Charging to only 80% for an Audi PHEV with an 8.8kWh battery is not necessary, especially since Audi created a very large buffer, leaving more than 25% of the battery without access to charging to protect it. Also, charging to 100% using a level 2 EVSE is not damaging, unlike doing the same with a DC fast charger that sends the power to the pack at a much higher rate and begins to slow the charging at 80%. Level 2 charging is never that fast and it does not damage the battery pack. If Audi personnel have told you that it does, or you are using Tesla guidelines (for DC fast charging), neither is reality with slower level 2 charging.
Our first BEV was always charged to 100% (LiFePO4 chemistry) and it maintained 110 miles of range for all 4 years of our ownership and 40K miles. How can a cheap 2012 EV battery pack be that much more durable with double the miles in half the time? The Lishen LiFePO4 battery pack from China was a much higher quality product, unlike what many pundits claim about products from China.
We have ONLY used level 2 EVSEs at no more than 16 amps, because that is all that our 2017 A3 Sportback e-tron is able to accept. We are still less than 22K miles and have dropped to a maximum of under 70% of new state of charge, often dropping to between 40-65%. There is absolutely NO REASON why our battery pack, which has been used so little over 7 years, should be in such a decline. What I have discovered online from experts in the field is that Audi used lower quality lithium Ion pouch packs, rather than the higher quality that other manufacturers used. They have since upgraded to better quality battery manufacturers, but that leaves the first adopters with poor quality battery packs on our PHEVs.