[Jaak]

I have had a problem with my Battery for about a year now and decided to finally replace it. It would not hold a full charge over time and I had to keep charging it monthly. It was constantly at 35% after a month - 11.7 VDC. Since I did not drive it daily I thought it was due to the part time use. Now that I have retired, I use it almost daily. The battery dropped back down to 35% after 2 weeks and
I did not check it before that to see how it was dropping. My 2010 F150 has been sitting for a week and it's battery was at 85%. I also checked the charging voltages and they are within spec. Battery would not hold a proper charge.

Off I went to find out what battery I needed. The one in the car was a Napa 48-6 which a PO had installed some time in the past and it seemed "shorter" than what had been in there in the past as the bolt hole had signs it was used. It seems that the Group 48-6 is the wrong battery for the 2002 S with TIP. Research I had done indicated that a Group 94R is the CORRECT battery for my TIP. What I finally decided on was the WalMart brand EverStart® Battery MAXX-94R which had received excellent reviews from multiple sources including Consumer Reports. There are others out there, I chose the Maxx as the price was right, has a 36 month replacement warranty as well as a 108 month adjustment warranty as well. Special thanks to Mike Fockes Web page for setting me in the right direction!

The Battery has 790 CCA (cold) and 960 (warm), fits correctly into the battery tray and the hold down bolt fits in the correct hole (according to previous battery before the Napa). It seems the pre 2005 Boxster need the "optional" listed battery which is the Group 94R VS the Group 48R which the basic battery in most lookup books. If you have a TIP, you need the 94R and as Mike has stated any amp installed as well. Those with a group 48R may want to upgrade to the 94R if they have any issues. Mike also recomended those in colder climates should move up to the 94R. The battery does come with covers over the terminal and the POS. terminal cover has the plastic plug "punched" to seal up the unused vent port. You reuse the existing vent plug. After I replaced the battery the car does seem to run a noticably stronger with faster starts etc.

A curious thing is my CEL would come on indicating Secondary Air Injection issues. I had gotten the system fixed at my friend P-Car Indy shop. No Vacuum leaks and all devices are working well. It may be the the reference voltage is low due to the bad battery causing both the left and right banks to indicate a failure. The CEL would disapear after a while (after the battery was charged from 35% to 100%. I will keep an eye on this.

Hope this helps others out as well. It seems the Group 94R is the correct battery for the 986 series of cars. Post 2005 cars all have 94R as the standard battery from what I have seen online and severl lookup books. Pre 2005 should also use the same Group 94R battery.