The auxiliary battery on the R172 is located behind the driver's seat.
What you will need
- Open the driver's door, then use the seat switch to move the driver seat forward and tilt the back reset forward.
- Ensure the ignition is turned off if the vehicle is equipped with Start/Stop store the key away from the vehicle.
- Remove the luggage net located behind the driver's seat. It is held in place with four clips. Just need to push the metal frame to release it from the clips.
- Next, you need to lift up the rectangular-shaped carpet. This will expose the access cover for the auxiliary battery behind it.
- Remove the two nuts on each end of the bracket.
- Remove the bracket to expose the auxiliary battery.
- Disconnect the negative terminal using a 10mm socket.
- Disconnect the positive terminal using a 10mm socket.
- Use electric tape to insulate the positive terminal. This will prevent any short between positive and frame.
- Disconnect the vent hose on the side of the auxiliary battery.
- Remove the auxiliary battery by pulling it forward.
- Install the new battery.
- Connect the vent hose. If the replacement battery is AGM, it won't have a vent connection. This is ok.
- Connect the positive terminal first.
- Connect the negative terminal last.
- Reinstall the battery cover, lower the carpet cover, and install the cargo net.