I don't see how the CF makes much of a difference here. Most batteries have their cases made of polyprop, which isn't exactly heavy. CF is stronger, sure, but that's more for looks than functionality IMO. Even if the CF saves some weight it can't be that much weight savings v. polyprop.
Braille battery seems to be pretty similar to the Kinetix batts they use in car audio circles (minus the CF of course)...
We commonly use these on race cars, where 20 pounds is a serious weight savings, and the compact size allows flexible location ( like the smuggler's box in early Porsche 911's). They work great; keep it on a tender, don't overload or abuse it, - cranks every time. I've seen them installed on daily drivers, but they require some care and planning. I wouldn't want to rely on this to crank a v8 that's been sitting outside for two weeks in sub-freezing weather.
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