911/ 996 Battery woes

[britdave]

Why does the 911 / 996 have so many battery issues,like it wont start , due to a dead battery ? I have 3 other cars ,with no problems like this. I love my 911, but this dead battery issue is really getting me down.

I use a Porsche battery tender, but even then it will let me down, when I travel some where . A friend told me that the "electronics in a 911 are running all the time ,and that causes the drain" is this true ?

Anyone know the answer , or a solution ? HELP !!!!!

[Alfieboy]

They are really heavy on battery, it's true. I am on my third battery type (all dealer installed) and I still get back from a 2-week business trip to a car that I have to unlock manually as the remote can't activate due to low battery. One can hardly use a battery tender at the airport car park. Is it unique to 996's?

[Dharn55]

The remote unlock feature deactivates after a few days (5 I think) specifically to avoid draining the battery. It has nothing to due with the battery being low.

[Alfieboy]

Ha! Nice to feel like the dealer recommended different batteries than explaining that which you just did. $500 a pop including installation.

[whall]

The Owner's Manual is your friend. If you don't have one, you may be able to find one to down load here at RennTech. If you can't find one for your year car, you can order one through you dealer for about $30.00.

Having said this, it sometimes takes reading through the Owner's Manual to find important information not found in the table of contents or the index. In this case, however, the remote control shutting off is explained on page 19 of the MY03 Owner's Manual (found here on RennTech).

Bill

[britdave]

But any explanation why these batteries let you down ? This is a major problem with 911's . A friend of mine got rid of his for this reason alone,other than that he loved the car,but after a week or so (being out of town etc) the battery would be dead and the car would not start of course. Anyone know why these batteries drain so fast , compared to ANY other car ? Cheers Dave...

[Loren]

These batteries do not drain faster than other batteries.

If they do then it is likely because someone has added things to the car that are using power when the car is off (like a radar detector) or there is a problem with some component.

[JFP in PA]

Loren is correct; modern SLI (starting, lighting, ignition) batteries are better at reducing their rate of self discharge than they were years ago. The problem lies in the every increasing number of "convenience" items added to just about all cars these days (on-board computers, alarm systems, sound systems, navigation equipment, etc., etc.), all of which constantly draw low levels of current while the car is shut off. Standard "stand-by" current draw on these cars from the factory in in the range of 40-60 mA; aftermarket add-ons simply increase that load. We have seen the "native" current draw in a Boxster nearly double just from a cell phone charger left plugged in without a phone connected to it. As the battery ages and naturally loses capacity, these drains start to take their toll. This is exactly why battery maintainers have become a big business these days...............

[britdave]

Thanks guys,but my 996 is "totally" stock ! I only have a radar detector attached,no cell phone "NOTHING" else, but I "ALWAYS" unplug it upon arriving home into the garage. The "only "drain I can think of is the red light that flashes in the center by the radio, could that be the drain ? I don't even lock it in the garage.

While I was on holiday in the UK and europe for 7 weeks , I left the Porsche battery tender hooked up the entire time. Got home and it started right up. Drove it a few days then parked it again,this time without the tender hooked up.

About 5 days later,I went to start it,and dead again. This is a new battery from the Auto zone (Which are rated #2 in the USA ) It seems I must ALWAYS have to plug in the tender all the time. I feel like I'm charging my kids old Hot wheels jeep he use to have. By the way I got that battery in Jan 2010,and took it back for another one "gratis" so we shall see how this one fares ? I understand many guys have the same problem,and when I go out ,I always carry my B&D jump start ,just in case !!!!! Dave.....

[RFM]

The procedure for minimum power drain is key out of the ignition and car locked, this is the basis for further investigations.

[Si James]

I have never had any issues with my battery. I do travel often...two weeks at a time in most cases and my car is fine when I get back. I do have a 1987 190E that has a Priority Start! 12 Volt ProMax

" an automatic computerized on/off switching system protecting battery voltage and starting power. If battery voltage drains below 11.7 volts when engine is off, it automatically disconnects the load. The battery voltage immediately recovers. TO START: just step on brake pedal, starting power is automatically reconnected. Designed to handle 1000 starting amps" Simple to set up and it works.

[JFP in PA]

I have never had any issues with my battery. I do travel often...two weeks at a time in most cases and my car is fine when I get back. I do have a 1987 190E that has a Priority Start! 12 Volt ProMax

Problem is that this setup will cause issues on newer cars (built after 1996) if it cuts power off to the DME (and if it does not, you still have power drain taking place), which will then lose anything the DME has learned, and will reset the DME's "I/M Readiness" mode, meaning the car will not pass inspection in most states as the emissions section will read "not ready" until the car has driven multiple cycles/miles.

Charge and load test the battery; it is good, get and use a maintainer. It's one Hell of a lot cheaper than a $100+ device that creates more problems than you had to begin with………..

Edited September 8, 2010 by JFP in PA

[ssp996]

My original Moll battery on my 01 996 lasted 9yrs. Just replaced in April. Car is daily driver Mon-Fri. If car sits unused for extended periods of time, the batteries will drain and not fully recharge, even on extended drives. Also, I have read somewhere that if you don't lock the car doors routinely, there is more electrical drain that occurs than if car is fully locked. Don't know how true this is

[carsareart]

I am thinking about installing a battery tender. Where are you guys installiing the charging leads?

[Mother]

Even with battery charger it will drain fast if alternator is not working properly.

[02tx996cab]

A Porsche battery discharges as the car slowly dies from neglect and the shame of not being driven...

More seriously:

-- the remote-actuated central locking system drains some power, but shuts itself off after 5 days as Dharn55 notes

-- alarm system stays on (the blinking red light) as long as there's battery power

-- etc. etc. (others have said it, I won't repeat it)

I recall that, if you lock your car manually--not using the remote--the central locking system doesn't fully power up, saving you a few milliamps.

Both a good buddy and I have 996s. 2 weeks unattended is no problem, beyond that and sometimes the battery gets low enough to be unable to start the car. A trickle charger/battery tender is your friend if you must leave the car in the garage for an extended period of time.

[02tx996cab]

A Porsche battery discharges as the car slowly dies from the shame of not being driven... :(

More seriously:

-- the remote-actuated central locking system drains some power, but shuts itself off after 5 days as Dharn55 notes

-- alarm system stays on (the blinking red light) continuous, using power, until there's none left

-- etc. etc. (others have said it, I won't repeat it)

I recall that, if you lock your car manually--not using the remote--the central locking system doesn't fully power up, saving you a few milliamps. The owner's manual notes this and a few other things to do if you're going to leave the car undriven for a while.

Both a good buddy and I have 996s. 2 weeks unattended is no problem, beyond that and sometimes the battery gets low enough to be unable to start the car. A trickle charger/battery tender is your friend if you must leave the car in the garage for an extended period of time.

[PeterC4]

I own my second 911 both 996 variants. The real issue with the battery life is the car not being driven often, or stored in the winter without use of a trickle charger or proper maintenance. Otherwise, I have had no issue with the battery. Assuming you have no cell phone chargers, radar detectors or other devices plugged in, there has to be something draining the battery of its power when the motor is shut off, that is unexpected. Secondly, a battery that has been drained then re-boosted is always weaker and prone to problems. I would check your alternator if you are having consistent problems. Also, look at your voltmetre when the ignition is on...is it reading under 12 volts? Finally, at night, with the ignition off walk around the car and look closely for any lights that might be on unexpectedly.