Another battery replacement thread...


FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
I was using an Optima Red Top, worst battery I've ever had, although many swear by it. I've had four or five years, and I had nothing but trouble during that time. Now it won't last for more than two days without being on the charger. Time to change it.

I'm looking at a Group 35 AGM which is about 9.5" by 6.75" by 7.75" high, and it absolutely fits in the bay... I did measure the tray spacing and it'll fit. The group 25, OEM batteries are about the same width and length but a bit higher. I don't see why I can't put a 35 AGM in there. I'm looking at the Canadian Tire Moto Master Eliminator, which compares to some of the best batteries out there. I've had good long term success with these in other vehicles.

This one is a 640 CCA, so about 90 CCA more than the original Ford battery, less than the "stated" spec of the Optima Red Top, which could be an arbitrary number for all I know. Anybody have any experience with the Group 35 fit? According to what I measured it should bolt right in.

If I read the battery dimension charts, which are easily available online, apparently the Group 35 and 25 batteries are identical in terms of size.
 
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2112

Blue/white 06'
Mark II Lifetime
I tried a group 35 Antigravity battery. The length and width were tight, but it fit.

It was 7/8" too tall and the frunk liner would not go in.
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
After reading your post, I went and measured the Optima Red Top I pulled out...it measures just shy of 8" in height to the top of the post.
Ford OEM is 8.75" for the Group 25. The battery I am getting is a Group 35 @7.76" height. The Anti-Gravity site liists the Group 35 @ 8.75", not sure why it didn't fit your GT. I wonder if the Group 35 posts are perhaps not in the same spot as the OEM, maybe sitting closer to the edge of the battery?
 

2112

Blue/white 06'
Mark II Lifetime
I am not at home to recheck, but I think, IIRC that the posts were not included in the official specifications.

But I will recheck that tonight. What I do know is that the frunk liner wouldn't go it. Happy to find out otherwise.

Which Group 35 are you using? Odyssey?
 

twobjshelbys

GT Owner
Jul 26, 2010
6,189
Las Vegas, NV
I believe Group 25 and Group 35 swap the posts... Most likely cables won't reach. It's possible the positive end might but the ground is quite short...
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
Yeah that exactly what it is. So turned my group 25 battery around to see if it would work the same as a group 35, and as 2112 posted above, it hits the bottom of the frunk.

The group 35 would have been nice because it's 200 CCA more than a group 25, but, OEM spec at Ford is a group 25 with 550 CCA and that's what I ended up buying today. It was under $200, and it fires up without a hitch. No need for the much bigger CCA capacity. This car will never see 0° in any case 🤪
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
I am not at home to recheck, but I think, IIRC that the posts were not included in the official specifications.

But I will recheck that tonight. What I do know is that the frunk liner wouldn't go it. Happy to find out otherwise.

Which Group 35 are you using? Odyssey?
You know, I've tried the Odyssey battery, and I've tried the Optima Red Top, and I have to say, they're overpriced pieces of junk, IMO. No better than a Delco but 2-3 times the price. The last Optima Red top in this car lasted less than a couple of years and I'd had problems since day one, as I had indicated above. I've been using Canadian Tire and Costco batteries, which would be the equivalent of an AutoZone battery in the US, and I actually have one of those suckers in a 48 KW generator outside my home, operating for seven or eight years. They're flawless and I live in Quebec, where it's brutally cold here all winter. But that battery just turns over that generator like nothing, a generator's powered by a 351 Ford V8 and is running on propane, which generally requires a substantially longer crank time than gas.

I remember my Gen IV Viper SRT had this huge battery to turn that big V10 over, and I had replaced the OEM battery 6 years in with a Canadian Tire battery, which was perfect until the day I sold the car 5 years later. And that is a hard car to start, with any battery.

I would have liked play with the antigravity battery, but they're horrendously expensive, I don't track the car, they're really the only ones who have those style batteries, and I can't find any reviews anywhere that indicate whether the battery is a half-decent battery or not. For a thousand bucks, that thing better add 150 horsepower to the car. Lol

So in all of my years with all of the vehicles I've ever had, and there have been a lot with a lot of battery changes over time, I'll just have to stick to the cheap batteries that get the job done. No more "high-end", overpriced batteries for me; just a complete waste of money.

