How to Repair a Laptop Battery

Most laptop batteries are smart. This means that the pack consists of two parts: the chemical cells and the digital circuit. If the cells are weak, cell replacement makes economic sense. While nickel-based cells are readily available, lithium-ion cells are commonly not sold over the counter, and most manufacturers only offer them to authorized pack assemblers. This precaution is understandable given liability issues. Read also about Safety Concerns and Protection Circuits. Always use the same chemistry; the mAh rating can vary if all cells are replaced.

A laptop battery may have only one weak cell, and the success rate of replacing the affected cell depends on the matching with the others. All cells in a pack must have a similar capacity because an imbalance shortens the life of the pack. Read more about Can Batteries Be Restored?. Furthermore, the state-of-charge of all cells being charged for the first time should have a similar charge level, and the open-circuit voltages should be within 10 percent of each other. Welding the cells is the only reliable way to get dependable connection. Limit the heat transfer to the cells during welding to prevent excess heat buildup.

The typical SMBus battery has five or more battery connections consisting of positive and negative battery terminals, thermistor, clock and data. 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 one-wire system combines clock and data.) For safety reasons, a separate thermistor wire is brought to the outside. Figure 1 illustrates a battery with six connections.

Some batteries are equipped with a solid-state switch that is normally in the “off” position and no voltage is present on the battery terminals; connecting the switch terminal to ground often turns the battery on. If this does not work, the pack may need a proprietary code for activation, and battery manufacturers keep these codes a well-guarded secret.

How can you find the correct terminals? Use a voltmeter to locate the positive and negative battery terminals and establish the polarity. If no voltage is available, a solid-state switch in the “off” position may need activating. Connecting 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 appears, the battery may be dead or the pack will require a security code. The 100-Ohm resistor is low enough to engage a digital circuit and high enough to protect the battery against a possible electrical short.

Establishing the connection to the battery terminals should now enable charging. If the charge current stops after 30 seconds, an activation code may be required, and this is often difficult if not impossible to obtain.

Some battery manufacturers add an end-of-battery-life switch that turns the battery off when reaching a certain age or cycle count. Manufacturers argue that customer satisfaction and safety can only be guaranteed by regularly replacing the battery. Such a policy tends to satisfy the manufacturer more than the user, and newer batteries do not include this feature.

If at all possible, connect the thermistor during charging and discharging to protect the battery against possible overheating. Use an ohmmeter to locate the internal thermistor. The most common thermistors are 10 Kilo Ohm NTC, which reads 10kΩ at 20°C (68°F). NTC stands for negative temperature coefficient, meaning that the resistance decreases with rising temperature. In comparison, a positive temperature coefficient (PTC) causes the resistance to increase. Warming the battery with your hand may be sufficient to detect a small change in resistor value when looking for the correct terminal on the battery.

In some cases the chemical battery can be restored, but the fuel gauge might not work, is inaccurate, or will provide wrong information. After repackaging, the battery may need some sort of initialization/ calibration process. Simply charging and discharging the pack to reset the flags might do the trick. A “flag” is a measuring point to mark and record an event.

 The circuits of some smart batteries must be kept alive during cell replacement. Disconnecting the voltage for only a fraction of a second can erase vital data in the memory. The lost data could contain the resistor value of the digitized shunt that is responsible for the coulomb counter. Some integrated circuits (IC) responsible for fuel gauge function have wires going to each cell, and the sequence of assembly must to be done in the correct order.

To assure continued operation when changing the cells, supply a secondary voltage through a 100-Ohm resistor to the circuit before disconnection and remove the supply only after the circuit receives voltage again from the new cells. Cell replacement of a smart battery has a parallel with open-heart surgery, where doctors must keep all organs of the patient alive.

Anyone repairing an SMBus battery needs to be aware of compliance issues. Unlike other tightly regulated standards, the SMBus allows some variations, and this can cause problems when matching laptop battery packs with existing chargers. The repaired SMBus battery should be checked for compatibility before use.

What Should I Consider When Buying a Laptop Battery?

When choosing a laptop battery, you should first make sure that it is compatible with your computer, and then consider the materials it's made out of. It's also best to look at the power rating and service life, since these have a large impact on its performance and lifespan. Additionally, you may want to consider whether you want a brand name or generic replacement, as well as whether you want a new battery or a refurbished one. Whichever one you choose, you should also look at any warranties offered, and make sure that it complies to safety standards.

Compatibility

The first thing to look for when buying a new laptop battery is compatibility with your computer. Most are made to work with specific models of computers, and have this information listed in their product descriptions. To make sure that one will work with your computer, you'll need to know the make and model number of your laptop; if you don't know this offhand or don't have the necessary paperwork, check the inside of your laptop's battery compartment while it is off and unplugged. You may also find the part number of the battery, located on its casing.

You should also consider the material that the battery is made out of: Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH), Lithium Ion (LiON), or Lithium Ion Polymers (Li-Poly). NiCad batteries are largely obsolete, since they are very heavy and don't last very long. NiMH batteries last longer than NiCads, but significantly shorter than LiONs and Li-Polys. They also weigh more, and have the "memory effect," which causes them to lose the ability to fully recharge.

