i tried doing a search on this and came up empty so I wanted to check with the group.

i searched for batteries on auto parts stores and they don’t specify the convertible so I’m unsure if they share the same battery. Some say get the AGM, others say don’t. Some do have the convertible and don’t use the AGM (O’reilly & AdvancedAuto). Knowing that the roof requires heavy battery use and reserve, my first thought is to get the AGM battery (typically around $200-$280 for top of the line aftermarket).

Im not trying to skimp (just not spend $600 at Lexus). Are the AGM batteries too much juice?

some recommend “group 34” others “24”. That has me more puzzled.

So what is the forum using? Any problems?

I have a 2011 IS250c

Thanks all for the suggestions. I did notice the Interstate batter from Costco (group 24) at under $100 so had to double check if it would work and work well. Sweet.

While your engine is running, your alternator is providing all the power that your convertible needs for all functions, not your battery. Your battery is only used for starting your engine and for providing power for radio, lights, etc. for a minimal amount of time with the engine off. If you open and close your roof without the engine running, then you’re just asking for trouble battery-wise. Always run your engine while operating the roof and you’ll never run down your battery. That being said, the battery for you is no different than the battery for a non-convertible IS. If you search on Advance Auto Parts for example, the battery search results are the same whether you search for IS or IS-C.
Happy motoring!