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Prolonging battery life

Discussion in 'GENERAL Wireless Discussion' started by viewfly, Oct 23, 2006.

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  1. viewfly

    viewfly Mobile RF Advisor
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    Hi everyone,

    I think something like was probably posted before, but a refresher on it came up in the 6131 Thread on WA.

    I was doing a little research on charging li-ion batteries, the kind in our phone.

    It supports that charging frequently, without going to a dead battery, is the best way to preserve your battery. Going to full discharge, although somewhat protected by the phone electronics, is not what Li-ion batteries like.

    Some of us have gotten into the habit of charging our phones in the morning, each day, during breakfast or whatever, so we have a full charge during the day. It takes only 2 hours max on the 6131, and most times it is only 1/2-1 hour to top it off. Most people charge at night, or worse, charge it the whole night, which is not a good idea: overcharging will kill a battery.

    "A lithium-ion battery provides 300-500 (full) discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges."

    Also, the battery's lifetime decay starts the day of manufacture, so buying a 'fresh' battery, but an old one (or keeping it around as a unused spare) is not a great idea. So maybe those cheap OEM-like batteries I sometimes see, are outdated or old. Buyer beware!

    But one thing I didn't know, regards the battery's charge Icon on the phone. I don't know if it is true for Nokia's but apparently it gets recalibrated only with a full discharge. So the recommendation is to full discharge every 30 cycles (in our case once a month).

    "Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate. "

    It doesn't mean that the battery has less charge, only that the phone's battery meter thinks so...and this may turn the phone off early. I don't know for certain.

    So the practice we have is a good one, but every month , let it go down to shut off. Whatever works, or at least beware this may be going on.

    Reference: http://www.batteryuniversity.com/parttwo-34.htm

    Wikipedia has also some info and it agrees with what my professional battery co-workers have told me : http://en.wikipedia.org/wiki/Li-ion_...n_battery_life

    "A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. This drawback is not widely publicized"

    and

    " Unlike NiCad batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a longer time, they should be brought to a charge level of around 40%. Lithium-ion batteries should never be "deep-cycled" like NiCd batteries"

    The exception being, the first time you get the Li-ion battery: do 3 full charge/discharges first, to maximize battery life for future partial charges.

    The daily morning charge is working out well for all of us. I like having a full battery during at start of the day, esp after 9/11...never know when you wish the battery was not half empty. But be careful not to overcharge, unless you know for certain that the charger has turn off protection. The Nokia 6131 manual specifically states not to leave the charger on longer than necessary.

    vf
     
    #1 viewfly, Oct 23, 2006
    Last edited: Oct 23, 2006
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  2. charlyee

    charlyee Ultimate Insanity
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    viewfly, thanks for the great information. How about asking one of the moderators to make this into a "sticky" so this one does not get buried like the one posted by Tony E did.:)
     
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  3. Jay2TheRescue

    Jay2TheRescue Resident Spamslayer
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    I vote for sticky status too. I've noticed that the past few years the phones I've gotten since my v60 have been much better than my V60 and StarTac were. My StarTac had to have its battery replaced at 18 months, and my V60's battery was limping on its last legs when I bought my V551. My V551 is about 3 years old now and I still have no problems with it after charging nightly.

    -Jay
     
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  4. Tony E!

    Tony E! Retired Mod
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    Good memory Charlyee....;)

    I'll just make this one a sticky since it has the same info and link as the one i posted.
     
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  5. viewfly

    viewfly Mobile RF Advisor
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    Thanks Tony. Making this a sticky could be useful.

    vf
     
  6. Fire14

    Fire14 Easy,Cheap & Sleazy
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    I also agree this should be a sticky, there is some good information here & I learned something new today from it.
    I usually let my batterys go down before charging them, even though I know they don't have the memory effect of Ni-Cads, I thought I was doing something good for the battery.

    As for buying spares, I didn't know about the shelf life either & recently bought a spare for my wifes & my Moto's.
    Thanks for the post viewfly.
     
  7. ian1001

    ian1001 Junior Member
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    do these same rules apply to li-polymr(sp?) batteries?
     
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  8. bobolito

    bobolito Diamond Senior Member
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    What I question is that in this day and age, are you sure that all phones don't have an overcharge protection as a standard feature? I mean, if the phone is intelligent enough to tell you "Charge Complete" (I haven't seen the first phone that doesn't) how do you know it is still charging the battery? I would think that as soon as the phone says "Charge Complete", the phone will stop the charging flow to the battery, or at least reduce it to a minimum just for the sake of maintaining the battery full. After all, even if powered off, the phone has some control using software over the energy that gets to the battery.

