Interstate Battery replacement

[Iciclehead]

No major drama here, just thought I would post the Interstate battery number that fits my '75 911 using the factory locators. Turns out the one they normally list in the Interstate fitment guide is not quite right - the local Interstate guy spent a few minutes checking and it turns out that the correct, factory fitment Interstate equivalent to the Genuine Porsche battery is Interstate MTP - 48/H6.

This is the shorter of the two batteries that we can use in 911's, it uses the stock clamp and the closer of the two captive nuts on the floor of the battery tray.

I had been using only Porsche batteries, finally went through my 3rd in about 7 years when I said "Enough!" and went looking for an alternative. Major difference in warranty, Porsche (in Canada) only gives a 2 year warranty (replacement only in the first year) and appear to decline coverage if the car has been stored and not run for extended periods of time (say 5 months) unless a Porsche battery maintainer is installed. I have replaced the alternator/regulator, checked out for current draw and all that stuff and there are no issues that I can find with the electrical system. I also always disconnect the ground when the car is in storage in a heated/enclosed parking garage.

Interstate gives 6 years warranty, 3 years with full replacement and the remaining pro-rata and no questions asked about storage or whatever. In fact the Interstate rep, an older very knowlegeable gentleman, said to make sure to bring it to him if it did fail and he would find out the failure mode to see if it really is storage that is giving me grief.

Price was not too horrible, $207 plus tax here in Calgary.

Dennis

[ClickClickBoom]

Use a battery tender, without one I am surprised the batteries lasted that long. My first battery on my CB1000 lasted 11 years, and was only ridden 7 months a year. Had a tender on whenever it wasn't being ridden. Lead acid batteries have a self discharge rate, and when cold the margins between charged and dead is smaller.

[wwest]

Costco, <$100.

I just turned in, $9.00 core, 08 Costco purchase, 5 years of service, no float charger.

[brads911sc]

the need for a float charger, or not... is determined by your situation... how much you drive vs not drive and other environmental factors... not where you bought your battery. 95% of the batteries manufactured are made by the same two companies... all will need a float charger if the car is sitting months at a time to preserve longevity.

Originally Posted by wwest

Costco, <$100.

I just turned in, $9.00 core, 08 Costco purchase, 5 years of service, no float charger.

[Iciclehead]

Ok, what does one do when there is no electrical outlet near the spot where the car is stored? I know I could pull the battery, but would a periodic charge (e.g. put it on a charger for a couple of hours every month) do the trick or is the continuous full charge that is the trick?

I find it a bit interesting as years ago when I had just finished restoring the car, I used the larger battery (the one that is the same as a Mercedes diesel), stored it in the same manner without a charger and it lasted for years....I think 6 or 7. It has only been since I switched to the smaller one - Porsche - that there has been an issue.

Also, do those two major battery builders build to different specs in the same physical size or really is all we are looking at is which pretty label appeals to us the most.

Oh yes, I have no doubt I could find one at Costco, but I suspect prices are higher here in the far north plus I am actually willing to pay for the service the guy gave.

Dennis

[john walker's workshop]

MTP-91 is the normal one for that year. the larger MTP-93 will fit also.

[a&j]

Originally Posted by wwest

Costco, <$100.

I just turned in, $9.00 core, 08 Costco purchase, 5 years of service, no float charger.

Which brand/model? Would help if you would be more specific... Interstate? Optima? Kirkland?

did it include the hotdog + soda? Or was it just the smoothie jk

[Jagshund]

Interstate also sells blems (sometimes rebuilds); my current unit was $30. I'm not sure about the contact up in your area but down here there's an 800#. So far, in my experience, performance & warranties have been the same but I believe you must order through someone with an account.

[Iciclehead]

Originally Posted by john walker's workshop

MTP-91 is the normal one for that year. the larger MTP-93 will fit also.

There appears to be more than one that fits. Thing I like about the one I got is that it is dimensionally exactly the same as the Porsche battery, right down to the shape of the holding lugs on the bottom of the battery. Since I haven't seen an MTP-93 (and I don't recall that number in the discussion with the Interstate guy) I can't comment where or even if there are dimensional or capacity differences.

Dennis

[Larrybrook]

I bought mine at Canadian Tire $85.00? I made an adapter and it's worked fine for years.