didnt charge enough?

Discussion in 'Acer Iconia Tab A500 Forum' started by xoluvsdance12, Aug 18, 2011.

  1. xoluvsdance12

    xoluvsdance12 Member

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    I just got my acer iconia today and when I set it up, I didn't read the directions first. I put it in the charger for around 2 hours then took it out and started to set it up. Later, I was looking through all the papers it came with and it said you have to charge it at least 4 hours the first time. Did I mess my battery up by not charging it enough?
     
  2. frnkws

    frnkws Member

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    I don't think so.
     
  3. sharpe351

    sharpe351 Member

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    If the battery is lith-ion, then you're ok. Just make sure the battery gets one full overnight charge asap. That way the device can learn the charge of the battery.

    Sent from my LG OP V using Tapatalk
     
  4. alphawave7

    alphawave7 Member

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    Nope. The cell was about 50% out of the box, so a few hours got it near full charge anyway. Be sure to fully charge and fully discharge the tab a few times in the coming days, as it helps calibrate the charge status being reported by the tab. :)
     
  5. StoneKy

    StoneKy Member

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    From the .pdf manual: 
     ​
    Rechargeable high density Li-polymer batteries: 3260 mAh x 2 (24.1 Wh)
     
  6. sharpe351

    sharpe351 Member

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    The only concern with Li-Po batteries is that they tend to explode, yes, I said explode when overcharged OR run completely down. Also they should never be run completely dead, because they cannot be revived. Your tablet should have safeguards built in to prevent this in either direction. I have lots of experience with this from racing remote control cars. These batteries go off like a stick of dynamite, but luckily, you'll have a smoky warning first.

    Sent from my LG OP V using Tapatalk
     
  7. Icebike

    Icebike Senior Member

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    Lets not spread FUD, OK?
    Any batteries you blew up were your own fault, (misuse).

    The ACER batteries all have built in protection in the charge circuit to prevent any such nonsense.
    The tablet will simply shut down long before the battery is totally discharged.
    The tablet can not be over charged, the circuit just takes it off line if you try.

    And another thing, @Alphawave7: You need no more than one discharge to the shutdown point followed by one full charge to calibrate the charge circuit. Li-Poly have no memory problems, but the Charge Controller needs to be calibrated by determining how low the battery can go. For calibrating the charge circuit, plug in the tablet when the Charge gets down to 5% or automatic shutdown, which ever happens first. Then charge it overnight. Do this once every other month. Most of the time it happens in normal usage, so you generally don't have to worry about this.

    You can safely ignore the warning "Its time to charge your tablet" because that warning comes at 15% in Android, but 15% is at least another hour or two of use before th 5% warning.

    Li-Poly does not suffer from partial discharges and frequent re-charges. But "Bump charging" will decrease your battery longevity.

    Bump charging is when you take the Acer off the battery just long enough to see the battery drop below 100% and then put it back on, hoping to trick the charge controller to pack in every last electron. Its a bad idea. Batteries often drop to 95% relatively quickly and then drop much more slowly.
    See this article.
     
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  8. xoluvsdance12

    xoluvsdance12 Member

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    Thanks everyone! So before I went to bed I plugged it into the charger at 40% :/ Then I let it charge overnight. Do you think if I let it discharge to 5% and then charge it overnight a few times the battery will still properly calibrate? Or is it too late? On my phone I dont usually worry about this stuff because I know I can always just get a new battery if it gets messed up, but I'm just extra worried about this because I dont think the batteries are replacable.
     
  9. sharpe351

    sharpe351 Member

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    Not entirely, but OK. Misuse, don't think so. Spent more than I would like to admit on special equipment to charge/maintain these batteries properly. Also take mental note that LiPo batteries get warm on discharge and cool slightly when charging/charged.

    These batteries have become waaay more stable over the past few years. Also the tabs have a lot more safeguards in place to prevent catastrophic failure. As opposed to what I did with racing.


