On the way back from Beaverbrook, my TomTom kept shutting down, low battery, even though it was plugged into power from the car. No big deal, once I was on the M25, I can find my way home.
Even rechargeable batteries have a limited life. My TomTom XXL battery seems to have almost no life left, so I had a rummage round the internet.
I can take the device apart by peeling off the label at the bottom and removing two screws. Then it prises apart, and the battery can be replaced. The battery costs £4.99 on eBay.
I also updated the mapping, via the TomTom web site.