Larry Herman

The battery died in my 2006 Boxster S, and it won't take a charge so it's time for a new one. Just check the Diehard site & they don't make one for it. What are you guys using?

Jim Michaels

Larry: Interstate has seemed to be the most popular non-OEM replacement battery for Porsches for years. I don't know about your '06 Boxster S, but some '06 Cayman S owners have gone with the Interstate HTP-91. It's about 13# lighter than our OEM Moll battery.

Larry Herman

Could you have meant MTP-91? Did a quick Google and that was what came up. It also was the recommendation on the Interstate website.

mooty

chuck it
buy that very $ lithium ion battery from porsche :-)

Larry Herman

Oh, I knew that I could count on you for a fiscally responsible solution.

Jim Michaels

MTP-91 is correct. It comes with a vent kit, including an adapter to fit the round OEM tube onto an oval- shaped vent hole on the battery. You may also need to move the battery tray hold-down clamp nut over one notch as the MTP-91 is a bit shorter than the OEM Moll battery on the Cayman S.

I don't know if this is the same on the '06 Boxster S, but on the CS there is a throttle valve adjusting adaptation required after replacing (or reconnecting) the battery. After everything is hooked up, switch on the ignition for 30 seconds without starting the engine. Don't press the throttle pedal during this time. When you do start the car, the engine needs to run for a few minutes before the engine control module can relearn idle speed and mixture adaptation values. Several Cayman owners who just replaced their battery have posted that their idle speed was going up and down as if it were "searching" for the right idle speed. They were right, but no need to worry.

No, I haven't gone through this yet, but plan to soon on my '06 Cayman S.

Larry Herman

Thanks Jim.

No HTwo O

This is good info. I plan to replace my OEM battery in the 2006 Boxster S early next year. I don't want to push the OEM much past the 4-5 year mark. I do use the Porsche battery maintainer, and I think this has help to extend the current life.

Larry, please let us know how the Interstate MTP-91 fits. Thanks!

FYI- you may also get a PSM warning upon the battery swap. This will go away soon after you start to drive the car.

No HTwo O

Guys, why does the Interstate web-site call out this battery for the 987S???:

http://www.interstatebatteries.com/c...879-4294492598

Jim Michaels

Interstate also "calls out" the MTP-H8 for the Cayman S instead of the MTP-91. The H7 and H8 are larger, heavier, and more expensive batteries than the 91. The H7 provides 640 cold cranking amps compared to 700 for the 91. I just mentioned the 91 as the apparent preferred Interstate choice among Caymanites.

911SLOW

I use Bosch S5 batteries on my cars.
Pretty impressive performance and durability.

John

pdxjim

I used Batteries Plus for my replacement.

tinman

The battery died in my 06 S'....so I got another one from the Porsche dealer, it died as well after a few month, even though I used the factory trickle charger, at the time the battery in my girlfriend's 2001 BMW 330i died, it looked like the same size, had the vent kit in the right place, she had her battery charged so she told me to take the BMW back to Sears....I thought "heck, I'm going to try this thing in my Porsche, it worked fine, it's called the International (for FOREIGN cars, so they can charge a premium), but it was around $160, I believe....I figured what the heck, my car's out of warranty anyway, but not the extended warranty which I bought, I know, mixed opinions, but I justified it by her engine was a 3.0, mine a 3.2....and it worked, and has been working for over a year....I gotta get rid of a buncha batteries sitting around my garage.

Larry Herman

Tinman, can you tell me what the model number is for that battery?

BTW when I pulled the battery out, 4 of the 6 cells were very low. I put about a half a gallon of distilled water in it!!! It's now on the charger and percolating nicely, so we'll see what happens tomorrow.

Larry Herman

The battery came up to 13 volts, and slowly fell to 12.75 and stabilized there. Put the caps back on, cleaned it up & bolted it back it. It started right up (after the 30 second waiting time) with no problems.

I do think that I will figure out what I want to buy, because I am not sure if this one will last.