PLC storage of lithium batteries, the voltage is lower than 3V to replace the battery.
When the PLC user program to retain in the RAM, it will use the battery, the battery is usually 3V or 3.6V non-rechargeable lithium battery, the battery life is usually about five years, the battery is used for a long time, the voltage will drop, when it is not enough to ensure the data in the RAM, the program in the RAM will be lost. If the user does not have a backup program, it can be quite troublesome.
Generally, there is a battery voltage detection circuit inside the PLC, and when the voltage drops to a certain extent, the PLC will alarm and remind to replace the battery. The instruction manual of PLC provides the method of replacing the battery. Generally speaking, after the PLC is powered off, because the PLC RAM power terminal is connected with a charging capacitor, even if the battery is removed, the charging power on the capacitor is enough to maintain the data in the RAM for a period of time, so if the battery is removed in a short period of time (usually 5 minutes) and then the new battery is replaced, the data will not be lost.
However, the user's actual use of the PLC environment is not the same, such as the capacity of the capacitor decreased, RAM power supply loop
Dust, sludge, etc. form a discharge circuit, which will speed up the discharge speed of the capacitor after the PLC power failure, so that the time is not easy to grasp. If the battery is replaced when it is live, the procedure is safe. Because the power supply will always
There is voltage applied to the power pin of the RAM chip. Of course, it is also necessary to be careful when replacing, pay attention to the polarity of the battery and avoid short circuit.
It is best to power on the PLC for 15 minutes (to charge the internal capacitor), power off, replace the new battery within 5 minutes, and then power on for a try.