems to happen only if I unlock the car once it is plugged in charge mode and then relock it - then at that moment the fan comes on almost immediately. If I then re-unlock the car, the fan stops. But then it restarts again when I re-lock the car. Unplugging and replugging does not change this behaviour.

It does not appear to happen at all if I dock the charger plug in the car when I arrive home and simply lock the car (and do not re-open it again until morning).

What is going on?
Is this safe?
Will the car burn my house down with a "thermal runway"?

[jkh112]

I suspect the fan is coming on to cool the batteries because they can get hot during charging.
I am not sure why unlocking and locking the car kicks in the fans bit I wouldn't worry as it is normal for them to switch on during a charge.
I should say I have experience of a couple of electric/hybrid cars but no direct experience of a Porsche hybrid.

[V12Manual]

Thanks. That's what I thought.

[anonymous-user]

When you charge your car from an AC source, the car uses its OnBoard Charger (OBC) to rectify the incoming AC voltage to a suitable DC voltage in order to drive the necessary amount of current into the HV battery. That rectification and voltage conversion isn't 100% efficient, and so the OBC is cooled to prevent it overheating. As charging necessarily occurs when the car is stationary, the OBC cooling loop include a fan to positively drive air through the low temperature radiators to remove that heat.

When you plug in your charger, and lock the car, the system carries out a short "pre charge" test, where it checks the safety of the charging connection (isolation and security of Earth) and charges for a short time to ensure the charger works, and can supply the requested current etc. Even if you have set "delayed charging" ie wait for cheap rate tarrif, most systems still do a 5 or 10 sec charge test when the charger is plugged it. That charge test often includes driving the cooling fan to check that it is operational and not blocked, jammed or otherwise failed. Hence, locking your car can immediately turn fans and charge systems.

When you unlock the car, most systems immediately suspend any charging, because they reasonably assume you are about to un-plug the charging lead and drive off. So, unlocking it suspends charging, and hence turns off fans etc. iI you leave the car plugged in, but unlocked, charging is usually re-commenced once the keep alive period has elapsed (typically 3 to 5 min after no further operator commands, ie pushing remote buttons, opening doors etc)