I've got one of the above, I won it in a Volvo promotion a couple of years ago and also had a mounting bracket and charging cable hard wired into my wife's XC70. At the time lifetime maps weren't free so I invested £90 I think it was to get them, now they do them free.
I've had a problem with the battery insofar it doesn't hold it's charge, or I should say it doesn't charge at all. Even after an overnighter on the mains charger I get a low battery warning the second I unplug it. Garmin were very helpful and told me the unit is useless as they don't do replacement batteries for it.
I Googled my requirements and found on Amazon several companies that do replacement batteries and also a little tool kit to remove the tiny torx #2 screws and lever off the back of the casing without damage. I ordered both on Thursday for £7.63 and a little package turned up today.
There's a video on You Tube showing how to do the job and I set to, all fingers and thumbs to do it, all I needed extra was a little bit of double sided adhesive tape to hold the battery insitu within the case. Once I'd got the back off the case it was only a matter of disconnecting two electrical plugs, prising the battery out of the casing and reversing what I'd done. It fired up OK before I put the two halves of the casing back together and I put it on charge for a couple of hours as recommended.
I've been playing about with it this afternoon and it seems to be holding it's charge well.
From what I can gather from t'internet battery problems seem common with Garmin, so if anyone has one with a battery fault there is a cheap and simple cure.