Battery only lasts 3 days .. new starter and battery also hot start issue

Hi Guys i have a 2002 996.2 thats driving me mad.. i have it the last 12 years .. i changed the starter 18 months ago as it had a terrible hot start issue , i also got a new battery at the same time. now the battery only lasts about 3 days ... i charged the battery up to 100% i drove 100km and when i got back i tested the battery and it was only at 75% i think i have a battery drain and a separate issue that the battery is only charging to 75 % whats my next step .. Y cable / alternator and possible battery drain ? anyone have a similar issue Hi from Dublin Ireland My 996 C4

You will want to measure the drain by attaching an ammeter to record the milliamperes being drawn. Make sure everything on the car is off when you do this. Sounds like you also might have a charging issue, so yes, ground straps and cables are the first thing to check. You can also check alternator voltage gain after starting the car to see if you are getting at least 13V, up to 14.4V at the battery terminals, or if you are careful, other connections on the car near the alternator. Don�t expect to always get 14.4V, as this car will reduce voltage to 12.5-13V once the battery stops accepting a certain amount of current (charged).

A DMM, and Charles are your best friends. You Tube Or if you have access to a scope, and amp clamp, you can do it the old school way. I suspect your y-cable may be/be contributing to/ the issue.

Hello Dublin ! Can you provide additional info on the hot start condition ? As other members have mentioned, using an multimeter at the battery with a Parasitic Draw Test Switch should be your starting point. Remember to latch the hood latch switch so the ECM will completely power down, allowing you to get an accurate reading. Once you have confirmed that you actually have a Parasitic Draw, you can move to the voltage drop method across the individual fuses to narrow down the offending circuit. Remember to also latch the door latches if you are going to get into the fuse voltage drop method. I usually tape them off as a reminder so that when I am done I can unlatch them. This way you don't inadvertently try to close a door with the latch in the closed position. Also double check the ground strap at the left rear of the car between the engine and the body, in behind the right rear wheel. Cheers Brian

What does your ammeter gauge read with the engine running? Should be close to 14V. Thoughts are y-cable and then alternator (sometimes the diodes go bad and it drains the battery). You can check that by having the car sit overnight (cool) and put your hand on the alternator. If it is warm to the touch, bad diodes.

My (non Porsche) co-worker had new battery woes in his truck, he took to his local indy, and they diagnosed it to a faulty seat back adjustment motor, the switch was on / always trying to move the seat. RAM tough. Tough on batteries. Anyway, something is draining your battery. I have a brand new AC Delco in my 996.1 and it went dea on me after the car sat for a while. So I have similar problems. I keep a CTEC tender on it, and I carry a jump starter battery. In the frunk. So I really should get around to fishing that emergency frunk release out and making sure I know how to get at it...

The cable that provides power to the starter can get really corroded. My dad used to have terrible hot start problems and replacing that cable completed resolved them. The car would still start when hot but it would just barely turn over and sounded super tired.

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measure the voltage across the battery while the engine is idling. it should be 13.4 or 13.6 or greater