The cells can be replaced with the new technology ones used in the 30 kWh SoulEV, which last much longer and have improved capacity (28.8 kWh I think), but it may be necessary upgrade the BMS firmware.

Anything more ambitious would require extensive change to the BMS.

 

Kia do fit different better cells for battery warranty claims. Not sure there is any commercial route to get them fitted on request, as an upgrade.

 

PS548 Kia Technical Service Bulletin (tsbsearch.com)

If they have reset the BSI, it will need seversl cycles of recharge to get back to showing true data. The above TSB instructs them to get the data before doing that. Are you measuring with SoulEV Spy?

 

I measure the added current - the meter on the plug, or the indicator on the DC charging stand. I have driven the car several times (and used the last bit with the heater) to 0% and immediately charged slowly or fast on the dc. Each time it was less than 70% of 27kwh and that should be a better than realistic value because it doesn't account for charging losses, charging cable resistance etc. I started to address this after my range dropped by leaps and bounds. I bought the car more than a year ago and after I learned how to drive economically, I was driving at temperatures between 15-25 with a consumption of around 14kwh per 100km and the range of the car showed between 150-170km. I was thrilled with how well I had bought. After a few months under the same conditions, the range dropped dramatically and I was getting the most fuel efficient driving at barely 130km. After four different measurements in authorized service stations when their results differed significantly from themselves and from reality, I finally started browsing the Internet and found out that there is this program. I'll take my wife's old android and tomorrow I'll plug in the obd...

I was most frightened by the rapid - leap - drop in range, because in about four months my warranty will expire and I am afraid of another drop and thus the devaluation of the whole car

 

The only data KIA accept for battery replacement under warranty is the SOH measured by the BMS and accessed by their own diagnostic equipment. You can access that data with SoulEVSpy and an Android phone or tablet. Spy will also show the voltage of each cell pair in the battery, and let you see which cell(s) may be causing your issues. With that data, go back to a KIA dealer with a copy of PS548 and insist it is followed exactly.

EDIT: As you seem to have a 27 kWh battery, Spy cannot get the SOH directly from the BMS, so it calculates a value from the data presented.. We don't know if that value conforms to that which the KIA diag equipment accesses, but it is believed to be close. In any event, the cell data should give a convincing indication, and you always have the option of contacting KIA Customer Services directly, and also the Consumer Protection Authorities in your country.