Another battery question Interstate vs Miata

[Quickstep192]

Last time I replaced batteries, I used AGM Miata batteries. I liked that they wouldn't leak, but I never liked the fit and the positive terminal was uncomfortably close to touching the top of the battery box. The only thing seperating it was a rubber boot. If that boot had worn through from rubbing, it would have made for quite a fireworks show.

Now I'm considering the Interstate U911 that's supposed to be a perfect fit and has covers for the terminals to eliminiate contact by the positive terminal. I think it's a sealed lead acid battery. Does anyone know if it truly is sealed? If so, does that eliminate the age old problem of corroded battery boxes?

[GH85Carrera]

I have the GIANT Interstate battery. It has a drain tube to drain excess acid. You can get a battery mat that neutralizes acid to put under the battery. I check my battery every few months. No problems after 18 years of using the same type battery. They often last 5 full years and I replace them just because they are 60 months old.

I keep the GIANT battery for the reserve power. One time I left my dome light on overnight. The car fired up with no problem. It is heavy and bulky but the Porsche engineers put it there for a reason.

[grizzfan]

I recently purchased two Interstate U911 batteries for my '73 911T. They fit just fine although one of the terminal covers binds just a little bit against the top of the battery box. It's lead-acid but cannot comment on whether it's 'sealed' or not. I didn't see the aperture for a drain tube on the batteries but will look soon as I'm doing some maintenance in that area.

They are pretty powerful batteries as I put my Porsche to bed in early November with the two installed and no trickle charger over the winter. Fired right up in early March after one of the coldest winters in Montana in a decade or two.

Tom

[LJ851]

Originally Posted by GH85Carrera

I have the GIANT Interstate battery. It has a drain tube to drain excess acid.

The vent tube is not there to drain acid. When a battery is charged and discharged, hydrogen and oxygen are created and vent from the battery. On a vehicle like a 911 where the battery is in an (A) an enclosed space and (B) connected to the interior, this is a dangerous situation.

The vent tube allows the gasses to be routed safely to the exterior of the vehicle. You won't see a vent tube type battery in the engine bay of a vehicle since it does not have this situation.

[Reiver]

Why not an Optima red top.....had one in the SC for 2 years now and it spins it fine. I've had them last 6 years.

[Quickstep192]

My car is a '73 with the dual battery setup. I want to keep the original configuration. Best I can tell, it comes down to the Interstate Batteries, Miata Batteries a Sonnenschein Battery (which I can't find a place to buy) or OEM.

[cmcfaul]

The easiest solution is to take the car to a Battery Plus or some other place that has a large selection. Measure the batteries on desplay and buy the ones that fit the best.

I have been down the U911, Sesquation (spelled wrong) and Miata route, though I never bought the Miata's. Ended up with the ones that simply fit the best. This has resulted in the best battery choice thus far. Not sure why but the U911's and the Sequation's (gell type) did not last very long.

The ones I have in there now are about 5 years old and no problems ever. They do have the vent tubes and think I had to make them a bit longer to reach the holes in the floor pan (infront of the spare tire), but no big deal at all.

Thats my recommendation.

Chris
73 911 E

[HarryD]

I installed a single red top optima in my '73. Put it in sideways, no problems. If you search on my handle, you will find a picture.

I replaced a dual set of Interstates that I was tired of pulling twice a year to neutralize the acid residue and repaint the boxes.

[Quickstep192]

I'm interested in expert opinions on this battery I just found. It's supposed to be a replacement for the Sonnenschein A512/40. It fits and can use post terminals or bolt terminals. The guy at the battery store said it might not do well as a cranking battery since its intended use is as a deep cycle for UPS. What do y'all think?

http://www.interstatebatteries.com/cs_eStore/Content.aspx?dsNav=Ntk~SearchGroup%7cSla0190%7c3%7 c,Arpp~12,A~Part+Number,N~44-2147384903,Nr~AND(P_unique_id%3aLintronics+MX12400 +SLA0190)

[gamin]

Just removed the old U911 batteries from the 70 and replaced them with Westco Miata batteries. The Interstate U911 batteries are NOT sealed. Regular removal and acid cleaning and painting was required. Believe it or not, the car seems to start much better. I'm done with leaky batteries.

