Yes, it is an internal battery backed up RAM: http://pdf1.alldatasheet.com/datasheet-pdf/view/23329/STMICROELECTRONICS/MK48Z02.html

Data Sheet says worst case is 11 year battery life. The Z version (Zero Ram) last much longer than the T version (real time clock with ram). I am guessing your 4802 is a very early version. It would be interesting to see the date code.

These parts, unlike some others, have their battery life determined by Date of Manufacture. Other devices actually have a shelf life circuit which keeps the battery disconnected until the unit is first used (accessed). In these devices, Date Code doesn't matter unless they have been used or tested on a RAM tester. Temperature can greatly effect battery life too. Higher temps, like that in a pinball head, can shorten the battery life.

So, since both are older games, it is possible you could be at the end of life for the batteries (50% expected to fail in 20 years).

Since your board are probably socketed already, you may want to consider the various NVRAM options that have been recently discussed here on Pinside. There are a number of sellers, all offering good products but at varying price points.

Of course, you could just wait until they fail. You may not own the game at that point any longer.