2013-04-05


Tips on how to Repair a Laptop Battery

Most laptop batteries are smart. Which means the rest is made of two parts: mit cells as well as the digital circuit. If the cells are weak, cell replacement makes economic sense. While nickel-based cells are all around, lithium-ion cells may be not sold non-prescription, and quite a few manufacturers only offer these to authorized pack assemblers. This precaution is understandable given liability issues. Read also about Safety Concerns and Protection Circuits. Use the identical chemistry; the mAh rating may differ if all cells are replaced.

A laptop battery may have only one weak cell, plus the recovery rate of replacing the affected cell depends upon the matching with the others. All cells in a pack will need to have a comparable capacity because an imbalance shortens the life with the pack. Find out more about Can Batteries Be Restored?. Furthermore, hawaii-of-handle of all cells being charged the very first time should have the same charge level, along with the open-circuit voltages ought to be within 10 % of each other. Welding cellular matrix will be the only reliable way of getting dependable connection. Limit the heat transfer towards the cells during welding to counteract excess heat buildup.


The typical SMBus battery has five or more battery connections including things like positive and negative battery terminals, thermistor, clock and data. The connections are sometimes unmarked; however, the positive and negative may be located for the outer edges from the connector as well as the inner contacts accommodate the clock and data. (One-wire system combines clock and data.) For safety reasons, another thermistor wire is taken to the outer. Figure 1 illustrates an assortment with six connections.

Figure 1: Terminal connection of a typical laptop battery

The negative and positive terminals are usually designed into the surface; no norm exists about the arrangement on the other contacts.
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Some batteries come with a solid-state switch that is normally in the “off” position with no voltage exists on the
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  •  terminals; connecting the switch terminal to ground often turns the battery on. Detail does not work, those might require a proprietary code for activation, and battery manufacturers keep these codes a highly-guarded secret.
    How could you find the proper terminals? Work with a voltmeter to locate the positive and negative battery terminals and establish the polarity. If no voltage is available, an excellent-state switch within the “off” position could need activating. Connecting the voltmeter towards outer terminals, create a 100-Ohm resistor (other values could also work), tie one end to ground, for a other end touch each terminal while observing the voltmeter. If no voltage appears, the battery may be dead or perhaps the pack will demand a burglar alarm code. The 100-Ohm resistor is low enough to engage be sure you circuit and high enough to defend the battery against a potential electrical short.
    Establishing the text towards battery terminals should now enable charging. In the event the charge current stops after a few seconds, an activation code might be required, and this is often difficult if not impossible to acquire.

    Some battery manufacturers add a stop-of-battery-life switch that turns it off when reaching some age or cycle count. Manufacturers conisder that client satisfaction and safety are only able to be guaranteed by regularly replacing battery. This kind of policy is likely to satisfy the manufacturer more than the person, and newer batteries don't include this feature.

    Whenever possible, connect the thermistor during charging and discharging to defend it against possible overheating. Use an ohmmeter to uncover the interior thermistor. The commonest thermistors are 10 Kilo Ohm NTC, which reads 10kΩ at 20°C (68°F). NTC represents negative temperature coefficient, which means the resistance decreases with rising temperature. When compared, a confident temperature coefficient (PTC) causes the potential to deal with increase. Warming battery with your hand may be sufficient to detect a small alteration of resistor value when evaluating the best terminal on the battery.

    Sometimes caffeine battery could be restored, nevertheless the fuel indicator might not work, is inaccurate, or provides wrong information. After repackaging, it may require some kind of initialization/ calibration process. Simply charging and discharging the rest to reset the flags might do just as well. A “flag” is usually a measuring point to mark and record opertation.

     The circuits of some smart batteries has to be kept alive during cell replacement. Disconnecting the voltage for only a fraction of a second can erase vital data within the memory. The lost data could support the resistor price of the digitized shunt that is certainly liable for the coulomb counter. Some integrated circuits (IC) accountable for fuel gauge function have wires planning to each cell, along with the sequence of assembly must to become done in the right order.

    In order to guarantee continued operation when changing the cells, supply a second voltage by having a 100-Ohm resistor towards circuit before disconnection and remove the availability only following your circuit receives voltage again from your new cells. Cell replacing a smart battery incorporates a parallel with open-heart surgery, where doctors must keep all organs of the patient alive.

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