This goes for any multi cell battery, will not make any difference on single cells. It also depends on the what the charger does when it detects a cell becoming fully charged...but generally.
In a multi cell battery pack, one cell will always reach full charge first. This will cause the charge current to reduce. leaving some cells under charged.
Disconnecting the charger from the battery pack allows the individual cells to 'level out'. Plug the charger back in again. allow to charge, unplug, leave a few seconds, plug in again. Do this a few times. Should give you a better charge.
I do not know the electronics within the minelab charger, and if there is any regulatory/monitoring circuitry inside or not. but I beleive the theory will work with them.
To see this effect 'in action' try charging any other camera/video battery you have that has a charger that has charging/charge complete lights on them. Once the 'charge complete' light comes on for the first time, remove battery, and re-insert, again wait for 'charge complete'. As you keep repeating this cycle, you will notice that the time until the 'charge complete' light comes on keeps reducing. When it comes on within a few seconds of re-inserting the battery, you can be fairly sure the battery has a full charge.
Neil
I'm using the minelab 9.6V , 1500mAH and after using it for two years now have finally ran it till she went dead.(I've been charging it up but never ran it completley out of juice)