There is a battery on the Motherboard. Coin cell style 2032. These will die and when they do the game won’t boot.
Don’t confuse this with the security key that kinda looks like a battery but is on a satellite board.
These motherboard batteries will take you well over an hour to get to. Lots of stuff has to come off. You will also have to know how to restart an older motherboard with the power on jumper and reset the bios settings once running.
Not aware of an ION unlocked hard drive. Some for older Megatouch machibes. You can only get up to 2014 software for your machine. So almost the newest.

If the game is running I would not mess with the battery. Just know that one day you will turn the machine on and it will not boot. This will either be from the battery being dead, or the entire motherboard being dead.

Some of the older Megatouch machibes will semi boot and give you an error that tells you to hit F1 on a keyboard. The Auroras will not do this. Just a blank screen telling you no signal input.

The non recommended way to “jumpstart” the motherboard is to short the green power supply wire with any ground. If done incorrectly you will toast your motherboard and can not be fixed after that. You really need to start these by jumpering the pins that would normally be hard wired to a PC on off switch. That is not on the Megatouch machibes

When the motherboard goes sometimes you can recap them to get more life. If you recap and it doesn’t fix you pull the DBA and throw the rest away.