Some years ago I acquired a Canon EOS 7D DSLR, primarily for wildlife photography. I always fancied a shutter release in the portrait orientation so I bought a battery grip for it. That takes two batteries so, instead of lashing out on an expensive Canon original battery, I got two pattern batteries by Hahnel. They don’t have quite the same amp hours as the Canon LP-E6 but they are fine, especially as back-up. My 7D charger charged them and all was well.
When the EOS 7D mkII was introduced, wanting the built in GPS (for wildlife recording) and somewhat improved high ISO noise performance, I upgraded.
The first thing I noticed was that Canon has cunningly changed the position of the locating lug on the battery grip so my 7D mkI battery grip does not fit the 7D mkII. Nice one, Canon!
A further surprise was in store. The charger that came with the 7D mkII, whilst being ostensibly the same as the mkI’s charger, refused steadfastly to charge my pattern Hahnel batteries. Thanks a bunch! I continued to charge them in the original 7D mkI charger so I continued carrying them around as spares for the 7D mkII. When I eventually tried to use the Hahnels in the mkII camera, things got worse; the 7D mkII camera body refuses to run with one of the Hahnel batteries installed.
This doesn’t seem to be a compatibility problem between the LP-E6 compared to the newer and more powerful LP-E6N (introduced at the 7D mkII) because the 7D mkII works with my genuine Canon LP-E6 battery from the 7D mkI. No, this bloody camera seems to be detecting a “foreign” compatible battery and rejecting it. It appears to be forcing the use of genuine Canon batteries.