Generally speaking, LiON and Li-Poly batteries are the best choice, as long as they're compatible with your laptop, since they are light, last longer than NiMHs, and are about a third lighter. They also charge more quickly, and are also more environmentally friendly. Regardless of which type of laptop battery you end up getting, you should make sure that the cells are manufactured in such a way that they meet international standards of laptop battery safety, like those designated by Underwriters Laboratories (UL).

Capacity

The capacity, or power rating is another important consideration. This is the amount of power that the battery can produce, and is usually written in milliamperes (mAh). The greater the capacity, the longer the battery can run before it needs to be recharged, so look for the highest mAh number. Most new ones are rated to at least 5,000 mAh.

Service Life

Like other technological products, laptop batteries have a designated service life — the length of time that they're expected to work optimally. This is usually written in terms of cycles, with one cycle consisting of completely running the battery out, and then completely charging it again. Most are are able to go through between 300 and 1,500 charging cycles, and can be used after the maximum cycle count is reached, but may not hold a charge as well. Some computers come with a cycle counter built in, but there is free cycle counting software is also available online for download.

Branded vs. Unbranded

You may additionally want to consider whether you want to buy a brand name laptop battery, like the one your laptop came with, or a generic replacement one. Many brand companies and companies that make generic batteries get their components from the same manufacturers, so it may not make a huge difference, but some brand name versions meet more rigorous safety standards than generic ones, and some do use different, higher quality components. Also, some brand name versions come with better warranties than generic ones. Branded batteries do tend to be more expensive than generic ones though, so if you compare a brand name laptop battery and a generic one and find them to be largely similar, then you may want to go with the generic one.

New vs. Refurbished

Besides the issue of branding, you should also think about whether you want a new laptop battery or a refurbished one. Though some refurbished ones are very good and are often much cheaper than new ones, it's a little risky to buy refurbished, since you don't really know how old the battery is, and it may die suddenly. Also, many refurbished batteries don't come with very good warranties, so it may be worth it to just get a new one, especially if you use your laptop a lot.

How to Choose and Mount a CPU Fan: Everything You Need To Know

Are you looking to mount a new CPU fan? Finding the right CPU fan requires a great deal of research. Not only do different fan sizes populate the market, a byzantine maze of CPU socket types, bearing technologies, fan speeds and more greatly complicate the selection process. Fortunately, you’ve come to the right place.

This how-to guide explains the nitty-gritty of getting the right fan and mounting it to your PC’s CPU. Additionally, it explains my favorite method for applying thermal compound to a CPU.

If you’re simply looking for installation instructions on how to mount a CPU fan, skip to the second part of this article.

What Kind of CPU Fan Do You Need?

The PC component that keeps your CPU cool consists of two separate parts – the heat sink, which is typically a block of metal, designed to maximize airflow and surface area. The second part is the fan. Together they’re commonly referred to as the heat-sink/fan combo or HSF, for short. Lots of technologies and aftermarket products exist. Some are designed to reduce noise while others are designed for maximum cooling. All of them, however, require you know a few things about your computer.

Determining what sort of CPU fan you need takes five steps.

• First, find your motherboard’s CPU socket.
• Second, measure the available height in your case between the top of the CPU and the panel of the computer’s chassis.
• Third, inspect the area on your motherboard surrounding the CPU socket.
• Fourth, determine how fast you want the fan to run.
• Fifth, find the Thermal Design Power (TDP) of your CPU, if you are not using the stock (the one that comes with the CPU) HSF combo. TDP is the heat output of your CPU, measured in watts.

How to Install CPU Fan

The Central Processing Unit or CPU is the component of a computer that processes all information and also known as the computer processor. The processor tends to heat up when being used. The processor tends to melt or break down when the heat produced is not dissipated. The CPU fan cools the computer’s processor and prevents it from breaking down. For better cooling function, the CPU fan is installed with a heat sink. A heat sink is a metallic device that attaches directly to the CPU, drawing away the heat of the CPU through its aluminum fin-like structure. CPU fans, along with heat sinks, come in a wide variety of designs and sizes. Most new processors come with their own CPU fan and heat sink.

Step 1

Choose an appropriate CPU fan and heat sink. If the processor does not come with its own CPU fan and heat sink, a fan appropriate for the processor must be bought. The fan appropriate to the computer may be seen on the computer’s manual. The available space inside the computer’s casing must be taken into consideration when installing a CPU fan.

Step 2

Shut down the computer and open the casing so that the CPU is exposed. Set aside screws, clips, and the cover for the CPU.

Step 3

Affix the CPU fan to its heat sink. This may have already been done. If the fan has not been attached, carefully fasten the fan and heat sink together by using the screws that came with the device.

Step 4

Attach the heat sink and fan to the CPU. The method of attaching the heat sink and fan to your CPU differs for CPU, CPU fan, and heat sink. A thin layer of heat sink compound may be spread on the CPU’s surface to ensure contact. Some fans and heat sinks attach to the CPU chip with a number of clips. Attach the fan gently with an even amount of force. Make sure not to damage the CPU and the motherboard of the computer.

Step 5

Connect the power cable of the heat sink and fan combination to the 3-pin power lead found on the computer’s motherboard. Search for a label 'fan' or 'CPU fan.'

Step 6

Replace computer cover and test the CPU fan.