After crossing the bridge to try and enter Union city in Beyond a Steel Sky, you are blocked at the gate by not having access to a vehicle. You need to power Wendell’s truck, but his old power cell is broken. You need to get the one inside the 4YR robot that you meet after you cross the bridge. You can find it moving back and forth across the platform.
To steal the power cell inside the 4YR, you need to use your hacked MINOS device while standing between the conveyor belt and the vent. Make sure you can access both electronics simultaneously, which you can see when your MINOS says it detects two items you can interact with nearby. Once you have both of them, use your MINOS hacker to move the ‘Rapidly’ data block from the exhaust vent to the conveyor belt’s speed logic. Apply the setting once you’re done.
All you need to do is wait for 4YR to notice there’s a problem with the conveyor belt and walk over to it. There will be a quick animation of it being lifted by the magnet after standing on the pressure plate, and then you can take the battery over to Wendell’s truck. Make sure to speak to Wendell when you want to leave and enter Union City.