bean438

I would like to replace the oem battery with an Optima red top model.
Local dealers would simply replace the oem with the same spec replacement according to their books.
I know that there is a DYI on the 75/35 battery instal, and someone also put in a 34r battery.
I am a little confused as to what to buy. Optima supposedly now sells a group 35 battery.
What does all this mean?
Is a group 35 the oem size?
If the 73/35, and 34r will both fit then why bother with the group 35?
I thought that group numbers corresponded to physical size and that only one size would fit.
The 75/35 requires an adapter. I dont believe the 34r requires one, and I believe the group 35 should just drop right in.
The 75/35 is available locally off the shelf while the 35, and 34r would have to be special ordered.
Is there any advantages/disadvantages to using any of these sizes?

bean438

I just checked out this site:

http://www.gglotus.org/ggtech/batter...y-bci-size.htm

They list the 35, 34, 34r, and 75, but not the 75/35.
What is a 75/35 battery then?

rx8cited

Don't mess with the 75/35 which will require an adapter.

If I had to buy a battery today, it would be a group 35 which is the largest battery I know of that will fit the RX-8 battery compartment and not require any mods or bad adapters. I'd like to know what brand/model you end up buying and how you like it.

Again, don't even think about the 75/35 :D.

Go48

The "new" replacement battery for the RX-8 is rated at 640CCA versus the 300+CCA original battery. Might want to look into that instead of an Optima. Have read mixed reviews of the Optima from various sources and on various forums.

PHA RX-8

Go with the size 35 battery. I ordered the 35 battery for my car. They called yesterday and told me it was in. Once i get my car back from the dealerer (I flooded it) I will have it installed. The service advisor wasn't enthused by the 640CCA battery replacement and was happy to see I odered a optima red top.

rx8cited

bean438,

If possible, could you give me the dimensions of your stock Canadian RX-8 battery please? The width and length measurements would be great if you cannot measure the depth.

FWIW, I think Optimas are overrated due to their hi cost and personally would not spend the money on one based on my limited battery research.

rx8cited

PHA RX-8

I paid $99.99 from Batteries Plus and they are installing it.

bean438

The battery dimensions are:
7 3/4 H
6 5/8 D
9 W

There is nothing on the battery about CCA's, etc. Only some Japanese writing.
The battery is tight depth wise but there is 1 1/4 " room left width wise for a larger battery.
However if the 1 1/4 is covered up it will cover what appears to be a hole for air circulation.
With the Optima 75/35 you use the height adaptor which seems like it would allow the air flow.
I dont know how big a deal the air flow is for the battery compartment is but Mazda would not have a TSB on it if it was trivial.
So, I guess the 35 would be the best choice.
Problem is that all local dealers would replace my Mazda 525 CCA battery with a different brand 525 CCA battery, thus the look at the Optima line up.
They supposedly now have a 35 direct replacement battery but I cant find one on their web site.
Honestly you are the first to say anything bad about Optima batteries. I have read nothing but good things. I find if a brand comes up over and over again good or bad, there is a reaqson for it.
You base this simply on the high cost, which I agree with, but the Optima 75/35 is priced at 121 CDN which is on par with most "premium" batteries available locally.
My deal is I need it to fit properly and I need more CCA's for our cold winters.
I trickle charge at home but I cant trickle charge everywhere.

Brava41

Go to remybattery.com the 35-910 optima red top is the right replacement. It's dimensions are: 9 5/16"L 6 13/16"W 7 5/8"H and is rated at 720 CCA and 910 CA.
I have ordered one and it is in transit should have it on Friday.

salituro64

What replacment battery? And 300 to 640 is more than double the power, could Mazda have miscalculated the cold impact that much?

Go48

Uh huh. Why does that surprise you?

Check out the TSB at the following link:

http://www.finishlineperformance.com.../01-042-04.htm

Go48

The length dimension of that battery is about 1.25" longer than the original battery. See the following TSB for information on the "new" OEM replacement battery and the importance of preserving the air space around the battery.

http://www.finishlineperformance.com.../01-042-04.htm

beachdog

I'd make sure to preserve the airflow. That's not just a vent, it leads into an air intake right behind the grill.

Consumer Reports has not given top grades to the Optimas. They do well, but others rank better.

rx8cited

I don't think you'd go wrong with buying an Optima, so go for it. IIRC Consumer Reports felt that they were overrated for their price and has not even bothered testing them in the last few years.

Here's a place that sells the Optima Red Top group 35 for $94.95 shipping included (not sure if that includes Canada).
http://www.batteriesareus.com/shop/p...products_id=61

If you look at bottom of the battery TSB, you'll see xxxMT35xxx, which I assume is a group 35 battery, so I'm guessing there would be sufficient air flow room for a group 35 battery.

Also, if you want to buy your Optima locally, look in the yellow pages for battery distributors and call them. They should be able to get you the Red Top group 35 if they don't have it in stock.

rx8cited

PS: Thanks for the dimensions. My US stock battery measures 6 5/8" W x 7 3/4" L x 8" H (8 3/4" H including the post). I though the Canadian battery might be larger, but it seems that's not the case.

mitchfried

So the Optima Red Group 35 is too long (covers the vent hole?)