    Sent from my LG OP V using Tapatalk
     
  10. Icebike

    Icebike Senior Member

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    Stop fretting about this.
    You did not damage anything and it is not "too late ".

    Just use your tablet and enjoy it. It is really not that sensitive to battery damage, you would really have to try very hard to damage this battery. The discharge recommendation doesn't do anything to the battery. It simply educates one of the chips in the tablet as to how low and how high the battery charge can go. Do it once. Then forget about it n

    There's nothing wrong with your battery.
     
  11. 2wheelsagain

    2wheelsagain Member

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    My tab usually gets charged over night a couple of times per week.
     
  12. alphawave7

    alphawave7 Member

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    This is correct for periodic calibration. We are talking about brand new cell packs here, which were fully charged (100%) without load at the fab to set initial SoC and SoH settings, then discharged to approx. 50% for shipping and final assembly into devices @ Acer's fab. New cells will benefit from several full charge/full discharge cycles as the chemistry/electrons establish their favorite routes (paths of least resistance-aka 'break-in') under real load (constant voltage-C rate), which indeed happens across most battery chemistries. Cell cycle efficiency actually IMPROVES initially, before they begin the dreaded degradation we are accustomed to. Overall cell life is one of the reasons many manuf. recommend a full charge (like OP mentions in the manual) initially, I suspect they also seek less service calls, so the peak voltage to calibrate the unit is also desireable. :) I agree that it's nothing for the OP to worry about.
     
  13. Spider

    Spider Administrator Staff Member

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    [h=1]Charging Lithium-ion[/h] Charging and discharging batteries is a chemical reaction, but Li-ion is claimed as an exception. Here, battery scientists talk about energies flowing in and out as part of ion movement between anode and cathode. This claim has merits, but if the scientists were totally right then the battery would live forever, and this is wishful thinking. The experts blame capacity fade on ions getting trapped. For simplicity, we consider aging a corrosion that affects all battery systems.
    The Li‑ion charger is a voltage-limiting device that is similar to the lead acid system. The difference lies in a higher voltage per cell, tighter voltage tolerance and the absence of trickle or float charge at full charge. While lead acid offers some flexibility in terms of voltage cut‑off, manufacturers of Li‑ion cells are very strict on the correct setting because Li-ion cannot accept overcharge. The so-called miracle charger that promises to prolong battery life and methods that pump extra capacity into the cell do not exist here. Li-ion is a “clean” system and only takes what it can absorb. Anything extra causes stress.
    Most cells charge to 4.20V/cell with a tolerance of +/–50mV/cell. Higher voltages could increase the capacity, but the resulting cell oxidation would reduce service life. More important is the safety concern if charging beyond 4.20V/cell. Figure 1 shows the voltage and current signature as lithium-ion passes through the stages for constant current and topping charge.
    [​IMG]
    Figure 1: Charge stages of lithium-ion. Li-ion is fully charged when the current drops to a predetermined level or levels out at the end of Stage 2. In lieu of trickle charge, some chargers apply a topping charge when the voltage drops to 4.05V/cell (Stage 4).
    Courtesy of Cadex
    The charge rate of a typical consumer Li-ion battery is between 0.5 and 1C in Stage 1, and the charge time is about three hours. Manufacturers recommend charging the 18650 cell at 0.8C or less. Charge efficiency is 97 to 99 percent and the cell remains cool during charge. Some Li-ion packs may experience a temperature rise of about 5ºC (9ºF) when reaching full charge. This could be due to the protection circuit and/or elevated internal resistance. Full charge occurs when the battery reaches the voltage threshold and the current drops to three percent of the rated current. A battery is also considered fully charged if the current levels off and cannot go down further. Elevated self-discharge might be the cause of this condition.
    Increasing the charge current does not hasten the full-charge state by much. Although the battery reaches the voltage peak quicker with a fast charge, the saturation charge will take longer accordingly. The amount of charge current applied simply alters the time required for each stage; Stage 1 will be shorter but the saturation Stage 2 will take longer. A high current charge will, however, quickly fill the battery to about 70 percent.
    Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Since the consumer market promotes maximum runtime, these chargers go for maximum capacity rather than extended service life.
    Some lower-cost consumer chargers may use the simplified “charge-and-run” method that charges a lithium-ion battery in one hour or less without going to the Stage 2 saturation charge. “Ready” appears when the battery reaches the voltage threshold at Stage 1. Since the state-of-charge (SoC) at this point is only about 85 percent, the user may complain of short runtime, not knowing that the charger is to blame. Many warranty batteries are being replaced for this reason, and this phenomenon is especially common in the cellular industry.
    Avoiding full charge has benefits, and some manufacturers set the charge threshold lower on purpose to prolong battery life. Table 2 illustrates the estimated capacities when charged to different voltage thresholds with and without saturation charge.