    About charging in the morning, I wish I could, but I find it difficult to be able to do that. I have to get to work and my phone takes about 2 hours to charge. I guess I could put it in the USB charger in the computer at work, but I would have to unplug it every time I have to step out of the office and I think that defeats the purpose. The nature of my job requires me to be in and out of the office constantly. After I get home I constantly use my phone. So the only time the phone has a chance to get uninterrupted charge is at night after I go to sleep. At night, my phone still has some 25% of the charge left over.
     
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  9. viewfly

    viewfly Mobile RF Advisor
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    A very good question. No, I'm not sure. My Dell computer states that internal electronics prevent overcharging - and not to worry.

    My Nokia car charger says the same. P.S. I know that not all car chargers have this function - esp the cheap ones. I took the Nokia apart once, and there is a small pc board inside, and a sense line that is made use of.

    My Nokia 6230 manual didn't give any warnings, but the 6131 manual states cleary not to overcharge the phone - implying that the wall charger provided and the phone do not protect for overcharge. On the other hand, Nokia manuals have been incorrect and contradictory in the past (take the example on the 6126 vs 6131 - each manual states a different warning on where not to place the fingers while talking).

    So it's is an open question for me - but for now, I will play it safe, and not charge my phone all night long.

    P.S. saying 'charge complete' is just stating that the voltage was achieved - it doesn't imply that the phone/charger will prevent overcharging. Certainly my old Nokia wall chargers are just dumb ac/dc transformers.
     
  10. viewfly

    viewfly Mobile RF Advisor
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    I don't know for certain about li-polymer - but my guess, from reading the wikipedia information on this li variant, is that the same rules apply. wikipedia does say that li-polymer has a faster aging rate than li-ion (not a good thing), but battery tech changes rapidly. I didn't find anything as specific about li-poly as what is written for li-ion.
     
  11. charlyee

    charlyee Ultimate Insanity
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    My 6131 wall charger specifically says "low standby power consumption ". This would lead me to believe that after the phone is charged,the charger goes into a standby mode and some amount of trickle charge is still present.
     
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  12. viewfly

    viewfly Mobile RF Advisor
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    My UK Nokia charger that came with my phone, says nothing like that. Only that is it puts out 5V @350mA. It is made in China.

    Maybe your is better than mine. what is the DC output?

    P.S. my charger AC-3X has the letters LPS on it. The web page says it is Low standby power, as yours does. I really don't know what that means. I note that none of the other Nokia chargers say that , even the car charger.
     
  13. Jay2TheRescue

    Jay2TheRescue Resident Spamslayer
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    I know my car chargers all said that they switch to trickle mode when the battery is full. I still use the charger I bought for my V60t 5 years ago on my V551 and my HS820 headsets and have not experienced any bad batteries. (Except on the V60 - that battery was toast when I upgraded.)

    -Jay
     
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  14. viewfly

    viewfly Mobile RF Advisor
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    I found this 2006 article in Electronic Design (http://www.elecdesign.com/Articles/Index.cfm?ArticleID=12195&pg=1).

    If the Nokia phone/charger has any intelligence, it should terminate the charge, not continue a trickle charge:

    "The continuation of trickle charging isn't recommended for Li-ion batteries. Instead, charge termination is a good option. For NiMH batteries, a timed trickle charge ensures 100% of battery capacity use"

    According to the article, the preferred Li-ion charging cycle is:

    1) if battery voltage is depleted below 3v, trickle charge until reaches 3V
    2) at 3v constant current charge until battery voltage reaches 4.2 V
    3) at 4.2 volts, constant voltage charge for a specific time and/or until charging current drawn by the battery reaches some minimum value (normally a couple of hours)
    4) Terminate charge - do not trickle.

    Now, from what I've read, the phone's probably never lets the battery get to below 3V, so probably there is only stages 2 and 3 happening above.

    So, Bobolito, the real question is how smart are the chargers? Do they follow the above? I don't know, but even from Nokia the information is contradictory. One Nokia web page says they use a 'Power Management System' to prevent overcharging (http://www.nokia.ca/english/products/accessories/why_nokia.asp).

