Does Porsche limit available power?

[Gwaihir]

Hi Forum,
Having my GTS for almost a year and almost never let the state of charge go below 50%, I decided it was time to get a deeper discharge of the battery. Reason? I had read somewhere (not sure of the source) that the only time the pack does a complete cell balance is from below 20% state of charge, so I decided to give it the chance.The surprise for me was giving the car a bit of a squirt with the SOC around 20% resulted in quite a noticeable reduction in power! Ok, still plenty remaining, but still very noticeable. I fully understand that as the cell capacity is reduced the voltage will also reduce, resulting a lower pack voltage and a reduction in maximum available power, but I would have expected Porsche to design the system to give you your full power over most of the battery capacity!

I don’t remember ever seeing a specification saying “you have reduced power as the battery charge reduces.” So I’m asking the question “Has anybody else seen this condition, or is it just me?”

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[DerekS]

My first Taycan test drive was at a low SoC below 20%, and it felt quite anemic.

So much so I requested another followup test drive at a higher SoC before I committed to buying.

I don't have hard evidence but to me it feels like power is reduced when in the yellow/red.

 

[f1eng]

I definitely get worse performance when the battery is cold, but that is what I would expect. I haven’t done enough driving at less than 50% charge to have a valid experience.

 

[SHN]

Yes, you get less power, when the SoC is low. I don’t remember If it’s 20%, but I have had mine on the ring several times, and can confirm the behavier.

 

[ShiftyWolf]

Only experience with this was test driving a Q4. It did reduce power due to a low battery charge.

 

[Rik_CT4s]

Power is often reduced in cold weather and at certain SOC.
I have seen even reduced power at around 50% SOC with low outside temp (few degrees at most). It decreases power even more when you combine cold battery temp with low SOC.

In summer this is generally below 30% SOC (as battery temp is generally fine during this season), in Winter I see power cuts at different battery temp and SOC. Not very predictable, but anything above 60% gives you full power regardless battery temp (i drive a TS CT).

 

[WuffvonTrips]

It does seem to be a common observation when YouTubers are timing acceleration when EVs are at low SoC (even at 50% in one instance, IIRC and assuming the analysis was correct).

 

[Zcd1]

Every EV loses power to some degree as SOC drops.
Some mask the power drop better than others, but physics dictates that power will eventually drop as the battery voltage drops.

 

[Avantgarde]

There is some power drop at low soc due all due to voltage fluctuations. The battery voltage can fluctuate between 610 and 834 volts for the larger battery depending on temperature and soc. Some of the drop can be compensated with higher current but i believe you don’t get full offset at very low soc.

As far as i know all EVs suffer from this problem and it is more evident in Teslas. The main reason Taycan has a different “launch control overboost” power is also because of this issue. So that porsche can publish a higher peak power that could be consistently produced when launch control is active (LC does not work when battery voltage is below certain level).

My speculation is the published peak power for non-LC is the power you get in worst case scenario (eg low SoC) - so porsche technically not underdelivering. When SoC is higher you get something higher than the official non-LC figure but still less than official LC power. Per my butt dyno The power difference between LC and Non LC(but high SoC) power does not feel as big as implied by the difference in official figures but more like represents the worst case (low soc/cold battery) and best (when LC is enabled).

 

[AGDunc]

I've only ever noticed the <20% power reduction, and then the difference is very noticeable. I'd compare it to changing from Normal to Sports Plus, but in the opposite direction to Normal, if that makes sense.

I've not seen any reduction in power due to low temperatures (and its been dipping to freezing in the UK in the last couple of weeks), but my range has seen a 10-15% hit

 

[Gwaihir]

Every EV loses power to some degree as SOC drops.
Some mask the power drop better than others, but physics dictates that power will eventually drop as the battery voltage drops.

I’m not so sure. There is no reason why the Taycan couldn’t be designed to give its maximum power at its minimum battery voltage. Let’s be honest, 650V plus is way higher than Tesla’s 400V system and we know the power they can generate.

 

[Därk]

I think it becomes noticable at around 20 % in cold weather.

 

[bsclywilly]

Every EV loses power to some degree as SOC drops.
Some mask the power drop better than others, but physics dictates that power will eventually drop as the battery voltage drops.

My 4 maintains power very deep into the battery. I think the lowest I've ran it on track is down to about 5% with zero loss (see pic below). But that's mainly because the power is already capped, while using the same components as other models.

It hasn't been pointed out yet, but the reason low SOC could result in power loss is because as the voltage drops, current needs to be increased to maintain the same power. Running higher currents is the main contributor to heat generation in the battery, invertor, and everything else in the power electronics. It could be that the higher output Taycan models actually have a cap in max current output.

A different issue is low temperature, which limits the available current the batteries can output. But the rest of the electronics are not limited in low temps.

Here's an example of how voltage drops and current increases to maintain the same power: (look at the peak values)

SOC from 95%-50%

SOC: 50%-10%

 

[Gwaihir]

My 4 maintains power very deep into the battery. I think the lowest I've ran it on track is down to about 5% with zero loss (see pic below). But that's mainly because the power is already capped, while using the same components as other models.

It hasn't been pointed out yet, but the reason low SOC could result in power loss is because as the voltage drops, current needs to be increased to maintain the same power. Running higher currents is the main contributor to heat generation in the battery, invertor, and everything else in the power electronics. It could be that the higher output Taycan models actually have a cap in max current output.

A different issue is low temperature, which limits the available current the batteries can output. But the rest of the electronics are not limited in low temps.

Here's an example of how voltage drops and current increases to maintain the same power: (look at the peak values)

SOC from 95%-50%

SOC: 50%-10%

What you are showing is what I expected to be how the power is maintained. Maybe the GTS is closer to the upper limit and not able to provide the BHP as the voltage reduces. If that’s the case, Porsche should have mentioned it in the specifications.

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