Computers rely on a CMOS battery to maintain a small electrical charge to keep the BIOS information and date and time current when the power is turned off or the computer is disconnected from power. Modern computers have small coin-cell batteries that perform this function and that are located on the motherboard in sockets that allow for easy battery replacement. Older systems, such as Packard Bell 486 computers, often used what became known as barrel batteries, which were batteries that were soldered in place using two or three leads attached directly to the motherboard. These batteries require careful soldering techniques to replace.
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Things you need
- Replacement barrel battery
- Electronic soldering iron
- Soldering wick or solder suction pump
- Anti-static wrist strap
- Screwdriver set
- Small set of clip-on soldering heat sinks
Attach a soldering heat sink to each leg of the battery about halfway between the battery and the motherboard. Preheat the soldering iron and trim the end of the soldering wick to provide a fresh, clean copper surface for the molten solder to adhere to, or prime the solder suction pump if that is what is being used to remove the solder.
Apply the soldering iron directly to the tip of the lead from the battery on the backside of the motherboard where the lead protrudes through the board. Apply the soldering wick to the solder holding the lead in place, allowing it to soak up the solder as it melts, or apply the soldering suction pump for about 5 to 10 seconds to avoid overheating the motherboard. Repeat this operation two more times to get as much solder as possible out of the hole from the backside of the board.
Flip the board over and use the same technique to remove solder from the front side of the motherboard, heating the lead near the motherboard and staying as far away from the battery as possible, taking only three to five seconds each time. Repeat this operation on both sides of the board until the solder is removed and the lead pulls out of the board easily. Then repeat for the other leads until the battery is free. Remove any excess solder that still remains in the hole after the battery is removed.
Attach the soldering heat sinks to the battery leads about halfway up each lead. Insert the battery into the motherboard according to the orientation for positive and negative as marked on the board and the battery.
Heat the junction of the lead and the hole with the soldering iron while applying the tip of the solder to the lead and the hole until the solder melts and fills the hole. Then remove the heat and detach the excess solder from the hole. Repeat this procedure for the other leads, being careful not to apply too much or too little solder to any of the holes but just enough to fill the hole and hold the lead in place.
Inspect the solder connections and remove the solder and retry any connection that doesn't look like it will hold the lead or looks like it doesn't provide a good connection between the lead and the hole. Remove the heat sinks from the battery and inspect for any solder that may have run across the circuit board or any heat-related damage that may have occurred.
Tips and warnings
- It is often easier to replace motherboards than use the obsolete barrel battery rather than to replace the battery, as the motherboard must be removed from the system anyway. Packard Bell 486 systems that require a barrel-style battery can be run without a battery installed, but the CMOS date and time, as well as hard drive configuration information, must be entered each time the system boots from a power-off state.
- Remove corroded batteries by cutting the leads rather than using heat, which may further damage the battery or cause a fire. Then follow these steps to remove the leads and prepare the holes for the new battery. Motherboards are sensitive to static electricity and an anti-static wrist strap should be used while working on them to avoid damaging components. Excess heat will damage the motherboard, battery and surrounding components.
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