Your unit is made by Shimadzu. It just has the Fuji name placed on the cover. It is actaully a Shimadzu Mobile DaRt Evolution (aka MUX-200D). The CPU battery is a common button battery, CR2450. It can be replaced by removing the right side cover (The right side as seen from the driving position). You can see the battery easily once the cover is removed. DO NOT REMOVE THE BATTERY WITH THE KEY SWITCH TURNED OFF! You will loose the information stored in memory unless you make sure the key switch is turned ON before you remove the old battery.
The Emergency Brake release batteries are common 9 volt batteries. There are two of them, and they are located below the detector bin on the rear of the unit. You need to remove the detector bin to access the batteries, which are located beind a panel. The panel is opened by removing 2 allen screws located near the rear wheels on the underside of the unit.
The main batteries are much more involved than what can be written here. It will take between 2 and 4 hours to replace them depending on how fast you work and if you have another person to help. They should not be replaced until the users complain that the unit is not holding a charge. They generally last 18 to 36 months before needing replaced. There are 20 main batteries all together. They are a common battery found in many devices. Many manufacturers make this battery. Here's a link to one made by PowerSonic: https://www.amazon.com/Powersonic-PS-1270F2-Battery-Fast-Connector/dp/B006M4603O They are 12 volt, 7.0 AHr. PowerSonic's model number is PS-1270 F2. The "F2" in the model number denotes the terminal type. Make sure you get the PS-1270 F2, not PS-1270 F1. Shimadzu's part number for a set of 20 batteries is 503-68626. I don't know if this is also Fuji's part number. You will pay much more for the batteries when buying from either Fuji or Shimadzu.
Once any of these batteries are replaced, you will ned to get into the generator service menu to reset the date of replacement, otherwise you will continue to see the error messages, U01, U02, and U03. This is also too involved to expalin here. It may be best to call in vendor service and work with them to see how these things are done. Then next time you can do it yourself.
Hope this helps,