    And I will stand corrected (had a senior moment), the 6230 & 6131 manual say the same thing:

    "Unplug the charger from the electrical plug and the device when not in use. Do not leave fully charged battery connected to a charger, since overcharging may shorten its lifetime."

    Both of these Nokia statements could just be marketing/legal hype.

    Probably the best thing is to have one of my EE friends actually measure the current/voltage used by my Nokia charger during the charging cycle.

    Stay tuned. My curiosity is peaked. - But you have to do what is necessary - I've used my phone heavily on travel, and it's all I can do to fall into the hotel bed, and let the phone charge all night. I think the main point, for non-power users, is to charge daily instead of intentionlly running for days to bring it down to shut off - there no real value in doing that.
     
  15. Fire14

    Fire14 Easy,Cheap & Sleazy
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    Per the Motorola User Manual for the V600 (the closest to my V635) it say's you can leave the charger hooked up after the charge is complete with no problems or damage to the battery. (under Charging the battery)

    http://www.motorola.com/mdirect/manuals/v600_manual_ENG.pdf

    I didn't check any other models yet.

    Which is good to know, since the only time I really have to charge my battery is over night while sleeping as well.
     
  16. charlyee

    charlyee Ultimate Insanity
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    Lol viewfly, no we have the same charger as far as specifications go, the only difference is mine is the AC-3U, which is the US charger and is for all the Nokias that have the mini probe like all the 610X serires, 6126, 6133, 6133.....
    Now you did it, I tried to find a clamp on mA meter but working in an environmemt that considers 600 volts low voltage, and 4160 volt, medium voltage that quest proved to be completely futile.
    Yes I completely agree and I for one, was certainly guilty of that.

    You have my curiosity peaked also, so I did some research by dusting off my text books and some web browsing, here are bits and pieces of information I gathered.

    1. Lithium ion polymer batteries, or more commonly lithium polymer batteries (Abbreviated Li-Poly or LiPo) are rechargeable batteries which have technologically evolved from lithium ion batteries. Ultimately, the lithium salt electrolyte is not held in an organic solvent like in the proven lithium ion design, but in a solid polymer composite such as polyacrylonitrile. There are many advantages of this design over the classic lithium ion design, including the fact that the solid polymer electrolyte is not flammable (unlike the organic solvent that the Li-Ion cell uses); thus, these batteries are less hazardous if mistreated.

    2. The chemistry is basically the same for the the Lithium Ion & Lithium Polymer batteries, so charging methods should be the same.

    3. The lithium ion battery is easy to charge. Charging safely is a more difficult situation. The charge cannot be terminated on a voltage. The capacity reached at 4.2 Volts per cell is only 40 to 70% of full capacity. For this reason you need to continue to charge until the current drops, and to terminate on the low current.

    It is important to note that trickle charging is not acceptable for lithium batteries. The Li-ion chemistry cannot accept an overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

    4. Charge temperature--must not be charged when temperature is lower than 0° C or above 45° C.

    5. Lithium Ion, or Li-Ion, uses a different charge algorithm. In this case, a constant current is supplied to the battery until the battery terminal voltage reaches 4.1 volts per cell. The charger then changes to a constant voltage source at 4.1 volts per cell, and the current tapers until it reaches 1/20 of the original constant current. The constant current, referred to as the bulk charge current is nominally set to the battery capacity divided by 2, and expressed in amperes. Assuming that 4.0 is the specified cell voltage.

    I also did some research on what "low standby power consumption" means for our Nokia chargers-the most reasonable theory I could relate to is if you leave your phone plugged in for an extended period of time the charger will trickle charge the phone as the phone discharges from just sitting there. So if this is the case then I stand corrected, there is no trickle charge going into the battery after the charge is complete, and/or the battery is fully charged.

    I am anxious to hear what data your EE friends come up with. :)
     
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  17. viewfly

    viewfly Mobile RF Advisor
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    I did get your curiousity up! Your info on Li-ion matches well with what I found too. The li-poly info you found confirms that they should be treated the same, regarding charging.

    I'm away this weekend, but I'll try my EE next week. It will be a little trick to access the dc wiring without damage, but perhaps I will try on an older transformer first.

    Some interesting info in this Thread.

    vf
     
  18. viewfly

    viewfly Mobile RF Advisor
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    That certainly is a confidence boost. I feel that Nokia must do the same thing, but the information is contradictory.

