2017 FFE Normal battery degradation?

[vkdyer]

My range has dropped over the last couple months. Since my last full charge, I've driven 85.5 miles over 3 days with 8 trips. The battery shows 10% remaining (and only 5 miles). If I add up the kWh for the 8 trips, it comes to 18.5 kWh. The battery has a stated kWh of 33.5. So according to these numbers, I used 90% of the battery but only 18.5 kWh. The car will be 8 years old in April. Is this normal degradation or does it sound like something is wrong?

 

[jghall00]

If you use Forscan, will tell you the remaining kWh in the pack at full charge. Mine was around 25.8 with 68K.

 

[Anti_Climax]

My range has dropped over the last couple months. Since my last full charge, I've driven 85.5 miles over 3 days with 8 trips. The battery shows 10% remaining (and only 5 miles). If I add up the kWh for the 8 trips, it comes to 18.5 kWh. The battery has a stated kWh of 33.5. So according to these numbers, I used 90% of the battery but only 18.5 kWh. The car will be 8 years old in April. Is this normal degradation or does it sound like something is wrong?

33.5kWh is not the available capacity, it's the direct raw capacity of the cells. 100% is 95% SoC and 0% is about 8.5% SoC. So even when absolutely brand new, the available capacity is 29kWh. What you're seeing here suggests your capacity has dropped to about 70% of the nominal value.

If it's been abrupt and recent it could be a single cell triggering the discharge limit before the other cells are near it. In which case the capacity is there but it can't be safely used without drawing a cell down below spec. Going too low on series cells can do REALLY nasty stuff like flip their polarity.

Beyond that, they do have a finite lifespan that targets around 80% after 8 to 10 years. But that is tied to a bunch of factors that vary widely by drivers. At 4-5 years, my original battery had lost around 25% of the available capacity but I have no idea how the original owner treated it. My replacement hasn't degraded nearly as much in the same timeframe.

 

[vkdyer]

Thank you both for your replies. I've got a charge log going back to day 1 (April 2017) and a trip log back to March 2023 (after the new tires I put on dropped my range), so I have numbers, but not the knowledge for interpreting them. I tried using my OBD scanner on it and couldn't get it to connect, and I've read enough now to know I'll need a different one to try Forscan. I've loved this car so much, but with the range going under 100 miles now, it's getting to be a problem. (I once got 140 miles out of it in the summer time.) Since the battery warranty is running out soon, I'm thinking I will need to trade it while I can still get something for it. This is a great little car, and if I could wave a magic wand and get a 200-mile range, I'd keep it forever.

 

[Anti_Climax]

You can get the capacity without Forscan, it's just more tedious. Top it all the way up, clear one of your trip meters, drive until it's nearly at 0%, and then park it and run the heater until it hits 0. You're 90% of the way there, so I wouldn't expect it to give you a drastically different reading than what's been estimated here ForScan will let you check cell voltages to see if any are particularly problematic.

But there's no single range that's "good enough", it's always "good enough for you". Someone else could get a few more years of of it.