@stealthsculler

Covering the middle terminal is not something I tried with the 3rd party batteries that I had (now all returned). I assumed that those had a middle terminal that was not connected to anything as the two 3rd party chargers I bought for this battery did not even have a middle connector.

I have just repeated your experiment with two original Samsung IA-BP85ST batteries in my VP-HMX20C (i.e. UK model). I can categorically state that covering the middle terminal or either of the of the outer terminals produces identical results - as if there were NO battery there at all. I could not power on.

Curiouser and curiouser …

It does make sound business sense to make every battery unique to a particular device with chips that are not easily reverse-engineered. I would have said _short-term_ business sense but Microsoft is the empire it is because of the 'incompatibility' business model. The most annoying aspect is that there are thousands of eBay sellers who mis-sell 3rd party batteries and there is no adequate recourse. I wrote an eBay guide based on my original post above. It was more measured, formal and referenced. It was published and then removed around 2 days later I can only assume on the request of of one or more of their big sellers.

Best of luck and keep the community informed, as will I.

Tim.