What Does This Error Mean?

An APC UPS battery not charging is usually caused by a battery that has aged past the point of accepting a charge. If the battery is less than 3 years old and still will not charge, the UPS charging circuit may have developed a fault.

Affected Models

APC Back-UPS series
APC Back-UPS Pro series
APC Smart-UPS series
All APC UPS models

Common Causes

Battery end of life — depleted cells refuse to accept a charge
Battery deeply discharged below the recovery threshold — not recoverable without replacement
Charging circuit fault in the UPS after a power surge or overload event
Battery terminals loose or corroded inside the battery compartment
Incorrect replacement battery installed — wrong voltage or capacity

How to Fix It

Check battery age.

APC sealed lead-acid batteries typically last 3–5 years. If the battery has not been replaced in this period, failure to charge is the expected end-of-life symptom. Replace with the correct RBC-numbered battery cartridge for your APC model.
Inspect battery terminals for corrosion.

Open the battery compartment and inspect the battery terminals. White or blue powdery residue on the terminals is corrosion and prevents good electrical contact. Clean terminals gently with a dry cloth and reconnect firmly.
Allow 24 hours for a depleted battery to begin recovering.

A deeply discharged battery may take several hours before the charging circuit detects enough voltage to begin a full charge. Leave the UPS plugged in and powered on for 24 hours before concluding the battery is not charging.
Test with a replacement battery.

Install a confirmed-fresh APC replacement battery cartridge. If the new battery charges normally, the original battery had failed internally. If the new battery also does not charge after 24 hours, the UPS charging circuit has a fault.
Check for a fault LED indicator.

APC UPS units with a fault LED will show a charging fault with the indicator on or flashing. Consult your model's user manual for the fault LED pattern meanings. A charging fault LED with a new battery installed confirms an internal circuit problem.

When to Call a Professional

If a brand-new APC replacement battery cartridge does not charge after 24 hours, the internal charging circuit is faulty. The UPS will need professional service or replacement.