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Charging X2 batterys

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  • Charging X2 batterys

    Does it hurt the X2 batteries to leave them on the charger for an extended length of time? I now have a B&D 14.4 volt comercial (Dewalt) and a very old Craftsman 7.2 volt drill, the batteries are on the charger 24-7. Both work fine.

  • #2
    Yes its perfectly fine to do so. The fans will still run, and the charger will drop to a trickle charge if the pack goes down in voltage.


    • #3

      First, the "rapid" charger does not end its cycle with a "trickle" charge, which implies a small but continuous flow of current into the battery. A "trickle" charge will necessarily raise voltage to the point where it will fry the battery.

      Second, while some batteries (notably flooded cell batteries) can sustain extended exposure to a "float" charge cycle (which is how the "rapid" chargers end their charge program) without damage, NiCad cells cannot. Their electrolyte, nominally in paste form, will dry out and crystalize.

      Third, the fans in a charger are there to dissipate heat from the charger's electrical and electronic components; they do nothing about dissipating heat from the battery.

      An accepted rule of thumb is this: when the lights on a "rapid" charger for NiCad battery packs go from "charging" to "finished," the battery has recovered approximately 80% of its nominal capacity. It should be left on the charger for an additional period of not less than an hour or two, and not more than 3-6 hours.

      [ 10-29-2003, 11:36 PM: Message edited by: RGad ]


      • #4
        On close inspection of my new toy, I find that when the battery is placed on the charger it opens a small door on the charger and the fan blows air through the battery pack and out holes in the bottom of the battery pack. This cools the batterys while charging.

        The concern I have is if the drill is not used for a peroid of a few weeks will the battery hold a charge or will I have to recharge them before using the drill.

        Another option would be to put a timer on the charger to allow for a short charge time (1 or 2 hours) each day. Would this be harmfull to the battery pack?


        • #5
          1. NiCads do shelf discharge. But don't worry about it.

          2. Pre-charging is bad for the NiCads because they should not be charged until they have become discharged (where for present purposes discharged means a cell voltage of about 1.0 - 1.05V -- not completely shorted by leaving a light bulb on it overnight). Periodic charging is a form of pre-charging. Both will prematurely consume your battery's life.

          3. For public safety applications, where we have a bunch of batteries sitting around shelf discharging, but we may need them some day and if we do we'll need them right away, we use a battery conditioner. Basically, the conditioner leaves the battery alone for a programmed amount of time (5-10 days), after which (i) it discharges the battery on a carefully controlled load to a carefully controlled steady state voltage, and (ii) it then recharges the battery under equally carefully controlled conditions. Battery conditioners cost a lot of money.

          4. For carpenters' power tools, all you have to do is have a couple of batteries. Leave the batteries alone when the tool is not in use, and then when you take it off the shelf, use the battery that is on it until the motor begins to slow. Then change batteries and put the depleted one on the charger.