PS VITA : Battery setup for storage

I have read following thread about PS Vita battery : https://gbatemp.net/threads/ps-vita-3g-battery-drains-quickly.537421/

That made me think about battery setup for medium or long-time storage.
I have read that a good idea would be to have the battery at around 50% when storing the unit for several months.

I recently got a unit that must have been stored for some time, and the battery would just not work anymore even when charged : I did a complete charge/drain cycle, and then the battery would just die at around 60%. Maybe it was just too old (836 cycles, so it was used but could have lasted until 1500 cycles, well I hoped). I don't know how it was stored, or setup for storage.

So I was wondering if anyone had experience in storing Vitas, and getting the unit to work ok after some time.

I also imagined it would be possible to unplug the battery from inside the unit, after charging to 50% : has anyone tried this?