The Whites XLT instructions say go for 22 hours for the initial charge (ie completely uncharged batteries), but it doesn’t say how long for subsequent charges. So how long do you do it?
After your initial charge, there is no need to fully discharge your battery as it wont develop a memory. I have had mine 3 and a half years, and although my battery does not last as long as it used to, I still get 4 – 6 hours out of it depending on the settings used.
This is so long as whites have not changed the batteries that are supplied along with the detector
As for re-charging the battery. This will depend on how flat it is. If mine is quite low I put it on charge the night before I am going detecting (10pm) and leave it till the morning. But sometimes I might only need to top it up for an hour or two.