- Charge your drill battery as usual. Remove the battery from the charger once fully charged. Leave the drill battery for several hours -- overnight is best. This lets energy discharge from your drill battery if it's not in good condition.
- Put your drill battery on a table and get your multimeter nearby. Read the label on the drill battery to find out the voltage and milliamp hours (mAh) it produces if the battery is in good condition.
- Look at the three terminals on the drill battery. One is labeled "Temp;" you don't need to use this terminal to test your drill battery. The second terminal is labeled "Gnd" and is the negative terminal. The third terminal is labeled "+ve" and is the positive terminal.
- Set the multimeter so it measures voltage. Place the metal prong on the end of the red wire from the multimeter onto the terminal labeled "+ve." Place the prong on the end of the black wire from the multimeter onto the terminal labeled "Gnd."
- Check the voltage measurement on the multimeter display. It reads the same as the output voltage on the drill battery label if the battery is fully charged and in good condition. Your drill battery is also fine if the multimeter measurement is about a volt lower than the drill battery label, but if the measurement is more than 1 volt lower your battery is losing its charge. Over time it gets worse so you need to check it regularly so you know when to get a replacement.
- Set the multimeter so it measures mAh. Place the metal prong on the end of the red wire from the multimeter onto the terminal labeled "+ve." Place the prong on the end of the black wire from the multimeter onto the terminal labeled "Gnd."
- Check the mAh measurement on the multimeter display. It reads the same as the mAh on the drill battery label if the battery is in good condition. Your drill battery is also fine if the multimeter measurement is about 5 percent lower than the drill battery label but if the measurement is more than 5 percent lower your battery is not producing the correct energy to power your drill and over time it will deteriorate further. Check it regularly so you know when to get a replacement.
How to Test a Drill Battery Pack With Three Terminals
Drill battery packs can contain nickel cadmium, nickel metal hydride, lithium ion or lithium polymer cells. Lithium ion and lithium polymer cells produce more energy and last longer, but they have to be monitored during the charging process as lithium-based cells can catch fire, or even explode, if they are overcharged. To prevent overcharging occurring, drill battery manufacturers fit temperature sensors that activate and cut off power if a battery gets too hot. You can determine if your drill battery has a temperature sensor as the battery pack has three, instead of two, terminals. However, you only need to use two terminals (positive and negative) to test your drill battery.
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