Battery Backup Maintenance
Updated February 20, 2026
Power outages and heavy storms go hand in hand. The electricity goes out, the primary sump pump stops, and water keeps rising. That's exactly when your battery backup needs to work. The catch is, backup batteries degrade silently -- they'll show a green light right up until the moment they can't hold a charge. Regular testing is the only way to know.
Overview
Power outages and heavy storms go hand in hand. The electricity goes out, the primary sump pump stops, and water keeps rising. That's exactly when your battery backup needs to work. The catch is, backup batteries degrade silently -- they'll show a green light right up until the moment they can't hold a charge. Regular testing is the only way to know.
What to Know
Step by Step
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Check the battery charge level
Most backup systems have a status display or LED indicators showing battery charge. A fully charged battery should read 12.6-12.8 volts with a multimeter. Below 12.0 volts means the battery isn't holding a charge -- replacement time.
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Test the backup pump
Unplug the primary pump from the outlet. Pour water into the sump pit until the backup activates. Verify the backup pump moves water out and the discharge is clear. Time how long it takes to pump down -- compare to previous tests. Slower pump-down times indicate a weakening battery or pump.
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Inspect the charger
Make sure the trickle charger is plugged in and the indicator light shows it's charging. Check the connection between the charger and battery for corrosion. Clean battery terminals with a wire brush if there's white or green buildup.
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Check battery water level (if applicable)
Standard lead-acid batteries need distilled water added to the cells periodically. Remove the caps and check -- the water level should cover the lead plates. Top off with distilled water only, never tap water. AGM and sealed batteries skip this step.
Pro Tips
- Write the battery installation date on the battery with a marker. Replace every 3-4 years regardless of test results.
- Test the backup before storm season -- spring and fall at minimum.
- Keep a spare battery. When the power goes out during a storm, stores are closed and delivery takes days.
- A battery backup alarm that beeps when the backup activates alerts you even when you're asleep.
Mistakes to Avoid
- Assuming the green light means the battery is good. It only means the charger is connected, not that the battery has capacity.
- Waiting until the battery fails during a storm to replace it.
- Not testing the backup pump itself -- the battery can be fine but the pump can fail.
- Using a car battery instead of a deep-cycle marine battery. Car batteries aren't designed for the slow, repeated discharge that backup pumps require.
When to Call a Pro
If the backup system isn't charging, the pump won't activate, or you need to install a new backup system, a plumber or electrician can set it up. If you're considering a water-powered backup, a plumber needs to connect it to your water supply and configure the venturi pump.
Bottom Line
Test the backup quarterly, check the battery voltage, and replace the battery every 3-4 years. A $150 battery replacement every few years is trivial compared to a flooded basement during a power outage.