Hello, my problem is that I cannot replace the internal battery in the PanelView Plus 600 panel (year of production 2013). How is the old battery installed? How can I professionally perform this replacement? What other lithium battery can I use instead of the original one? The panel's fault is that it is impossible to permanently save any application to the internal memory. Turning off the panel's power supply causes the loaded application to disappear. Thank you in advance for your useful answers.