blazian87 10+ year member
CarAudio.com Elite
So I just helped do a battery swap and amp swap for my buddies 09 Lexus IS 250 last night. He's been using the same OEM battery since he got it and it's been dying on him on a few occassions. We swapped out the battery with a fully charged and healthy deep cycle XS battery. Resting voltage was around 12.8v before installing it. I checked the voltage with both batteries and it reads 13.4v while the car is running on both scenarios. That immediately made me suspect that the alternator is going bad. The alt location looks like it might be a bit*h to get to and install. I'm guessing that the alt was overworking itself bc of the dying battery and caused some damage. But now that we have the new XS battery in. Everything's working pretty nicely now and car starts up no problem. If we were to just leave the same alt in with the 13.4v, would it damage this XS battery eventually and die much quicker? I don't know if 13.4v is normal for this car but it seems unusually low as I'm expecting it to be in the 14v range atleast while the car is idle and with no A/C and no music.