    Charge V/cell
    Capacity at
    cut-off voltage
    Charge time
    Capacity with full saturation
    3.80
    3.90
    4.00
    4.10
    4.20
    60%​
    70%​
    75%​
    80%​
    85%​
    120 min​
    135 min​
    150 min​
    165 min​
    180 min​
    65%​
    76%​
    82%​
    87%​
    100%​
    Table 2: Typical charge characteristics of lithium-ion. Adding full saturation at the set voltage boosts the capacity by about 10 percent but adds stress due to high voltage.
    When the battery is first put on charge, the voltage shoots up quickly. This behavior can be compared to lifting a heavy weight with an elastic band. The lifting arm moves up quickly but the weight lags behind. The voltage of the charging battery will only catch up when the battery is almost fully charged (see Figure 3. This charge characteristic is typical of all batteries.
    [​IMG]

    Figure 3: Capacity as a function of charge voltage on a lithium-ion battery
    The capacity trails the charge voltage, like lifting a heavy weight with an elastic band.
    Courtesy of Cadex
    Relying on voltage to read the available capacity during charge is impractical. The open circuit voltage (OCT) can, however, be used to predict state-of-charge after the battery has rested for a few hours. The rest period calms the agitated battery to regain equilibrium. Similar to all batteries, temperature affects the OCV. [BU- 903, How to Measure State-of-charge]
    Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.
    Once the charge is terminated, the battery voltage begins to drop, and this eases the voltage stress. Over time, the open-circuit voltage will settle to between 3.60 and 3.90V/cell. Note that a Li-ion battery that received a fully saturated charge will keep the higher voltage longer than one that was fast-charged and terminated at the voltage threshold without a saturation charge.
    If a lithium-ion battery must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge the battery and its protective circuit consume. The charger may kick in when the open-circuit voltage drops to 4.05V/cell and turn off again at a high 4.20V/cell. Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell. This reduces voltage-related stress and prolongs battery life.
    Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic load because it induces mini-cycles. The battery is continuously being discharged to 4.20V/cell and then charged by the device. The stress level on the battery is especially high because the cycles occur at the 4.20V/cell threshold.
    A portable device must be turned off during charge. This allows the battery to reach the set threshold voltage unhindered, and enables terminating charge on low current. A parasitic load confuses the charger by depressing the battery voltage and preventing the current in the saturation stage to drop low. A battery may be fully charged, but the prevailing conditions prompt a continued charge. This causes undue battery stress and compromises safety.
    Battery professionals agree that charging lithium-ion batteries is simpler and more straightforward than nickel-based systems. Besides meeting the voltage tolerances, the charge circuits are relatively simple. Limiting voltage and observing low current in triggering “ready” is easier than analyzing complex signatures that may change with age. Charge currents with Li-ion are less critical and can vary widely. Any charge will do, including energy from a renewable resource such as a solar panel or wind turbine. Charge absorption is very high and with a low and intermittent charge, charging simply takes a little longer without negatively affecting the battery. The absence of trickle charge further helps simplify the charger.
    [h=2]Overcharging Lithium-ion[/h] Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO[SUB]2[/SUB]). The cell pressure rises, and if charging is allowed to continue the current interrupt device (CID) responsible for cell safety disconnects the current at 1,380kPa (200psi).
    Should the pressure rise further, a safety membrane bursts open at 3,450kPa (500psi) and the cell might eventually vent with flame. The thermal runaway moves lower when the battery is fully charged; for Li-cobalt this threshold is between 130–150C°C (266–302°F), nickel-manganese-cobalt (NMC) is 170–180°C (338–356°F), and manganese is 250°C (482°F). Li-phosphate enjoys similar and better temperature stabilities than manganese.
