@johnf3f whilst I disagree with you that the Canon LP-E6N are junk, using decent NiMH AAs in the battery grip, however, is a great idea, which I will definitely be trying.
I have a few dozen Energiser Extreme 2300s which I use in my speed lights, and are pretty good.
A pack of four of these are around 12 quid, three packs being 36 quid (always good to have a backup set), which is about the same as one standard Hahnel battery!
Not sure if the OP has a battery grip.... they're eye-wateringly expensive for the 7DmkII, at around £250 new!!
I felt fortunate to find a decent condition used one, combined with a 'one day 10% off all used gear' special offer, for £100, from Wex.
Still a bit steep, but it's never off my camera....easily the best hundred quid I ever spent!
I bought a number of LP-E6/N packs for my camera and they are all junk including the one that came with it. On the other hand the rather old Eneloop 1900 Mah cells that I had lying about for several years perform excellently. They give lots of shooting, self discharge is irrelevant (unlike the Lithium packs!) and are simple/easy/quick to charge.
How many shots do you get from these batteries?
Is your grip a genuine Canon or an aftermarket? as some are known to have battery drain issues.
I managed to take over 2600 shots at Flying Legends using 1 original Canon battery & 1 ExPro which still had 50% left - (not using grip)
The reason I asked is that I have just bought a Canon BG-E16 grip but not used it yet, and from your comments I think I will buy a set of rechargeable AA's as a backup.