R n B innovations make a great rechargeable battery for the Garrett AT series detectors. Last 30 - 40 hrs s charge. I put 12 hours on my At Max and it's down one bar from full chatge.
I'm skeptical of the RnB rechargeable on my AT Max. I haven't timed it from full charge yet, but the lifespan seems about the same or shorter overall than standard alkalines. Within the first hour hunting, the Max drops from 4 bars down to 3 while using the RnB. I recently decided to keep using the RnB across several hunts to see how long it might last between charges. After dropping to 3 bars quickly, it lived there for quite a while - I'd say I hunted 3 or 4 times for a couple hours apiece and it sat at 3 bars. That seemed great - however, on the fourth hunt, it finally dropped to 2 bars...maybe an hour after it dropped to 2 bars, I picked the machine back up after digging a plug, and it was dead. It still showed 2 bars when I put it down - I was monitoring it quite closely because I intended to change out as soon as it hit 1 bar, as the Garrett manual suggests.
Anyway, my point is, I was quite concerned to see the RnB drop from 2 bars to dead with no real warning. In hindsight, the detector was behaving rather erratically while at 2 bars - the tones seemed clipped and the detector became noticeably chattier which I initially attributed to ground conditions. Instead, it appears the RnB unit needs to be recharged immediately on reaching 2 bars, as opposed to 1 bar for alkalines as suggested by the Garrett manual. Overall, I estimate that I got 10-12 hours of hunt time on one charge of the RnB. It's better than constantly buying alkalines, but far less time than I was led to believe when making the rather pricey purchase. Perhaps mine is defective? I guess I need to start timing from full charge to put firm numbers together. And it's important to note, for all of my hunts, I'm constantly using the wireless headphones.
My backups are a set of Panasonic Eneloop Pro rechargeables. Their lifespan is noticeably shorter than alkalines, but I was able to hunt with them down to one bar with no noticeable adverse affects.
Depending on your machine those Rechargable s may or may not work. Most rechargables are only 1.2 volts versus 1.5 volts for alkaline. If your machine uses 8 AA batteries you are only getting 9.6 volts versus the 12 volts would get from 8 alkaline batteries. You machine may not get enough voltage to operate properly for any length of time
Interesting point - the Garrett manuals for both my Ace 400 and AT Max specifically state that rechargeable NiMH batteries can be used, the only caveat being reduced life per charge. They don't specifically mention the voltage for the batteries, but I'm assuming that Garrett knows that 1.2V is the standard for rechargeables? My knowledge of electricity goes little beyond just calling it sorcery & magic, but I always thought the battery's amp-hour rating was what dictated battery lifespan in a given device, assuming the voltage was correct. I didn't think about it before, but how much voltage reduction can a detector withstand before performance drops? Both the AT and Ace series use 4 AAs, so there's a 20% difference drop using rechargeables (4.8v versus 6v). Sounds pretty significant...anyone with better electrical knowledge know better??
Now that I'm all in with rechargeables in the detector, I guess I better call Garrett and get the info right from the horse's mouth...
