UnderdogI've been running a tiny 6-pound battery for about 2 years now. You can read about that here: Lightweight Battery Project.
The YTZ10S battery that I've been using is about an 8AH battery with 120CCA.
For reference, the OE battery is a closer to 50AH and 350CCA.
This little battery has been reliably starting the car for almost 2 years. Well, that's not quite true. The first battery failed due to an OBD2 device drawing current when the car was off. Repeatedly discharging it to nothing didn't do it any favors. So, the current battery went in back in 11/2019. So, it's been about a year for THIS battery, and 2 years of using this size of battery. It does seem a little sluggish starting if I let it set for more than a week, and I have had to jump it once or twice due to that. (COVID has had me in a state of not driving my cars much) The cheap battery that I bought also seems to have a slight leak, and it showing some corrosion on the tie-down bracket. Otherwise, for a $30 battery that weighs almost nothing, I can't complain too much.
For my purposes, if I were closer to "daily driving" the car, it would be adequate. Bear in mind that I live in Florida where 50 degrees is considered downright frigid.
But, now I've quit autocrossing the car, so "ultimate light weight for performance" is less of a concern. And I've started getting more into hypermiling the car, and engine-off coasting a lot... and I want to be able to reliably restart the car for many more cycles while I'm driving it. So, I need more battery capacity. I don't think I need a full 34 pounds of OE battery capacity, but more than I have would be nice.
I think I've settled on a nice YTX30L motorcycle battery. It weighs just under 20 pounds. (14 pounds more than the itty-bitty battery, but still 14 pounds lighter than stock) The price is a low $55. 30AH capacity, 385CCA. Not bad.
I still might change my mind and go with a bigger, possibly deep-cycle battery. Hypermiling is a harsh mistress.
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