Due to the lower cost and better performance of non-volatile memory, it is now a common feature of microcontrollers. This reduces the need for batteries to provide backup power to low-power static RAM in modern equipment. Nevertheless, batteries remain common in older equipment and may last as long as two decades. This article provides a good example of how to approach battery replacement. Here are some tips regarding battery replacement in computers, radios, or lab equipment.
Before Replacing the Battery
- Be sure you have the right battery type, including case dimensions, terminal voltage, and pin placement (if any). Battery manufacturers can often provide a cross-reference, even on obscure parts that are no longer available. The equipment manufacturer may also have information on the batteries.
- Make a record of all equipment configuration settings since removing the battery may cause those memory locations to be reset to factory defaults.
- If possible, obtain a copy of the equipment’s initial power-up and operation instructions. Any special settings or activation sequences may have to be repeated after replacing the battery.
- Before attempting to actually replace the battery, be sure the equipment is truly off! Uninterruptable power supplies or even larger batteries may be present. Disconnect them to avoid working on a live circuit.
Getting to the Battery
- It is often difficult to get to or work on backup batteries since they weren’t intended to be replaced frequently, if at all. As you dig into the equipment, take careful notes of any special techniques or order-of-work that might affect how the equipment goes back together. If practical, place mounting screws and other hardware associated with a specific module or circuit board in a sandwich bag and label it.
- Take photos and make drawings of the internal PC boards and assemblies before you move or remove them. This is the time to make notes about which cables go where and how connectors are oriented.
Removing the Battery
- Coin cells and cylindrical cells that aren’t soldered in can be pried out of their holders. I recommend a plastic tool that won’t accidentally short terminals together. Even a mostly-discharged battery can have enough energy left to burn a small trace or component.
- If the battery has leaked and corroded the holder terminals, this discussion on RadioReference may be helpful. Use as little cleaning solution as possible and use clean water to remove any solution left on the PC board or holder terminals. Dry the area afterward with a hair dryer.
Installing the Replacement Battery
- If you have the equipment manual, check for and follow special measures or procedures that may be required when replacing the battery.
- Avoid using metal pliers or screwdrivers to hold or push the battery. An accidental short, even temporary, can damage or discharge the battery.
- If the battery terminals are connected with individual terminals, reconnect them starting with the terminal connected to circuit ground.
- A slip of paper between a holder tab or clip and the battery can act to prevent the battery from being prematurely connected to the circuit. Leave enough paper to pull the slip out after the battery is installed.
- If the new battery is soldered in or a new holder is soldered in, remove any flux left and thoroughly clean around the mounting pads with alcohol or flux remover or contact cleaner. This avoids creating a leakage path that can gradually discharge the battery.
