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  1. #1
    Plutonium Lounger
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    I just bought a couple of replacement batteries for my Palm Treo 680 and I've got a question. I've had this phone for two years and have always kept one battery on a standalone charger while the other is in the phone. Whenever the remaining charge indicator on the phone gets down close to 10% I usually switch batteries. The instruction sheet that came with the batteries said that Li-ION batteries do NOT require "deep cycling" and prefer a shallow discharge.

    Not being sure what exactly a shallow discharge is, I went looking and came up with Discharge Methods where they say a LOT of stuff that's way over my head, but this is more down to earth:

    Manufacturers rate the lithium-ion battery at an 80% depth of discharge.
    Repeated full (100%) discharges would lower the specified cycle count.
    It is therefore recommended to charge lithium-ion more often rather than letting it discharge down too low.
    Periodic full discharges are not needed because lithium-ion is not affected by memory.

    By simple math, is that telling me that I should change my using strategy and start swapping the batteries at 20% remaining, or thereabouts?

  2. #2
    New Lounger
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    Lithium Ion batteries are quite complex, as you have found.

    It turns out they have something beyond your control also (so why am I saying? A: In the interest of just being .... interesting.

    If you FULLY charge an Li battery, it will last the longest RUN TIME, but the shortest overall LIFETIME.

    If instead you don't fully charge it, and as you have found, don't fully discharge it, then you get shorter run times, but longer overall (let's call it "calendar") battery life.

    The worst thing you can do is either extreme: Always on a charger (at least I've seen them go bad that way) or leave them "alone" SO long or starting in a discharged state.

    Apparently Li batteries will die completely - with an associated "puffyness" i.e. the battery isn't solid any more, but as if it were blown up a bit with gas pressure. (maybe it is).

    SO it would seem from your comments and mine to maybe swap batteries much more often, in order to be able to continue to use the same batteries for the longest time.


    P.S. when I switch to a new cell phone, I keep the batteries charged, and use them - I find that most cell ph batteries can be accessed via alligator clips, and the 3.7 or so V they supply, run the little 2-5.5V PIC "Blinkies" such as (great fun!) from 2DKits.com. If you want I can tell you where to clip the "other end" of the 'gator clips to the board, or you can psych it out yourself since full schematics etc are given for these mostly <$20 kits containing multiple LEDs, resistors, switches, IR detector & transmitter, and a MicroChip PIC "computer".

  3. #3
    4 Star Lounger pauliez's Avatar
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    Quote Originally Posted by Ward Christensen View Post
    Lithium Ion batteries are quite complex, as you have found.

    It turns out they have something beyond your control also (so why am I saying? A: In the interest of just being .... interesting.

    If you FULLY charge an Li battery, it will last the longest RUN TIME, but the shortest overall LIFETIME.

    If instead you don't fully charge it, and as you have found, don't fully discharge it, then you get shorter run times, but longer overall (let's call it "calendar") battery life.

    The worst thing you can do is either extreme: Always on a charger (at least I've seen them go bad that way) or leave them "alone" SO long or starting in a discharged state.

    Apparently Li batteries will die completely - with an associated "puffyness" i.e. the battery isn't solid any more, but as if it were blown up a bit with gas pressure. (maybe it is).

    SO it would seem from your comments and mine to maybe swap batteries much more often, in order to be able to continue to use the same batteries for the longest time.


    P.S. when I switch to a new cell phone, I keep the batteries charged, and use them - I find that most cell ph batteries can be accessed via alligator clips, and the 3.7 or so V they supply, run the little 2-5.5V PIC "Blinkies" such as (great fun!) from 2DKits.com. If you want I can tell you where to clip the "other end" of the 'gator clips to the board, or you can psych it out yourself since full schematics etc are given for these mostly <$20 kits containing multiple LEDs, resistors, switches, IR detector & transmitter, and a MicroChip PIC "computer".
    You are so right.

    I found that out with my power tools.

    Never fully charge the batteries, but switch them when they are just past half charged.

    The second sets I bought for my tools have so far lasted twice as long as the previous set.

    I have been doing the same with my cell and anything else that requires a rechargeable battery.
    Catz

  4. #4
    Super Moderator WebGenii's Avatar
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    I remember reading recently that the biggest killer of battery life is overheating. A cell phone left on the dash of a car for example.

    I wonder if we'll get longer battery life in this weather?
    [b]Catharine Richardson (WebGenii)
    WebGenii Home Page
    Moderator: Spreadsheets, Other MS Apps, Presentation Apps, Visual Basic for Apps, Windows Mobile

  5. #5
    Plutonium Lounger
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    Thanks for the comments so far folks! As I said, this Palm is now two years old and the original two batteries I bought with it are still serviceable but lasting somewhat shorter time than they used to. I was advised a long time ago (when I had my previous phone) that cell batteries "usually" last two or three years, hence my decision to buy two replacements now.

    I use a standalone charger only because my phone needs to be operational 24/7. (*) Since I use a standalone charger I have no way to measure the time it takes for "full charge" and simply put a discharged battery in until I need it. On the other hand, I CAN and do use the battery meter in the phone to watch for the degree of discharge. I think for these two new ones, I'll change my strategy and recharge at "about" 20% remaining rather than my aforementioned 10% or so.

    Batteries aren't cheap, but if I get two or three use from them, I guess I can't complain. Thanks again everyone!



    (*) With my wife in a nursing home, I keep my phone under my pillow at night (don't laugh) just in case of a medical emergency.

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