Mick.B - have a look here:
Garmin gpsmap 295 will not run from internal battery power - FixYa
You should also be aware the Varia MC621 lithium internal clock battery in the 296 is absolutely tiny, like what would you would find in a ladies watch. If it takes a long time to acquire satellites and the time is not correct, it need either replacement at Garmin for about $300 or you DIY for about $10.
