Car starts fine in AM but after succesive starts battery becomes weaker(UPDATE)

I've noticed this in my new car (2003 C2). It starts up with a strong crank in the AM. After a couple restarts after making stops the battery becomes progressively weaker. It charges steady at 14 seems like constantly. Today after making a few stops it almost would not start on my last stop (to get gas) but it did catch.

Yeah, it's not your battery. it's actually considered normal as crazy as that sounds. It sounds like the starter is about to give up the ghost but that most likley isn't the case. as your car reaches operating temp, the internal engine parts increase in size causing the engine to have it's full compression. When you are starting up a warm car the starer is fighting against the majority of the 11.3 compression ratio making it a bigger chore for the starter compared to startup. I have a 03 C2 with the exact same "problem". It has never failed to start no matter how many times I restarted the car hot.

geez, that does sound weird. thanks

My car had the same problem, new startermotor did the trick.

Also, if you're making multiple short trips in a row you may not be giving the generator enough time to charge the battery.

If it is the original battery it is now 7-8 years old and it is probably time to replace it anyways. They can test it at most parts/battery stores. I got my Bosch battery at PepBoys. Same size as the OEM battery, I think Bosch makes them for Porsche. Cost about $120. Have them test the old one for you, you may have to take it out to do this. Also, when starters get old they start to loose some power which could explain this. And check the ground strap from the engine to the body, behind the right rear wheel. I had intermittent starting problems on my car, replaced the battery (which needed replacing anyway), then the starter, then the ignition switch. Still had the intermittent problem. Then I saw a post on the ground strap, removed it, cleaned the strap and the contact points, put it back on, problem gone and it has never happened again.

Replace your battery.

It was my battery when I had the same problem. Car didn't even turn over some times after warming up. Cranked like a champ first start of the day though. I believe if in the last year of a batterys life and any signs of a problem you should just dump the thing. A dead battery is no fun stranded. Can't crank the music as loud

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Uh, no. During engine cranking and even at idle the actual pressure generated in the cylinders is low cause the throttle is not open but just a tiny crack. Also, valve timing even life (in cars equipped with VarioCam Plus) works to limit cylinder filling. Also, you're ignoring the considerable drag by the cold oil when cranking a cold engine. The cost in terms of the amount of cranking energy required in compressing the air/fuel to the 11:1 or whatever is almost fully recovered cause the compressed air/fuel acts as a spring to help get the piston started down the cylinder as the starter turns the engine to the point the cylinder is now on its 'power' stroke. If the DME is putting fuel in the cylinder and triggering a spark then this spring action still acts to help move the piston down the cylinder as the mixture begins to burn. A warm or hot (operating temperature) hot engine requires less energy to get spinning. The OP's symptoms sound like a classic bad battery. A start consumes some charge and the battery can't recharge/recover in the short time the car is driven. I'd advise the OP to have the battery checked once in the AM then again later in the day. Just in case the battery proves to be ok -- got to cover all bases... -- this same shop should have the ability to perform a checkout on the alternator, but my money (theoretically speaking) is on the battery. Sincerely, Macster.

+1 on Macsters comments. I had exactly the same symptoms for about a year, then the battery failed to fire the second start of the day about a month ago. Fortunately, I was parked on a spot where i could do a roll start and it fired right up. Replaced the battery immediately (I was on my way to the dealership anyway - it was my scheduled 2nd stop, that day anyway). No problems since. No symptoms. Fires strong all day long regardless of the number of stops. Voltmeter shows no sign of drainage throughout the day. However... there is a parallel thread going on here about a similar problem and his was apparently fixed by replacing the alternator. So have them BOTH checked out by a competent mechanic with the right devices.

When you crank do you go below 9V? If so, weak battery. Sounds like your starter is going bad if it can't hot start but cold starts fine; Porsche will replace that under warranty for that reason if you still are covered.

Visually check you battery terminals for corrosion. Check your battery voltage. Burn off surface charge first by turning headlights on for 30 seconds. 12.6v is fully charged while 12.45v is only 75% charged and 12.3v is only 50% charged. Check your alternator output next for proper voltage and amperage You should check out how many amps your starter is drawing. IIRC 250-275 amps is normal. Battery drain is a symptom of a bad starter especially with short trips. Lastly, check voltage drops on the grounding circuit. Should be less than 0.2v at 1500-2000 rpms. This was the cause of a hot start problem with my 911sc which I originally suspected to be a starter failing. If you check these items you should be able to track down your problem quickly A Sears 73756 clamp on ammeter is very useful to carry these simple tests

Oh boy impart knowledge. I know it's a mistake to give another car a jump. Especially if the other person is handling their side of the jumpers. Problems like alternator or even battery is my side of the story on giving others a jump. The load of a completely drained battery on your alternator and battery aren't good for it. It's almost or as bad as shorting your battery out. I'm not sure but I think the heavy loads from a dead battery draining yours can ruin a cell. I figure the alternator can be slammed pretty hard trying to make up for a dead battery. For the last few decades I've been just driving by people needing a jump. Not nice but one of the last times jumping a guy my alternator and battery took a major hit from a fool. Screwed a cell or two in the battery and blew my diode stack.

Thanks for all the input. I was hoping for a clear fix. Oh well, today I will take it to my mechanic friend. He loves to trouble shoot. Just didn't want to bug him if not necessary. I will post findings...

complete electrical check : battery, alternator, starter. It's the battery. Nearest Costco doesn't have any. Local NAPA had one. Manufacture date 2008. NAPA ordered a new one for me and said it be an Interstate. $108, Will get in 2 days. No other parts store here.

I bought my last at Walmart, 4 year free replacement, and around $85, best price and warranty around.

Thanks for the update!

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+1

Glad you got it sorted out and it is just a battery. I tend to replace the one in my pcars about every four years and keep the old one for a spare or jumper battery for my sailboat or toys... A fresh battery in a pcar is cheap insurance, IMHO.

A CLEAR fix. Remove, clean, burnish, and tighten the battery posts and connections and ALL "power" connections between the battery (front) and the alternator(rear).