Alternator or Battery problem-How do you tell?
 

Hello,
Newbie to this forum after defecting from 911 a few years ago and now Boxster is out of warranty.

The battery in my 2003 Boxster won't hold a charge. The battery was replaced at the dealer two years ago with Porsche battery. Live in Chicago and had car on lift pretty much since October (maybe driven 2-3x over winter) without Battery Buddy or trickle charger.

I opened the cells and topped off with DI H2O yesterday and charged battery with my charger. Starter turned over but sluggish. Drove for 15 minutes. Pulled car in and attempted restart-VERY sluggish and would not start.

I am 90% sure this is a battery problem but how do I tell? I am probably going to replace the battery anyway. Do you recommend aftermarket?

Thanks.
Glenn

Welcome to the forum. It's easy to check your alternator, hook up a volt meter to the battery and start your car to see how many volts the charger is putting out it should be over 13.5

Harry is correct on the alternator voltage, but we prefer a systems load test that not only checks the free idle voltage for the alternator, but also checks it under load to make sure the voltage regulator and diodes are up to snuff, and then static load tests the battery which is the only way to assure it is good or bad. Entire process takes about 5 min., and some parts stores will do it for free.

Charge the battery fully to 14.4 volts making sure it is topped up charge-wise. Then at at least 4 hours after disconnecting the charger, take an open circuit voltage reading by placing a digital voltmeter across the battery terminals. It should read at least 12.7V.

An open circuit voltage (OCV) is one where the battery is disconnected from the vehicle, but you can also take that measurement with the battery connected provided nothing is turned on, such as dome lights, etc.

Next, perform a load test of the battery. A carbon pile load tester can be bought at Harbor Freight for about $80 - wait for a sale. It can also be used to test the charging output of your car as well.

A load test is performed at one-half the CCA of the battery. The CCA of your battery will be about 700A and it is listed on the battery. That test is done for 15 seconds and the battery voltage should not drop below 10.5V.

Also, with the battery in the car and the car running, you should see 14.0 to 14.4 volts across the battery with the RPM off idle or about 2000 RPM. My on-board voltmeter reads 14.1 to 14.2 V all the time.


Porsche does not make batteries. I personally chose to go with an East Penn battery (648MF in my 993). They are a direct fit and other than case color, is 100% identical to the Porsche Moll-Kamina that was in the car.

No reason to buy anything but an aftermarket battery for a boxster. A list of those known to fit with 3 year old prices is at batteries - mikefocke2. You really need that battery maintainer for the winters up there. No battery will survive the drain however slight of the electronics in a modern car with all the "waiting for you to put your key in the starter switch or click the remote" stuff for months without one which really sucks the life out of the battery especially when done for successive winters. Old cars without any of those modern conveniences would but not newer cars. I really doubt it is anything but your battery.

Sorry, Mike, but not true. If the alternator is not providing the battery with sufficient enough voltage to maintain/charge it. Essentially the car is running off of the battery then. The battery will go dead again. If the car is sitting or not.
You can buy a cheap volt meter and Radio Shack and like Harry mentioned. Measure the voltage at the battery while running. It should measure between 13.5 to 14.5 volts. Or at least a volt more than the battery is reading at rest.

I do agree that some type of battery maintainer should be used if the car is going to sit for awhile.

Just my 5 cents. Considering inflation and all.

Randy

Randy, I'm not disagreeing. My points were three: Don't run down your battery over the winter. Don't need to spend on any special battery. Given the OPs history, probably the battery.

Do I have a VM and a Load Tester? Yes. But for every time I've had a problem (at least 30 over my life time) it has been the battery that cured the problem and given the history of battery abuse in the OPs story (two winters with total draw down)...

Assume it is the battery, go get it tested and replaced at someplace that doesn't change a lot for what is a generic part.

Thanks Gentlemen,
I replaced the battery, checked the charging system, and all is well.
Glenn

Gotcha, Sorry for the misunderstanding Mke. Looks like all is well now on his end.

Randy

Old thread same problem. It's winter here in Utah and I haven't started the car for a at least month and 1/2 - my bad. I jumped the Porsche and let it run for 15 minutes and then took a 6 mile drive. DOA this AM. Bought battery charger and I'm charging (gee wiz another car toy tool ;) ). I'll try the voltage test mentioned above in the AM.

BTW - The battery is a Porsche Brand and was just bought this summer on the day of the Concourse event I was in for the National PCA convention here last summer.

88 911 CAB

cics ... that is as old as your car. They still use it?

On the battery though, you jumped, started, idled for 15 minutes and drove only 6 miles under unspecified conditions. I don't see that charging the battery greatly.

Your charge overnight will help, then go run at speed (not idle) during the day with accessories off for a good 20 miles and come back. Now let it sit and test the voltage and then see how it starts. Bet things improved. Put the battery on a maintainer (not a charger or charger setting) if you expect the car to sit 10 days or more.

Generally, a charger is not a maintainer and vice versa. Though expensive units can sometimes switch between functions.

Why open a new thread when an old one will do.

Anyway, the NEW battery charger seems to have done the trick. Battery measures 12.4V with car not running. Some other threads say to disconnect the -battery terminal wire and if the car still runs, then its the battery. While I didn't do this, seems like a good idea to isolate alternator or battery.

I think a trickle charger may be a good idea since this winter has not been a great one for PCAR driving in UTAH.

As usual no good deed goes unpunished. The hood shocks are shot. This will be the second time I have replaced them. So, no more Porsche brand. Need to get the ones that have the lifetime guarantee.

I just left my 2003 S with the negative battery terminal disconnected here in cold Wyoming (no trickle charger) while I was gone for 2 weeks. It read 12.5 v when I got home. On the 2003 the radio has no code to reset. DO NOT disconnect the battery while the engine is running! It will fry the diodes in the alternator.

Good to know.

A maintainer maintains the charge and only use a very tiny rate of charge which allows it to stay connected over weeks, months. Most maintainers won't charge a dead battery, they only come on at a higher voltage than typically found on a discharged battery.

A typical trickle charger or a charger uses a higher rate of charge and could fry the battery. There are high priced units that do both but most don't.