Cheers, I bought my charger from petrol station, that way I charge it up on the way to site, after a days play, probably only takes 30 mins to top up again! I believe there either nimh or lithium ion, both of which have no 'memory' so don't need discharging completely and then recharging.
Although I would occasionally do it to condition the battery! Difficult to do though as when the battery gets low, marker can become unreliable.