i picked up a black and decker battery charger up at a garage sale  and it has 3 settings for amps 2 amp ,4amp ,6 amp . i have to buy a new battery and was wondering if any particular setting better for charging a deep cycle battery and keeping it healthy. thanks    

you need to find out what the max amp charge the battery can handle. my cabelas 24 series agm can handle 14 amps. i would think that you could charge at 6 amps if it is an autocharger that will drop amps as the battery gets full.

Pretty sure its always better to charge on the lowest setting which is also the slowest. So unless you are pressed for time I would use the 2 amp setting.

You can use any of those settings but with the 2 am and heavy use it may take more than a full day to recharge the battery.  If you don't own a hydrometer, get one with volt showings not ball floatings.  Charge the battery to 12.7 volts.

If it is an older style charger, and your description suggests it is,  you need to measure the voltage after it has fully charged the batteries.  If this voltage is above about 13.6 volts, it is not a "smart" charger and you will have to turn it off when charging is finished so you don't cause your batteries to lose liquid.

The recommended charge rate depends on the size deep cycle battery. The approximate charge rates for the typical group 24 will charge at eight amps, a group 27 will charge at 10 amps and a group 30/31 will charge at 12 amps.   The only time you would use two amps is when charging your little lawn/garden  battery.

I would never leave you're standard Automatic charger connected to a battery once it has reached full charge and cut off, don't care whose brand it is. Doing this is only going to fry your battery in most cases.

Your best chargers will have a micro-processor controlled system that charges in three phases, fast, absortion and float with a float voltage of 13.2 - 13.6 volts. They will also be selectable for battery type. Most of these chargers you can leave connected 24/7. Some of the cheaper ones are not real accurate on their float voltage so I would check it after 24 hours the first time and make sure it's not above the battery manufactors recommended maintenance voltage, which does vary by manufactor and type battery.