jennifer911

As mentioned, there are a dozen or more settings that your car’s computers will have to relearn after a battery disconnect. As you know, murphy’s law states “anything that can go wrong, will go wrong” One way to save doing some difficult manual resets is to use a small cheap Memory Saver. This is a plug that goes into the cigarette lighter or power plug receptacle. It has a 9-volt radio battery. Since it only takes 5 volts to support all the memory functions, this unit does the job. Before disconnecting the car’s battery, plug in the Saver, shut the doors and take the bulb out of the trunk light. The inside lights and trunk light will drain the little 9 v battery if you don’t.

When we changed the battery in our 997 we simply used a little 12 volt battery hooked in parallel to the main battery’s wiring. Don’t use your battery tender as it will shut off unless it senses a few volts in the system.

jhbrennan

Good input - google "9 volt battery memory saver" and you get more info.

LexVan

I also always like to recommend when working on/in the battery area to wear eye protection and rubber gloves.

ATSR

I didn't use any supplemental power source while replacing the battery and all the settings remained intact except the clock. Radio station presets didn't get deleted, and I haven't noticed any PCM preferences that changed.

Spinout

I use my Battery Tender to keep the memory setting alive when disconnecting the battery.

jennifer911

You have to carefully read the battery tender instructions before using it for a power source. Unlike a regular battery charger, most battery tenders produce no current unless they measure a certain minimum voltage in the car’s battery. When you disconnect and remove the car’s battery, the tender may keep flowing current for a short while, but it would be a very unstable situation and the tender could switch off.

If you have an old 12-v alarm system gel cell battery (or any battery from 6 to 12 volts) in the house, it can make a good memory saver.

TypeRx

Do you have a part number? My battery has been acting up so my 10 year old jokingly said we should put the RS4 battery in the Porsche. Wonder if it fits?

Also, any opinions on this Moll/Porsche for a 997.1? Price is right and it looks similar to my current battery but the part number seems a bit funky.

https://www.ecstuning.com/b-genuine-...y/99961106520/

jhbrennan

Moll is a decent battery...but compare its warranty to the offerings from Interstate, Wal-Mart, etc. Same for Audi option - I'd check the warranty.

wc11

I had the tender plugged in when I changed mine out a few years ago and lost nothing. No memory loss and no codes.

A battery is a battery is a battery.
As long as it's 12 volts and 700+ CCA, your fine.

Get a national brand from a national chain with a national warranty.
Then if you have a failure down the road, because it never happens at a convenient time, you 'll be able to get a replacement easily.

Specialty batteries means specialty prices and specialty store hours.

blassy

I had a total battery discharge - airbag light came on when it was replaced and is still on. Driven a couple hundred miles since and it remains on. Will just have my mechanic take a look when it goes in for end of year service before hibernation in a couple months I guess.....

orange260z

For those up in the Great White North, Walmart sells an 765CCA "Everstart Maxx" battery in the H7/94R size for CAD138 with a 36 month replacement/60 month pro-rated warranty. Availability can be a challenge, and it's important to sort through any stock to ensure you're not getting a battery that's been on their shelf for a couple of years. I found a nice, relatively new (~3 mos) one and it fit perfectly.

http://www.walmart.ca/en/ip/everstar.../6000195362562

Also, I planned to use this to retain the memory along with a jump pack.

http://www.walmart.ca/en/ip/automoti.../6000016943222

Unfortunately, I didn't realize that a switch had to be flipped on the jump pack to activate the power outlet, so I ended up having to reset the windows and showing the PSM code. As the manual says, it went away after a little driving. I don't recall, but Imay not have lost my radio presets. I definitely did not have to punch in a radio security code, which was one of my fears - having bought the car second-hand, I don't have the code.

I always use a CTEK battery maintainer if I know I won't drive the car for more than a couple of days.

jhbrennan

No radio codes for 997's...although as you stated, you may lose radio presets.

Smitten

Most newer battery tenders won't work this way. They need to sense a load - a battery in the circuit - before they will provide output. Older/simpler ones that will work this way do so because they lack 'smart charger' sensing and can overcharge your battery.

Smitten

I think battery tenders are evil - they mask electrical problems. There is absolutely no reason a (healthy) P-car can't sit for a month or more without being charged. In fact, the more recent models automatically shut down almost all parasitic loads in any prolonged period of disuse. I know my 2011 Carerra can go months without use; I have to unlock the car manually with a key but it will instantly start up.

During winter layup I disconnect the battery and never charge it over the winter. I have done this for years and years in various cars, trucks and especially large boats where the batteries weigh hundreds of pounds and removing them is impractical.

If you 'need' a battery tender, you have a stuck relay or electrical fault/short. Fix it, don't mask it with a battery tender.

GTorTT

Thanks for all the great input. Went to Pep Boys and bought the Bosch ABM battery. However, it is about an inch or so wider than the OEM battery. While the battery tray will accommodate the battery, I need to move the bolt with the lock plate to the next hole in the battery tray, but there are no threads to lock it down. So looks like I'll have to go for a battery the same size as the OEM.