    Like Motos, Nokia's battery icon flashes while charging, then stops when the text 'charge completed' or 'battery full' displays. I can only think this means that the charging algorithm has stopped.

    If I leave the phone connected and use it, the icon will flash again for a bit, then stop. That indicates to me that the battery discharged a little and the charger topped it off.

    But after I make a meaurement of the current/voltage charging conditions, I'll be more convinced on what is going on, and whether to fully trust charging more than the recommended time. Either way, my experience with the car charger was good, and I kept the phone plugged in to the car everyday, without any great effect.

    Seems like what your doing is pretty safe.

    vf
     
  19. walkguru

    walkguru Wireless Guru
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    the only rule i have is never use a car charger. my battery's always last a long time.:browani:
     
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  20. charlyee

    charlyee Ultimate Insanity
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    If I were to venture a guess, I would say that statement is a carryover from the NiCad days. My SO's electric shaver has a rechargeable NiCad battery and the exact same caution is in the user manual.

    My IPAQ has a 1440mah, Li-ion battery and it basically stays in its cradle for atleast 9 hours a day. The cradle charges and syncs from the USB port of my laptop. That manual does not mention any caution about over charging.

    I also checked my LG 7000 and my SE Z520i manual and there is no mention of over charging in those manuals.
     
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  21. Jay2TheRescue

    Jay2TheRescue Resident Spamslayer
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    I used to hear that a lot, but I think as long as you are using an OEM car charger there is no problem. There may be an issue with cheap aftermarket ones though.

    -Jay
     
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  22. walkguru

    walkguru Wireless Guru
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    yeah, what i ment was, i no longer run it down, like in the past, and im sure your right, but thats the last rule from the ni-cad days.:browani:
     
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  23. bobolito

    bobolito Diamond Senior Member
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    Yes, I'm sure most wall chargers are just dumb AC/DC transformers with some noise filtering at most. However, I was referring to the phone itself as it has circuitry and intelligence (software) to control what comes in and out of the battery.
     
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  24. viewfly

    viewfly Mobile RF Advisor
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    I sat down with my EE friend and made some measurements with a ACp-7U Nokia charger and 3 nokia phones. That charger is rated for 3.7V and 350mA DC output.

    We opened one wire on the DC side and inserted an analog mA current meter to measure the current drawn by the phone. I observed that the phone's internal electronics is controlling the charge cycle with a specific charging algorithm.

    At the end of the cycle, ie 'charge complete', the current drawn drops sharply down to a steady 3 mA and remains there. That could be a trickle charge, or just the current drawn by the phone electronics that monitors the charge. We did not have the right set up to determine if that current was going to the battery or not.

    The phones were off, in all cases. Here what the cycle looks like:

    1) plugging into a partially discharged phone, the phone drew ~ 100 milliAmps. Not a steady current draw, but a on-off pulse between 20 - 100 mA, about 1 second duty cycle. Being DC and an analog current meter, this probably meant that the battery was drawing 100 mA and then zero. My EE friend thought that perhaps the electronics were making battery measurements during the off period.

    2) A few minutes later, the cycle swing went up to 200 - 350 mA. Again, probably meaning that the current drawn is pulsing on/off from zero to 350 mAmps.

    3) after a while, it remained somewhat steady at 350mA, with smaller current swings.

    4) During the 1/2 hour charge, the pulsed charging cycle slowing diminished downward, ie back down to 100-200 mA range, then down to 50mA and so on.

    5) When, 'charge complete' displayed, or the icon stopped flashing, the current drawn dropped right down to 3 mA and was rock steady. My impression was that the charge terminated. It remained at 3mA as long as the charger was connected. Again we don't know if this was a trickle or not.

    It was the same for all three Nokia phones.

    The next thing really surprised me.

    I disconnected the charger for 2 minutes and then reconnected. The battery was full charged, and off, but it started with the same charging cycle again: ie, taking the full 350mA charge again for minutes. Because the battery was really full, it only took about 10 minutes before it settled down to 3 mills again. Again the battery icon was blinking, indicating charging.

    So it seems leaving the charger in, it remains at the 3mA current draw, but when you dis and reconnect, it doesn't know this, and starts a high current charge over again, albeit for a shorter time. This can't be too good for the battery, if it is fully charged already. This would happen often with my car charger, since I would be in and out of the car.

