When encountering Error 02000 on an APC UPS system, the following troubleshooting steps can be undertaken:
The unit may stop charging the batteries entirely.
Further reading / resources
Heat is the enemy of DC-DC converters. Keep your UPS ambient temperature below 77°F (25°C). For every 15°F above that, battery life halves, and MOSFET failure rates triple.
In the architecture of professional-grade APC Smart-UPS systems (particularly the SRT and SURT series), is categorized as a critical power system fault. apc ups power system error 02000 link
The internal board that replenishes the battery bank has suffered a component failure.
If you have reseated the hardware and updated the firmware but the error persists, the internal communication board (interface board) may be physically damaged. Contact APC Support (Schneider Electric) and provide them with the specific error code (02000) and the serial number of the unit. When encountering Error 02000 on an APC UPS
The inverter uses switching transistors (IGBTs in larger units, MOSFETs in smaller ones). If one fails as a short circuit, the UPS detects back-feed voltage during self-test, immediately throwing error 02000.