BMS SOH (84%) vs. Independent AVILOO Flash (91%)

[Swissdude]

Hi everyone,

I’m in the final stages of purchasing a 2021 Taycan 4S Cross Turismo (32,000 km) in Neptune Blue. The Porsche dealership provided an independent AVILOO Flash report as part of the sales documentation, but the results have raised some questions I’m hoping you can help with.

The Data:

• AVILOO Flash SoH: 91% * AVILOO Benchmark: "Below Average" (ATTACHED BELOW The report explicitly flags the battery health as lower than the median for similar age/mileage Taycans).
• Porsche BMS SoH: 84% (provided by the Porsche Dealer).
• Cell Delta: 11mV (Seems well-balanced).

I’m puzzled by the 7% gap between the car estimate provided by Porsche dealer (84%) and the independent AVILOO measurement (91%). Since the dashboard range is calculated based on the BMS value, the car is currently "hiding" a significant chunk of usable energy.

My Questions:

1. The "Below Average" Rating: AVILOO benchmarks this car lower than typical Taycans at 30k km. Given the BMS is even lower at 84%, should this be a red flag for long-term ownership, or is it likely just a case of the car sitting at 100% SoC on the dealer lot?
2. Bridging the gap: Is it possible to "wake up" the BMS to recognize the 91% capacity measured by AVILOO? I’ve heard about the 5% to 100% deep-cycle recalibration on an 11kW AC charger—does this actually work to force the BMS to update its SoH readout, or is it just wishful thinking?
3. Dealer Calibration: Since the dealer provided the independent report showing 91% but the car only admits to 84%, should I insist they perform a workshop-level battery balancing/recalibration as a condition of sale?

I absolutely love the spec (Neptune Blue / 21" CT wheels), but I want to ensure I’m not buying a battery that’s prematurely aged without at least getting the software to reflect its true physical capacity.

Thanks for your insights!

Sponsored

 

[targa666]

The 84% on the display is not the SOH but SOC.
SOH cannot be read out in the car, only by software at the dealer

 

[Swissdude]

The 84% on the display is not the SOH but SOC.
SOH cannot be read out in the car, only by software at the dealer

Thanks for the heads-up, but to clarify: I am definitely talking about SoH privoded by the dealer (84%) , not SoC .

 

[targa666]

Thanks for the heads-up, but to clarify: I am definitely talking about SoH privoded by the dealer (84%) , not SoC .

Oh. Soryy I misunderstood! Thought you meant the one in the display!
In that case it’s odd to have a huge difference indeed! The dealer should be able to explain this though

 

[Sace]

I have found the internal BMS SoH wildly varying. If you recalibrate it following the procedure mentioned many places on these forums it will most likely jump up to something close to what the aviloo test shows. Mine dropped to around 85 and after calibration it's back up to 91. This is by the way also where it has been for more than a year now. I would not worry about it.

 

[Swissdude]

I have found the internal BMS SoH wildly varying. If you recalibrate it following the procedure mentioned many places on these forums it will most likely jump up to something close to what the aviloo test shows. Mine dropped to around 85 and after calibration it's back up to 91. This is by the way also where it has been for more than a year now. I would not worry about it.

Thank you Sace, good to know. I have read indeed many posts about recalibrating.

 

[SergeyIndy]

I do not see anything unusual and would not hesitate to purchase.

Dealer BMS reading indeed is a point in time and with recalibration, that you can do yourself at any time, can be improved as @Sace mentioned. Also, you can read SoH using an OBD reader on your own.

 

[Tooney]

Be aware that voltage differences between cells and modules at a given state of charge can be important in determining whether HV modules might need to be replaced.
SoH is a "sort of" indicator for capacity but it does not indicate whether or not that battery might have modules potentially needing replacement.

 

[Jasper4S]

To me, a SoH of 84% for a MY21 is acceptable. 91% of course too, so in both cases, whichever one is right, I would buy it if it was the spec I love.

 

[Swissdude]

Thank you for your feedback guys !

 

[SergeyIndy]

Thank you for your feedback guys !

We got you! I would go and get it before it is gone. We can help you get your OBD and you can measure and rebalance all day long. Also, not sure about where you are but typical factory warranty on the battery is 8 years or 100k miles, so if something goes wrong it is a hassle but you are covered. Also, full battery replacements are now only the latest J1.2 build and chemistry with J1.1 emulation.

 

[Swissdude]

Thanks guys! I have an appointment set for Saturday to review and test the car. Hopefully, I’ll (finally) become one of you! Keep you posted

Sponsored