[Qmulus]

I think that you will find that any of the lightweight batteries will have trade-offs. It comes down to what trade-offs you are willing to accept. I think that you will find AGMs, like your Odyssey, can often be damaged if you run them flat to the point where they do not recover. That is why it is crucial to keep a battery maintainer on them. The good part is that they work well in the cold as well as warm weather.

The Antigravity battery that you mention is a Lithium Ion, basically made of the same type of batteries most electric cars are going to, like Teslas. There are a few issues with lithium ion batteries. First, they do not tolerate overcharging whatsoever, that is why the Antigravity batteries have built-in battery management to handle this. Without it, bad things could happen. They also lose a fair amount of CCA in the cold, so they aren't great for a daily driver, unless you live in a very temperate climate (ah, Sweden, I don't think so...). These batteries also can be damaged by super high discharge rate, so if you short the output, even momentarily, you can damage cells.

There are also lithium iron phosphate batteries, like those from Shorai, which I have some experience with as a local shop that races Porsches uses. Lithium iron phosphate batteries are good because they take really high charge rates, tolerate overcharging (so they are inherently safer than lithium ion) as automotive systems run at a higher charge voltage than three fully charged lithium iron phosphate cells, and have high discharge capacity. There are issues though, as they have the same cold weather issues and can also be damaged if they are shorted. Then they are pretty much junk. The Shorai batteries also SHOULD be used with a specific charger that balances the cells, and is required (IMO) if it gets severely discharged. I have had to "restore" a few of these batteries by charging individual cells. The nice thing is that these batteries have a connector made for the specific cell balancing charger that gives access to individual cells. These batteries are good when lightweight is the highest priority, but are not something you just install and forget.

My $.02: I would stay with a traditional lead acid battery unless you are really serious about saving weight and disconnect the battery when it sits for more than a few days. Any lightweight battery will have trade-offs, no matter what the manufacturer claims. In general, you are trading capacity for weight, which is not an issue in powersports applications like motorcycles, etc., which do not have constant loads applied like street cars do. In street cars, you have constant loads that while very small (like 30mA or less) WILL discharge a lightweight battery much faster than a big old lead acid. On a daily driver, sometimes DE/track car I think the trade-offs of going to a lightweight battery aren't worth it. The PITA of having to fish for the frunk release cable just once is enough that I wouldn't do it. I have MUCH better things to spend my money on.

P.S. For BrandyB, the stereo or amplifier doesn't affect the battery unless you are running the stereo with the car off. So, no, the stereo is not an issue when it comes to lightweight batteries.