On most Jaguars the battery is in the boot, beneath the floor or behind a side panel, with jump-start posts under the bonnet. The cars use AGM batteries, and many with stop-start add a second, smaller battery that keeps the electronics steady during restarts. When either one weakens, a Jaguar tends to announce it on the dashboard before the starter does: a low battery message, stop-start unavailable, or a run of unrelated warnings that vanish once voltage is restored.
A Jaguar counts every amp in and out of its battery through a monitoring module on the negative terminal. After a new battery is fitted, that system has to be reset with a diagnostic tool, or the car keeps limiting features as if the old battery were still there. Jump leads and chargers should go on the body earth point, not straight on the battery's negative post, so the monitor sees the charge. A memory saver protects the settings throughout.