Our C4 UrS-cars have the battery located under the rear seat. To access the battery, you need to remove the rear seat by removing the two large black Phillips (+) head machine screws. Lift up the seat (disconnecting the seat heater connectors, if you have them) and you will see something like this (except without the tools in the footwell):



The above was taken during the fuel pump relay DIY and the battery is missing the Positive (+) terminal cover (Item 4 below). That cover is normally there - just off during the relay install. The piece of tape on the battery has the radio code on it (which you need after you disconnect the battery). C4 UrS-car fires have resulted from the rear seat frame grounding on the (+) terminal.



A variety of brands make batteries for our cars, e.g. OE Autobahn, Sears Die Hard,Autozone Duralat, WallyMart, Johnson Controls, Allstate, etc. The battery *should* be a Type 41. A couple of things are important:

1) height not higher than about 6 5/8" otherwise the terminals are more likely to hit the bottom of the seat and/or the Item 3 (above) hold down clamp won't be long enough.

2)the battery has to have a vent to which you can attach the OE vent hose (Item 5 above)(or equivalent), which is directed through the Item 7 grommet to the outside (underneath) the car. Not running this vent hose = acidic fumes and hydrogen gas in the inside of the car. Not a good idea.

Jumping the battery is a bit risky. There have been damaged ECU's as a result. Jumping, if you have to, and trickle charging can be done from the engine bay, without even seeing the battery: There is a ground (-)post beside the right hand side strut tower and there is a positive (+) under a black plastic cover on the engine bay cowl. If you don't have a (-) ground post by the strut tower, ground the cable to the engine lift lug or one of the strut tower bolts.