[Quickstep192]

Originally Posted by gamin

Just removed the old U911 batteries from the 70 and replaced them with Westco Miata batteries. The Interstate U911 batteries are NOT sealed. Regular removal and acid cleaning and painting was required. Believe it or not, the car seems to start much better. I'm done with leaky batteries.

What did you to to ensure the positive terminal couldn't contact the top of the battery box?

[Series900]

I had the same dilemma. I went with optima in the 69 race car mounted in the right box, because racecar! no spare tire... The optima can work in the left box for street if you do not have a charcoal canister. made an extension strap to maintain the factory latch holdown in either case.
However, I had to install a new battery in a 72 street car, full size spare tire and charcoal canister. Went with the odyessyPC925 sealed AGM with sae posts from sepbatteries dot com at $153 and free shipping. I had a pair of factory dead lead acid batteries, side by side, I cut a 2 x 10 to match the height and width, notched around the posts and no modification to the factory latching and no movement or worry over potential shorting.

[E Sully]

I am with gamin on this. I have used the Westco Miata batteries since 2008, and am a firm believer in the agm batteries. They also worked great with the larger 3.2 engine when I had it in the car. I am sure my new suspension pan and battery boxes will be much happier. I don't mind a little shimming in the battery boxes to make them snug.

[cmcfaul]

The Sonnenschein batteries fit perfectly but are wheel chair batteries. Expensive and mine did not last long.

Chris
73 911 E

[p911dad]

I have had a total of 3 Interstates in our 84 Carrera since we bought it back in 91'. The current one has been in since 2005 and still tests fine. No leakage ever, and I always have had the vent line in place. I have the acid mat under the battery just in case of leakage. The only maintenance issue has been the green fuzzy stuff that occasionally has to be removed from the terminals. I am planning on another when this one expires. I haven't really seen any issue that would cause me to put a non standard replacement in, and since we don't compete there is no weight issue (it is heavy, no doubt about that).

[nineball]

i can see no good reason to used old technology (lead-acid) when there is a vastly superior option available today (agm). it's like that infomercial - set it and forget it!

interesting side note... the interstate website has a banner proclaiming a 25% off and free shipping deal using code TAX14, valid through 4-16, but the fine print states "not applicable on automotive, motorcycle and marine/rv batteries". so i guess if you really need a new lawnmower battery you are in luck!

[BSNMOE]

Originally Posted by gamin

Just removed the old U911 batteries from the 70 and replaced them with Westco Miata batteries. The Interstate U911 batteries are NOT sealed. Regular removal and acid cleaning and painting was required. Believe it or not, the car seems to start much better. I'm done with leaky batteries.

I believe the Miata Batteries have more CCA than the U911. That will give you better starts.

[dicklague]

I have been running miata batteries for years... at least 10, and they are great! I have friend with an auto parts store' and the price is right too. I use a wooden block behind to move the terminals forward and away from the metal.

[tcj911t]

My Interstate U911 batteries needed to be replaced this spring (after 9 years) and I decided to try the Miata AGM batteries recommended in this thread as a replacement this time. I ended up purchasing (2) Marathon AGM Miata batteries from Battery Mart for $99/each (with free shipping) vs. the $150/each for the U911s (including tax). My understanding is that these batteries are the same as several others re-branded on the internet made by East Penn and are generally recommended highly. The batteries are lighter than the Interstate batteries (24 lbs vs 27 lbs) and are slightly different dimensions and need to be fitted a bit. I added some pictures of the Marathon batteries compared to the Interstate batteries and pics of how I installed them in my 911T. I ended up adding a wood block to the back of the battery boxes and then added some plastic shielding to the positive terminal to protect against shorting to the metal. Some other observations I had on the install are:

* The Marathon batteries fit in my 911 battery boxes without needing any modification to the box. The height is a little tight, but not too bad with some plastic or rubber shielding.

* The area around the terminals is tighter that the U911's and I needed to buy a new positive terminal clamp for my right side battery and turn the negative terminal clamps 90 degrees to get them to fit. I am not sure why they limited the room behind the terminals?

[SCadaddle]

I just replaced the Miata battery in......well.......my 1992 Miata of course! It fits in the trunk and has a pair of slip on vent tubes that connect at a T then a single tube out the bottom of the trunk. That's why you are seeing a pair of vent taps on that battery in the photo above.