Apologies that I don't have better information for you, but this may help-
I'm not fully sure how long my arrangement will run. I have run the F8 for around 12hrs in the past on the 11,000 mah Talentcell, years ago. Draw included phantom on all 8 channels, powering one DPA XLR adapter and 6 PFAs converters providing low voltage power to miniature DPAs, + one phantom powered Naiant X8, but not sure what that equates to using more typical SDCs.
That said, I'd not feel comfortable if I needed to run that long constantly without a backup battery in parallel or to swap over to, or at least through testing first. I've only run that combo with the single external all the way down to shut-off a couple times by accident after the battery was partly depleted [note that the F8 switches off when there is still one light lit on the Talentcell's meter if there are no backup internal batteries or other external supply], yet have never done so over the course of a single extended session. I originally set up the F8 with a "Y" splitter in the external battery cable so I could swap from one Talentcell to the other and/or use both in parallel simultaneously for long duration events such as full day fests, primarily because that was how I had previous recorders set up for use with much smaller capacity "DVD batteries" that the Talentcells replaced. However, in practice I've never actually needed to swap from one to the other during the course of a festival day. I instead either simply recharge the Talentcell I had been using overnight before the next day, and/or switch to using the other one the following day. Granted, even prior to moving to the F8 I generally tended to no longer record every act, nor leave the recorder running constantly all day at a fest, but shut it down to conserve power as long as I'm around to do so whenever music was being performed at other stages. The last I recorded afternoon into evening and just left the F8 on the entire time, recording for the majority of that time (phantom on the entire time), was a small fest last December where I ran for something like eight hours or so, after which the battery meter indicated it was only around half-depleted. Although in reality it was probably somewhat more than half depleted given the previously mentioned "shut down before the final light goes out" behavior.
All in all, if you plan to record for 12hrs straight I'd think a 11,000 mah battery is likely the bare minimum, which can work fine in combination with with backup internals and a spare external you can swap over to. A "Y" power cable is extra insurance for the external battery swap, in case the backup internals have lost charge or are missing.
Last I looked a few years back, Talentcell offered a few different capacities in each case size. In other words, there was a thick and a thin "brick" case size but maybe four or more capacities depending on how many cells were inside. At the time the 11,000 mah one was the largest capacity offered in the larger brick size. I considered picking up whatever the largest capacity was in the smaller case size as that would certainly be adequate for most concerts, but have just used these.
