If you have charging issues with your 500 series instrument, there are a few things that can be looked at. First of all, there are some older versions of firmware where the instrument may go into a "trickle charge". If you are having charging issues, unplug the device from the power supply. Turn the instrument off by pushing the battery saver button on the bottom of the unit. Wait about 10 seconds, then plug the unit back in to the power supply. After doing this, make sure you keep the unit plugged in for at least 3 hours uninterrupted, not pushing any buttons or taking readings or anything. In some cases this will solve the problem.
If this does not work, the power supply may be at fault. Check the power supply with a voltmeter and see if you are getting the correct voltage from the power supply. If not, you may need a new power supply.
Note: If the instrument does not go into the 'Sleep'mode'; meaning when unplugged from the charger, the display will turn off after 120 seconds; then your instrument will need to be serviced.
If the power supply is getting enough voltage, it is more than likely the battery. Plug in the unit so you can get power to the unit. From the main menu, go to Configuration and hit the Enter Key (bottom right hand key). From the Configuration, select Display and hit your Enter key again. Scroll down to Battery Status and hit your Enter key again.
Idle: The Idle voltage is the voltage of the battery pack taken at the moment the battery status menu was entered. A completely charged battery should measure around 5.9v to 6.1v while a completely dead battery should measure around 4.7v to 4.9v.
Measure: The measure voltage is the voltage of the battery pack just after the last successful measurement. It should not be more than .8 to 1.0 volts different than the idle voltage. If you have more than 1.0v after a full charge, it's either a bad battery pack or the power board in the instrument.
Charger: The charger voltage is the voltage of the power supply if one is plugged in. The 500 series instruments can be shipped with one of two different power supplies. The original power supply P/N SE30-81(no longer available), which will display around 14v to 18v with no load applied. The multi switching power supply, P/N SE30-177 will display around 11.5v to 12.5v with no load applied. If no power supply is plugged in or the power supply is bad and not delivering any voltage, it will display around .7v.