You can buy the battery cheap on amazon: http://amzn.to/2jE8BJX


Sections in the video:
0:13 Batterychange
2:34 Key chain and transponder change
5:26 Key remote opening
8:17 Key remote change
9:54 Note about the transponder


Transponder details:
Manufacturer: NXP (before Phillips)
Modell: PCF7946AT


This works for:
Lancia Y / Ypsilon (846)
Lancia Musa
Lancia Delta
FIAT 500
FIAT Doblo
FIAT Ducato
FIAT Palio
FIAT Punto
FIAT Scudo
FIAT Sedici
FIAT Stilo