These is a way to make your dead batteries survive one or two times.
Dead batteries mean that they died by being too much discharged.
If you use all capacity and leave it and forget for one week or something, it will be totally died.
Please refer to attached article file from BATTERIES IN A PORTABLE WORLD,
v mount battery has serial 4 cells, so its dead voltage will be 4 x 2V = 8V.
Please find the method, how to make it survive, but it is only one or two times.
It happens sometimes by your customers, so please warn them first and repair the batteries if it happens.
When you receive the batteries, they will last over 6 months without first charging.