    Lithium-ion is not the only battery that is a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly handled. Nickel-based batteries have also been recalled for safety concerns. Properly designed charging equipment is paramount for all battery systems.
    [h=2]Over-discharging Lithium-ion[/h] Li-ion should never be discharged too low, and there are several safeguards to prevent this from happening. The equipment cuts off when the battery discharges to about 3.0V/cell, stopping the current flow. If the discharge continues to about 2.70V/cell or lower, the battery’s protection circuit puts the battery into a sleep mode. This renders the pack unserviceable and a recharge with most chargers is not possible. To prevent a battery from falling asleep, apply a partial charge before a long storage period.
    Battery manufacturers ship batteries with a 40 percent charge. The low charge state reduces aging-related stress while allowing some self-discharge during storage. To minimize the current flow for the protection circuit before the battery is sold, advanced Li-ion packs feature a sleep mode that disables the protection circuit until activated by a brief charge or discharge. Once engaged, the battery remains operational and the on state can no longer be switched back to the standby mode.
    Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week. Copper shunts may have formed inside the cells that can lead to a partial or total electrical short. If recharged, the cells might become unstable, causing excessive heat or showing other anomalies. Li-ion packs that have been under stress are more sensitive to mechanical abuse, such as vibration, dropping and exposure to heat.
    [h=2]Charging Lithium-ion Polymer[/h] Charging Li‑ion polymer, also referred as Li-polymer, is very similar to a regular lithium-ion battery and no changes in algorithm are necessary. Most users won’t even know if their battery is Li‑ion or Li‑polymer. The word “polymer” has been used as promotional hype and does not reflect special attributes other than to know that the battery is built in a different way to a standard Li-ion.
    Most polymer batteries are based on a hybrid architecture that is a cross between Li-ion and Li-polymer. There are many variations within the polymer family, and the true dry polymer battery for the consumer market is still years away. Also know as the “plastic battery,” this system was first announced in early 2000 but was never able to attain the conductivity needed for most applications at ambient temperatures. Read more about the Lithium-polymer battery and the Pouch Cell.
    [h=2]Simple Guidelines for Charging Lithium-based Batteries[/h]
    • A portable device should be turned off while charging. This allows the battery to reach the threshold voltage unhindered and reflects the correct saturation current responsible to terminate the charge. A parasitic load confuses the charger.
    • Charge at a moderate temperature. Do not charge below freezing.
    • Lithium-ion does not need to be fully charged; a partial charge is better.
    • Chargers use different methods for “ready” indication. The light signal may not always indicate a full charge.
    • Discontinue using charger and/or battery if the battery gets excessively warm.
    • Before prolonged storage, apply some charge to bring the pack to about half charge.
    • Over-discharged batteries can be “boosted” to life again. Discard pack if the voltage does not rise to a normal level within a minute while on boost.
    Charging Lithium-ion – Battery University
     
  14. alphawave7

    alphawave7 Member

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    Despite my natural reluctance to rely on a sole source, Isadore has been my go-to guy for years on this subject, and I find MANY other sources rely (paraphrase as well as outright plagiarise) on him as well. This is also a useful article, despite the fact it covers several chemistries and was written about a decade ago (many of his articles are, btw.):
    http://www.buchmann.ca/chap6-page1.asp
    :
    )
     
    Last edited: Aug 21, 2011
  15. Spider

    Spider Administrator Staff Member

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    @AW7 With that to read, I didn't need to DL my free Friday book from B&N this week.:rolleyes:
     

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