If the battery voltage is low, the ram data can corrupt, this can cause lockups. (True in almost any bat backup system.) As an overview, the battery feeds into a capacitor which then feeds the ram backup
circuit. The purpose of the cap is to keep memory alive while the battery is changed. If the system is working correctly, you can change the battery. The cap should do its job and keep the memory alive. (Unless the cap is too old.) You can reset the ram by discharging the cap, or by letting it run down. (1 to 24 hours without battery.) or, as mentioned, discharge it with a resistor. The only problem would be if the battery is soldered in. (use to run into this with keyboards all the time.) If not, no problem. While you are in there, look around and make sure the battery has not leaked and damaged things. Sometimes, the big old caps leak as well and that can be big trouble. If you find leakage, or are uncomfortable changing the battery, please take it to a service center. Good luck!