I'm looking to by a replacement sat nav - the last one we had (Navigon) needed to be plugged in to the car's power point all the time, otherwise it ran out of battery within half an hour or so.
Is this normal, or should I expect to be able to charge it and then run it on the battery for a few hours?
All rechargeable batteries will eventually wear out and fail to hold charge.
You will probably find that the cheapest sat navs have the cheapest batteries in them, so it is probably worth buying one of the major brands such as Garmin or TomTom.
Thanks Marty - what I didn't explain very well is that it needed power even when it was new, and I wondered if that was common to all sat navs - i.e. are they power hungry, and none of them last long just on battery, or was it just a problem with mine?
They are pretty power hungry though, when new my TomTom 720 only got about 2 hrs before running out of juice, big colour screens are notorious juice users.