Your particular application will decide whether you need a fast charger which can charge the batteries in a couple of hours, or a slower charger which might take 5 or 6 hours to charge the batteries.

Fast – Fast chargers will charge 4 x 2100mAh batteries in 2-3 hours. Fast chargers are useful if you are likely to use a lot of battery power in a short time.

Quick – Quick chargers will charge 4 x 2100mAh batteries in 3-4 hours. Quick chargers are useful where batteries can be left for several hours to charge.

Standard – Standard chargers can take up to 8-9 hours to charge 4 x 2100mAh batteries. These chargers are best left to charge overnight.