Onlybatterypacks.com And they have a Minelab Page with Batterys and chargers and they do not get damaged fast charging,Since i purchased from them my Batterys have Lasted longer and hold up much better then the after market Kellyco would sale with OnlyBatterypacks you purchase the battery and it plugs in like a nine volt would,Instead of waisting money buying the whole battery casing again, and spending 100 dollars 4 a battery plus shipping.
Update fast charging the original Batterys is not good,But at this website they sale a better battery and it replaces the inside shell of the Minelab Battery and plugs in and u charge it with the regular screw on connector,and on there minelab page they sale the quick charger and once its charged the light Yes they have a charger with a light so you know when your battery is fully charged.
And once its charged it continues to slow trickle charge the battery, Look at what they have to offer before someone convinces a person thats not a good thing to do, I researched this two days before i ordered from them and have been happy ever since. Good Luck Everyone.
It amazing i have posted this site on other topics, As far as the O ring i used diver grease to keep the water out on the o ring and screwed on the charger cap and stood up in the sink full of water to test leakage,You sure dont want to test in the ocean.