I always go for the biggest and the best, but this just doesn't work.
 

2112

Blue/white 06'
Mark II Lifetime
The Antigravity is feather light and has the group 35 CCA. It’s just too tall by about 7/8".

I even considered having the battery box floor dropped to accommodate it, but put that on hold for now.

i think Optima and Odyssey were great 10, 15 20 years ago but now have gone cheap on the builds and are trading on their name recognition.
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
If you really want to put the anti-gravity group 35 battery in there, you could do it without dropping the holder floor.

You can easily get a battery extender kit for not a lot of money and spend about an hour extending the battery cable so that you can put in your group 35 battery backwards, and there you have it. It's not complicated and it's not difficult, just takes a little bit of patience and you'll have your cables extended without any downside. I've seen several kits, that function differently, and the one that I like most is this one...


It'll produce a nice clean splice which won't take away from the look of the OEM connection. If it's lightweight that you're looking for, then the only way you're going to get that is with the lithium battery and extending the cable. It didn't matter to me in my case because the group 25 battery gives me everything I need, and there's no advantage for me by putting in the group 35.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,281
Sorry you had a bad experience with the Optima Group 25. We have been installing a LOT of them. I'd say that on average we're seeing a minimum of 5-6 years of life from them when properly taken care of - either routinely driven or on a tender when sitting for extended periods.

They're readily available (around here O'rielly's always has them in stock) and obviously fitment is perfect. The fact that they're much lighter than most batteries is a plus too.
 
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FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
The fact is, they're heavier than most of the group 25 batteries. The group 25 I picked up yesterday which is the 550 CCA, weighs a good 7 lb less than the Optima red top. The battery that I picked up, tends to last me 5 to 7 years for the most part with no issue. It sits on a charger all winter and the odd time here and there in the summer when I'm not driving it for an extended period of time.
 

TO AWSUM

Ford GT Owner
Mark II Lifetime
Jul 4, 2007
1,512
Niceville FL
I've had my best luck with a Deka battery. Here's my post about it.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,281
The fact is, they're heavier than most of the group 25 batteries.
The Optima Group 25 is 31.7lbs... relatively light by automotive standards. Compared to traditional flooded Group 25 batteries which are 38-42 lbs, they're LIGHTER. Yes, there are definitely lighter batteries as you explore different chemistries.

$400,000-ish car needs a $250-ish battery every 5-6 years... a battery that is typically in stock locally and is a perfect fit and likely is the most popular/proven battery in the GT. A lot of noise here over nothing. If you're bored out of your mind and want to swap in flux capacitors, knock yourself out.
 

Brombear

GT Owner
Mark II Lifetime
May 16, 2013
1,405
Frankfurt Area, Germany
@nota4re

Can you Post the exact name of the battery ? Availability of certain models is complicated over here.
 

fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,680
Belleville, IL
He is speaking specifically about the red top Optima.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,281
Can you Post the exact name of the battery ? Availability of certain models is complicated over here.
Yeah, Optima RedTop Group 25. You can click on this link to see it on their website. REDTOP 25

Note that it is the OEM battery that all GT's came with....
 
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twobjshelbys

GT Owner
Jul 26, 2010
6,189
Las Vegas, NV
Available at most auto supply stores like O'Reillys and auto zone for about half of what Ford charges for theirs after applying the sticker
 

Brombear

GT Owner
Mark II Lifetime
May 16, 2013
1,405
Frankfurt Area, Germany
No O‘Reillys nor Autozone over here :devilish: Have to rely on online shopping or going to a Ford dealership (and having to wait).
 

fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,680
Belleville, IL
I would think that GT 101 would have access or knowledge concerning this brand/battery.
 

2112

Blue/white 06'
Mark II Lifetime
Available at most auto supply stores like O'Reillys and auto zone for about half of what Ford charges for theirs after applying the sticker

and often in stock.