I need to free up some more room in the trunk well after removing the bins and panels. Anyone had any success with a smaller battery. Lithium or similar?

 

The size of the lithiums is not sufficiently smaller (maybe 30%) to justify the expenditure for trunk space savings. Besides, you'd have the remove the boot floor to take advantage of that space and that would leave electrical wiring and connections exposed to potential damage or disturbance.

 

Don’t worry about all that Mr Unhingd. I made plenty of space for my sub with my last f type by moving parts around etc. Just could do with a bit more on the new f type hence the question about the battery. 30% could be good but I have no idea whether the battery itself does the job.

 

I have the 24Ah Antigravity H5/Group-47 lithium battery, which is a bit shorter than the original one. I suspect physically smaller batteries with similar CCA and capacity work just fine too, but the Hn batteries fit the OEM tray nicely. Don't forget to do a BMS reset after swapping batteries to avoid charging issues though!