    So if the residual 3 mA is not being fed to the battery, leaving it plugged in is ok. If it is being fed to the battery, that is not good. Also, don't charge your phone every 1/2 hour if not needed, nor let it drop to to full dead either. Rather, charging on some daily basis, with normal use of the phone performing a reasonable discharge, probably is a good balance between too much or too little charging of the phone. Only every 30 days or so, bring the battery to a full dead charge by normal use.

    The charging algorithm seems to follow a constant voltage and diminishing current monitoring electronics that shuts off the charging cycle when the current drawn by the battery reaches a minimum. See the chart below from the Electronics Design article:



    [​IMG]

    That's the best I could do. If I had to interpret Nokia's manual warning about not leaving the charger in, it would be this: Probably the phones charger electronics terminates the charging cycle completely, and the small non pulsing 3mA draw we measured is not going to the battery. The charging algorithm is on 'standy' and not consuming much power.

    So this is ok. However, if you leave the charger in (or constantly discount and reconnect during the day), and the phone on, normal power drain with the phone in standy, at some point will cause the charger cylce to start again, and this will pump a lot of current into an otherwise fully charged battery. That's not good. I've noticed this when I would charge my phone overnight: The phones display and 'beep' would wake me up several times during the night, saying that it's 'fully charged'. So perhaps this is part of Nokia's warning.

    just my guess.

    vf
     
  25. charlyee

    charlyee Ultimate Insanity
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    viewfly, very interesting and detailed findings & report, thank you. I did some experimenting on my own also. I managed to locate a 1amp meter and find a power cord that I could take apart. This was on my Motorola i325 IS and the rated output on the charger is 5VDC, 850mA.

    I measured 500mA at 5V while charging and
    ................241 mA at 5V at charge complete.

    As you can see the results are way different than yours, but I am not done yet, I plan on hooking up a test fixture and doing some more testingh hopefully over the weekend.....:)
     
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  26. viewfly

    viewfly Mobile RF Advisor
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    Wow, 241 mA at 'charge complete'! That's a lot of 'trickle' current for a 1450mAh battery.
     
  27. charlyee

    charlyee Ultimate Insanity
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    Really weird result, isn't it?

    The battery is rated at 3.6V, 1250mAh Lithium Ion. I am going to throw some diodes in the circuit to ensure that I am not reading any current flow out of the charged battery. In my case the 500mA was steady until it started to taper off, not the pulsing that you saw.
     
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  28. Jay2TheRescue

    Jay2TheRescue Resident Spamslayer
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    Speaking of batteries, The 22 year old gel-cell batteries in my recently acquired HERO jr will not take a charge (no suprise there). I was shocked as to how much they costed. I was going to go into my local Grainger showroom and buy replacements until I found out the batteries would cost me about $100. I just ordered new batteries from a surplus company I've done business with before for about $9 each, so I'll be up & running for under $40 once they arrive.

    -Jay
     
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  29. viewfly

    viewfly Mobile RF Advisor
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    A little googling around, and I learned that charging circuits for li-ion batteries are very complicated, beyond what I can fully understand.

    But pulse charging is one of the designs for various reasons. One being that it prevents the battery from overheating during the charge cycle.

    vf
     
  30. viewfly

    viewfly Mobile RF Advisor
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    For those interested, the abstract from an article on improvements in battery charging designs.

    By Jinrong Qian, Senior Member of Technical Staff, Texas Instruments
    Driven by integrated functionality and shrinking form-factors, the demand for portable devices such as cellular phones, PDAs and portable DVD players has grown significantly during the last few years. The power source has quickly become a bottleneck for advancing technology, and improvement of battery-power density cannot keep-up with demand. The lithium-ion (Li-Ion) battery is widely-adopted because of its high energy density on both a gravimetric and volumetric basis. To achieve longer system run-time and smaller size, more and more system designers are finding that improving a system’s power conversion efficiency with advanced circuit topologies is no longer sufficient. Battery charging has become another area to focus on for maximizing battery capacity and extending its service cycle-life. The linear charger is suitable for the low-capacity battery charge applications with its reasonable cost and small-size advantages. With the increasing power demand from portable devices, the linear battery charger no longer adequately meets charge requirements due to its high-power dissipation. This paper presents a MHz synchronous switching battery charger and design considerations to efficiently charge the battery and extend its cycle-life.

    From:http://www.powermanagementdesignlin...JVN?printableArticle=true&articleId=167100999
     
    #30 viewfly, Dec 12, 2006
    Last edited: Dec 12, 2006
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