![]() ![]() The most common thermistors are 10 Kilo Ohm NTC, which reads 10kΩ at 20C (68F). Use an ohmmeter to locate the internal thermistor. ![]() If at all possible, connect the thermistor during charging and discharging to protect the battery against possible overheating. Mind you, such a policy also rotates inventory. They argue that customer satisfaction and safety can only be guaranteed by regularly replacing the battery. Some battery manufacturers add an end-of-battery-life switch that turns the battery off when reaching a certain age or cycle count. If the charge current stops after 30 seconds, an activation code may be required. The 100-Ohm resistor is low enough to engage a digital circuit and high enough to protect the battery against a possible electrical short.Įstablishing the connection to the battery terminals should now enable charging. If there is no response, then it is possible that the battery is dead or locked by a code. Repeat by tying the resistor to a positive voltage potential. Connect the voltmeter to the outer terminals, take a 100-Ohm resistor (other values may also work), tie one end to ground and with the other end touch each terminal while observing the voltmeter. If no voltage is present, a solid-state switch may be in the “off” position and needs activating. Use a voltmeter to locate the positive and negative battery terminals and establish the polarity. Battery manufacturers keep these proprietary codes a well-guarded secret to which even service personnel have no access. If this does not work, the pack may need a code for activation. Connecting the switch terminal to ground or pulling it up often turns the battery on. Some batteries are equipped with a solid-state switch that is normally in the “off” position and no voltage is present at the battery terminals. The positive and negative terminals are usually placed on the outside no norm exists on the arrangement of the other contacts. Figure 1 illustrates a battery with six connections.įigure 1: Terminal connection of a typical laptop battery (The one-wire system combines clock and data.) For safety reasons, a separate thermistor wire is brought to the outside. The connections are often unmarked however, the positive and negative are commonly located at the outer edges of the connector and the inner contacts accommodate the clock and data. The typical SMBus battery has five or more battery connections consisting of positive and negative battery terminals, thermistor, clock and data. Most laptop batteries are smart and consist of the “chemical battery” that is managed by the “digital battery.” A common protocol is the System Management Bus, better known as SMBus.
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