Tone

I have a 2006 997 S.
- Batt replaced 2 yrs ago by dealer with Interstate MTP-H7.

Last week during a DE had Battery & Alternator warning lights come on.
- Different dealer said Battery was not the right size potentially causing alternator problems.
- Alternator replaced under warranty
- MTP-91 batter installed (They later confirmed they should've installed a MTP-93!!) and will provide a credit for this error.

I called Interstate and they say the car should use either a MTP-H8 or MTP-93...with H8 preferred...though can't confirm if it'll fit in the stock tray. Interstate said the H7 or 91 do not produce the specified CCAs.

SO WHAT'S THE RIGHT SIZE??

Car is currently having the batter grnd strap replaced under warranty as part of a TSB that may be the root of the problem.

Any insight would be appreciated.

Thanks

Jim Michaels

I don't know about the 997S, but someone on planetporsche.net recently posted the MTP-H8 as the correct Interstate replacement for the Cayman S as well.

jcnesq

Hmmm, I replaced the battery in my 05 997S about 6 months ago with the Interstate H7. I believe others here had used the MTP-91, which is a bit smaller while the H7 was the right "size". Interstate checked their books and I looked and it did seem that the H7 was correct, but now you are making me wonder.

Tone

Update: Dealer confirmed after various checks the following:
H7 and 91 are same batts internally, but the casings are different sizes.
The 91 is a direct fir for the 996 chassis and the H7 is a direct fit for the 997. So the H7 is back in my car now. The H8 & 93 would be fine if you can get them to fit - more CCAs but larger & heavier.

Frino

P-dealer replaced my defective OEM battery with Interstate MTP-91 under warranty. No problems so far.

jhbrennan

Since the OEM 996 and 997 batteries are the same (same part number) not sure why an Interstate direct fit for a 996 wouldn't be a direct fit on a 997 and vice versa.

aviatorX

For clarification, having had them on the bench right next to each other, the H7 is IDENTICAL in size/shape to the stock Porsche battery for the 996 right down to the fold-down handles and the vent location. The -91 was NOT! Needed a vent kit, etc.

Also, the OEM battery for the 996 is listed as 380cca and the H7 is 640cca. Not sure why Interstate would say the H7 did not produce the specified cca's, unless they meant it was too much? How many cca's does the 997 require?

.

Tone

I'm sure on some of these details/answers...but from what I understand:
- 996 batt reqmts are lower than 997 (why? not sure, smaller engine/liters, less electronics?...this is based on Interstates spec sheet)
- Don't know how many CCAs the 997 require or what the stock porsche battery provides, but Interstate told me that the H7 & 91 produced less CCAs than the H8 & 93. Apparently the stock OEM battery has a history of very poor performance and this is why many dealers are dealing with non OEM replacements like Interstate.

jhbrennan

OEM batteries for 996 and 997 are the same.

jrgordonsenior

I've had a H6 for 2 years without issues. The car sits for a month at a time...