Is this down to the TomTom having one of these perishing Lio-ion
batteries?  I'm rapidly coming to the conclusion that they are almost more
trouble than they are worth. My iPAQ PDA refused to play at the new year,
even after a full hardware reset all it would do is make a quiet click
every 2 seconds. Tried all the things suggested on the web help pages and
even went into live chat with HP Support all to no avail(*). So I left it
clicking. Several hours later I noticed it had gone quiet, the thing had
restarted itself. Bunged it on charge, it locked up again a while later
but recovered when left clicking, fully cycled the battery and it's been
fine since. I reckon that the protection/charge circuitary in the battery
had got confused and would shut down as the PDA tried to power up.

(*) Well the result was send it back under warranty, this was on the 31st
Dec. Today, 3 weeks later, I get the email from HP that they have arranged
for UPS to collect it. Sent a message to them closing the fault and
telling 'em to cancel the UPS, several hours later I get and email from
UPS saying they are going to collect... Doesn't seem any point it'll only
be NFF and I'll be without my PDA for heaven knows how long.

Which vehicle?

I've used the clock feed for mine - it's about the only thing left with
permanent power these days.