Why does the “C-End” (charge end) message appear on the secondary display even though the bar indicator does not display a complete full bar? Is there something wrong with the battery?
When the “C-End” (charge end) message is displayed on the secondary display, it actually indicates that the battery is fully charged. To further explain on the bar indicator, refer to the table below:
U1252A can operate on either a 9V alkaline battery or a 7.2V NiMH rechargeable battery . In standby (SBY) mode, if a 9V alkaline battery is used, the bar indicator will display full bar or 100%. When a 7.2V (rechargeable) fully charged battery is used, the bar indicator will display ~ 80%  of the full bar. This is because the 7.2V rechargeable battery typically able to charge up to 8.4V max .
During charging or C-End mode, when a 7.2V (rechargeable) battery is fully charged, the bar indicator will display ~ 42.8%  of the full bar (as show in the figure above).
Therefore, this situation, whereby the “C-End” message is displayed even though the battery bar indicator is not full, does not indicate that the battery is faulty. It actually indicates the actual capacity of the U1252A battery.
1. SBY (Standby mode) or normal operating condition.
2. Keysight supplies 7.2V NiMH rechargeable battery as part of standard accessories to U1252A.
3. This is based on the calculation (8.4V-6V)/ (9V-6V) *100%= 80%.
4. Based on the battery supplier datasheet, 7.2V battery (nominal type) can be charged up to 8.4V (max).
5. This is based on the calculation (8.4V-7.2V)/ (10V-7.2V) *100%=42.8%.
More information on the recommended battery type, please refer to this FAQ: What is the recommended battery type for the U1251A, U1252A and U1253A Handheld Digital Multimeters (DMM)?