JBE..Not all batteries are created equally nor from the same compounds. Some have large fuel tanks (mah) and some have small fuel tanks. The higher the number, like 2600mah, the longer they will provide power to equipment, all other things being the same. NiCads are OLD technology. They were great a decade ago when all we had were carbon or lead acid to put in our equipment. However, they had a memory. If you didn't use all the power out of the battery it tended to remember how much was left when you refilled the tank lat time and after awhile the battery assumed since you only put a little fuel into it, it must really have a smaller tank than originally installed. NiMH are newer techonology and have no memory. That means use it.Recharge it without waiting for it to be totally discharged, and the capacity remains very much the same. A down side of NiCads and Nimhs are they don't retain their charge when sitting on the shelf or in your detector bag. However, in the last year or so, you can now shop for and purchase NiMHs that many manufacturers claim will hold their charge up to 80% capacity for one year. I suspect that is almost as good as Alkalines.
Batteries are probably more important than the coil you use but they get little respect or attention from us, generally. Most detectorists have certainly read reviews about the next coil they'll choose but my guess is darn few surf the internet to read reviews about batteries. With some looking one can buy rechargeables with a charger, for about the same price you pay for a box of Alkalines like at COSTCO or Wally's world. From my experience I would buy the best charger you can afford (within reason). Mine cost $70 and it will, with one option, evaluate a battery, and then totally discharge it (controlled electronically so as not to damage the battery), and the recharge the battery. I have gained batteries for my use that others have discarded because previous owners thought they were defective. My charger has a slow or a rapid charge feature. Usually slow is easier on the battery.
Consider traveling to a Radio Control car or airplane/helicopter or a HAM forum and go the section of the forum that talks about batteries. Read for and hour or so and you'll gain a real understanding of what battery to use in what application and how to charge it and store it. The nasty cells are Lithium Polymer. They pack a heck of a punch and run the electric motors in the cars and planes. It's recommended that you charge those batteries inside a fireproof enclosure as there are reports of improper charging causing the battery to explode and some hobbyists have lost family stuctures because of that.
http://www.all-battery.com/volumebatchchargerwithaaaaarecharageablebatterypackage.aspx There is a site that give you many expample of chargers and batteries. Be sure to do your homework and Murphy will stay away from your detecting batteries....Jim
