You can use the rechargeables in your Ace 200 if they're the 1.2 volt ones. I had an Ace 250 some years ago and they worked just fine.I was wondering if I should buy some rechargeable AA batteries for my Garret Ace 200. I probably will anyway, but since rechargeable batteries have a lower voltage than alkaline batteries, I was wondering if it would be bad for my detector. Thanks!