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Re: charging question

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  • mike_dot_groves
    Sorry, but you missed my point completely. I was not talking about C , nor did I ever refer to it. I simply stated the BC346XT has a pretty much constant
    Message 1 of 14 , Oct 29, 2011
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      Sorry, but you missed my point completely. I was not talking about "C", nor did I ever refer to it. I simply stated the BC346XT has a pretty much constant current charge rate of 200mA. If you want to calculate "C" for any given cell size, be my guest.

      My point was directly answering the OP's question. Namely, "How do you know when your scanner is charged when using the adapter?"

      Since we are dealing with a constant charge rate of 200mA, the ONLY variable we as users get to play with is TIME. So the correct question should be, "How long should I set my radio's charge time for?"

      The answer depends on the capacity of the batteries installed and how much residual charge they have when the charge cycle starts. For the latter part, I will assume they are near empty. A bit of overcharging when trickle charging is not the worst thing for a battery.

      [Batteries 101:] When charging batteries, more energy must be supplied to the battery than its actual capacity, to account for energy loss during charging. How much more? (Glad you asked.) When trickle charging, the RULE OF THUMB is about 1.4 to 1.5 times their capacity.

      So for a 2000mAh battery, the goal would be to feed it with 2000mAh x 1.5, or around 3000mAh total of electricity. Since we know the BC346XT has a fixed charge rate of 200mA, then simple math tells us it will take around 14-15 hours to achieve that goal. (200mA x 15h = 3000mAh)

      From that, we can derive the following charge time chart for different battery capacities...

      800mAh = 6 hours
      1200mAh = 9 hours
      1600mAh = 12 hours
      2000mAh = 15 hours
      2400mAh = 18 hours
      2800mAh = 21 hours
      3200mAh = 24 hours

      These are WORST CASE charge times based on a 200mA charge rate and a completely drained set of batteries. There are many factors that may reduce the above times significantly. For example, since the scanner gives you a low battery warning long before they are actually "dead", they may still have a pretty good charge left on them. The same is true if you use some of the higher capacity batteries; you might only drain them half way by the time you get ready to charge them again. This is particularly true if you use a car adapter while driving around, then want to also charge them overnight. Also, the batteries you own may not actually have the full capacity stated on their jacket, especially if they have been used a lot. You get the idea. All these factors can reduce the total charge time needed.

      As you can see, there's no easy one-size-fits-all answer to your question. It all depends on your usage, batteries, etc.

      One easy way to tell if the batteries are full, is to turn on the scanner, press the volume knob down and read the voltage in the top-right corner of the display. If it's still plugged in and charging, anything over about 4.3V means they are done. Right after disconnecting from the charger, a full set of NiMH batteries will be around 4.2 to 4.3V.

      Hope this helps.