How about DieHard replacements?

Brava41

The replacement battery in the tsb is a 35 battery, the tsb points out that the larger battery must be properly positioned in the battery box so as not to block the intake duct the box is 10.25" long, the optima is 9.0" at the base and does not block the air duct if positioned according to the tsb. The oem battery is centered in the box, the 35 battery, whatever brand is used must be positioned against the rear of the box and then will not extend past the white paint mark and will allow airflow into the box.

RX-Nut

So would you all agree the Optima 35-910 is the best replacement over the OEM battery? Powerwise, reliability, fit, etc?

Go48

I agree that you can squeeze a longer battery into the stock box. However, I just measured the OEM battery and the box, and in my opinion, with a battery any longer than ~8.75 inches long, you will be blocking most of the front lower air duct. And that's with the battery installed all the way to the rear of the box as you say. IMHO, 9" is just a bit too long. It will certainly fit in the box, but it will at least partially block the air duct.

A couple of other observations. The width and design of the battery box is such that you MUST stick with the same width, ~6.75", in order for a battery to fit. In addition, the height of the battery should be the same, ~8", in order for the hold-down bracket to fit. Obviously you can place a spacer below the battery to bring it up to that height so this dimension is not critical.

Personally, if I was going to replace my OEM battery, and I'm not, I would look at the more-robust OEM replacement battery mentioned in the TSB first before going for another brand.

rx8cited

The Optima Red Top 35 is not 9" long.

From the web links previously posted, it is
Length : 9 5/16" Width : 6 13/16" Height : 7 5/8".

I'm just pointing out this 5/16" difference as there's valid concern here about blocking the vent.

If anyone installs the Red Top 35, please post a picture so we can see where the battery front edge is relative to the white line mentioned in the TSB.

rx8cited

Go48

Here's another option for a replacement battery. It's not as "elegant" a solution as the famed Optima Red Top, but it will fit in the battery box, the battery posts have the correct orientation, and best of all it's inexpensive.

Exide part number 26R-60
60-month warranty
maintenance free
525CCA
630CA
L-8 5/8"
W-6 3/4"
H-7 15/16"
Cost~$50

May need a spacer to raise the battery to the proper height, but that shouldn't be a big deal. I suspect that finding this model in stock at a local retailer might be a problem since the battery post orientation is apparently not the norm for most cars. I'm sure it could be ordered, however. Exide batteries are available at Wal-Mart, K-Mart, and CT Farm & Country.

Gomez

Bean, I'm not sure I'd be too worried about creeping over the white line with your replacement battery. In your cooler climate the underhood temps aren't going to be sky high. You're not going to be affecting your warranty either.....

Gomez.

Go48

Here's a very interesting response I received from an inquiry I made to Trussville re: the "new" replacement battery:

"Larry,

First let me say that we can not ship these batteries because of the HAZ-Mat classification.

The list price is $123.90.

As far as the CCA we seem to have conflicting information here. We have two of these in stock, and the CCA listed on the batteries is 550 CCA I have sent Mazda an enquiry regarding this and hope to hear back from them tomorrow.

As far as the measurements on this battery, it is 7 inches in width, 9 inches in length, and 8 inches tall. We order our batteries from Mazda and they are drop shipped from Interstate batteries. Usually the batteries have Mazda labels on them, however these new batteries have Interstate labels on them. I will try to let you know what Mazda has to say about the CCA'S when I hear back from them."

I suspect that the measurements provided are approximate, because the 7" width would be a very tight fit in the battery box. Another thing is, since this is an Interstate battery, it would probably be smart to purchase one locally from an Interstate dealer.

EDIT: A check of Interstate battery specs indicates that this model is part #MT-35.

L-9"
W-6.88"
H-8.75"
550CCA
690CA
Termination A (?)
Orientation of posts not clear
List price-$84
Suggested price-$70

EDIT #2: A further check of Interstate batteries shows a model part #MTP-35 that has the same physical dimensions as the above battery, but with the following differences:

640CCA
800CA
List price-$89
Suggested price-$75

I suspect that Mazda is confusing the two batteries in the TSB. Their part number contains "MT-35", but the CCA rating is for the MTP-35. So I guess it would be advisable to purchase the latter battery since it is the same size with greater capability and only $5 more.

That's all folks!!

RX-Nut

interesting.. please let us know what Trussville gets from Mazda later..

Go48

Don't expect to hear back 'til at least tommorrow, but will definitely post whatever they say.

Brava41

his top-view drawing illustrates post placement on the Optima Model 35 battery.
Note orientation of positive and negative posts.
Model 35 top dimensions are 6.3"W x 9.25"L. Height is 7.8" including posts. Case height w/o posts is 6.8".
Base measures 6.7"W x 9 "L.

The spec's for optima batteries can be found at: 1st-optima-batteries.com.

Notice the base is a bit shorter and wider then the top.