Detacc also had a step up voltage regulator I.e turns your 6v battery into 7.2v. I think this is ok on the SD series (definitely ok on SD2200D) but GP series is 6.7v max I think?
From
http://www.nuggethunting.com/whats_new2.htm:
"Got too many 6 volt batteries and, chargers and assorted goodies but you would still like to have 7.2 volts plus power for your SD, without having to buy different batteries, chargers etc. The new DeTacc Super Regulator made especially to my specifications. It takes your standard 6 volt Minelab battery and boosts it to 7.2 plus volts. And it maintains that constant 7.2 volt output until your battery voltage drops to 5.6 volts.
If your battery gets too low, the low battery warning light on the regulator will come on to advise you to change batteries!
The regulator is small and attaches to the side of your detector with the supplied velcro. You plug the regulator into the detector and the power cord into the regulator.
In this case I have actually ran the output of the voltage regulator through our new VOLTAGE/AMPERAGE meter to show you that the 6 volt battery is being boosted to 7.25 volts !
And here is the best part, the step up regulator is 90% effective in power consumption. Usually you will get 1 hour of use for each amp hour of power the battery has. So if you are using the 6 volt 12 amp hour battery you will have more than enough power for a whole day of detecting with one battery!"