      --- In BC346XT@yahoogroups.com, MCH <mch@...> wrote:
      >
      > Actually, the rule of thumb for trickle charging IS 0.1C, or 10% which
      > makes the charge current just about dead on. (not surprising)
      >
      > For fast charging, you can go up to about 1C (or 100%), but the best
      > charge rate is usually specified at about 0.5C (50%) and I typically use
      > 0.25C (25%). And fast charging definitely demands charging the cells
      > individually.
      >
      > I've never heard of 1.5C being recommended, let alone the rule of thumb.
      > I'm sure there are chargers that may go that high, but the better ones
      > will not.
      >
      > Even my Maha charger will only go to 2A which would be 1C for 2000 mAH
      > cells.
      >
      > Joe M.
      >
      > mike_dot_groves wrote:
      > >
      > > The BC346XT charges at 200mA, plus or minus about 10%, depending on whether the batteries are empty or full. (Measured with my Fluke DMM.)
      > >
      > > The rule of thumb for charging is to feed them with about 1.5x their capacity. This means if you want to fully charge 2000mAH batteries that are empty, you need to give them about 3000mAH of juice. At the 200mA rate, that means charging them for 3000/200 or around 15 hours.
      > >
      > > --- In BC346XT@yahoogroups.com, "Mark W. Walton" <mark.walton@> wrote:
      > >> I based my estimate on the charging time of an auxiliary charger I have. I don't know what the BC346XT's charging rate is.
      > >>
      > >> Mark Walton
      > >> mark.walton@
      > >>
      > >>
      > >> -----Original Message-----
      > >> From: BC346XT@yahoogroups.com [mailto:BC346XT@yahoogroups.com] On Behalf Of Paul Opitz
      > >> Sent: Sunday, October 23, 2011 10:29 PM
      > >> To: BC346XT@yahoogroups.com
      > >> Subject: Re: [BC346XT] charging question
      > >>
      > >> Further to the Moderator's note, 2 hours is not going to come even close to
      > >> fully charging fully discharged batteries of any capacity. 2300 mAH batteries
      > >> are going to take 14-16 hours.
      > >>
      > >>
      > >>> From: Mark W. Walton <mark.walton@>
      > >>> To: BC346XT@yahoogroups.com
      > >>> Sent: Sun, October 23, 2011 9:13:08 PM
      > >>> Subject: RE: [BC346XT] charging question
      > >>>
      > >>>
      > >>> MODERATOR'S NOTE:That only indicates that the charge timer has elapsed, not that
      > >>> the batteries are fully charged.
      > >>>
      > >>> When it's charging, "Normal Charging" appears on the display. When the display
      > >>> blanks out, then the batteries should be fully charged. For my scanner, I have
      > >>> the charge time set to 2 hours, that's ample for the supplied batteries (1800
      > >>> mAh) and for some spares (2600 mAh).
      > >>>
      > >>> Mark Walton
      > >>> mark.walton@
      > >>>
      > >>> -----Original Message-----
      > >>> From: BC346XT@yahoogroups.com [mailto:BC346XT@yahoogroups.com] On Behalf Of Paul
      > >>> Opitz
      > >>> Sent: Sunday, October 23, 2011 10:05 PM
      > >>> To: BC346XT@yahoogroups.com
      > >>> Subject: Re: [BC346XT] charging question
      > >>>
      > >>> There is no way to positively detect a full charge in the scanner other than
      > >>> charging for the maximum duration.
      > >>>
      > >>>> From: Karen <kpagnotti@>
      > >>>> To: BC346XT@yahoogroups.com
      > >>>> Sent: Sun, October 23, 2011 8:48:58 PM
      > >>>> Subject: [BC346XT] charging question
      > >>>>
      > >>>>
      > >>>> How do you know when your scanner is charged when using the adapter?
      > >
      > >
      > >
      > >
      > > ------------------------------------
      > >
      > > Yahoo! Groups Links
      > >
      > >
      > >
      > >
      >
    • MCH
      Yes, I see what you were saying now. You were talking about the total charge a cell will require, and not the charge rate. When you said The rule of thumb for
      Message 2 of 14 , Oct 30, 2011
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        Yes, I see what you were saying now. You were talking about the total
        charge a cell will require, and not the charge rate. When you said "The
        rule of thumb for charging is to feed them with about 1.5x their
        capacity.", I thought you were talking about the charge rate, and 1.5
        times their capacity would be way too high.

        Of course, the total charge will depend on several factors - including
        the condition of the cell. Newer cells will generally require much less
        than 1.5 times their capacity while older ones may require more. You can
        tell the cell condition by the release of heat during the charge
        process. The more heat released, the less efficient the transfer and the
        more total charge will be required to reach full capacity (which will
        change as the cell ages).

        Joe M.

        mike_dot_groves wrote:
        >
        > Sorry, but you missed my point completely. I was not talking about "C", nor did I ever refer to it.
      • Paul Opitz
        With the added caveat that unlike NiCD, which are endothermic during normal charge (chemical process absorbs heat), NiMH are exothermic during normal charge.
        Message 3 of 14 , Oct 30, 2011
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          With the added caveat that unlike NiCD, which are endothermic during normal
          charge (chemical process absorbs heat), NiMH are exothermic during normal
          charge. That is, it is perfectly normal and expected for NiMH cells to
          continuously generate heat during the charge cycle even when charging
          efficiently and not yet in overcharge.

          (A lot of people get concerned that the batteries are immediately getting warm
          shortly after charging starts.)


          >
          >From: MCH <mch@...>
          >To: BC346XT@yahoogroups.com
          >Sent: Sun, October 30, 2011 9:34:44 AM
          >Subject: Re: [BC346XT] Re: charging question
          >

          >Yes, I see what you were saying now. You were talking about the total
          >charge a cell will require, and not the charge rate. When you said "The
          >rule of thumb for charging is to feed them with about 1.5x their
          >capacity.", I thought you were talking about the charge rate, and 1.5
          >times their capacity would be way too high.
          >
          >Of course, the total charge will depend on several factors - including
          >the condition of the cell. Newer cells will generally require much less
          >than 1.5 times their capacity while older ones may require more. You can
          >tell the cell condition by the release of heat during the charge
          >process. The more heat released, the less efficient the transfer and the
          >more total charge will be required to reach full capacity (which will
          >change as the cell ages).
          >
          >Joe M.
          >
          >mike_dot_groves wrote:
          >>
          >> Sorry, but you missed my point completely. I was not talking about "C", nor did
          >>I ever refer to it.
          >
          >
          >

          [Non-text portions of this message have been removed]
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