I would advise to replace the battery w/ OEM from Sunset Porsche in Oregon. They sell OEM parts at cost +
actual shipping. I got one from them a couple months ago and they don't make money off shipping.
Once you recieve the battery, you must take it to local porsche dealer to be filled with acid at no charge.
Then, climb into the hood and have someone hand you the battery! do not lean on passenger side fender and swing the battery into place. you will dent fender as i did.
thank goodness for paintless dent removal
You will need to reset your radio after that with the radio code.
Your car may act funny (slow starts, warning lights off and on so on... keep driving the car will reset itself, then you should be good.
If its your alternator, I don't know what else to advise besides, take it to the dealer.
