Hi, in the last 15 years I have never replaced a battery before they were 5-7 years old. BMWs and S-class Mercedes. The OEMs lasted usually longest 6-7 years. The others about 5 years. I have an original BMW battery in my 750i and it was manufactured 1996. I would not install anything. Just use a small battery charger because you actually just need trickle charge. Have somebody measure the current to see if there is an excessive drain. Regards Ekkehart