Garmin i3 fuse problem = probably generic

[SandLake]

I have just blown the second fuse in my i3, last time I went to Halfords and after a lot of head scratching they sold me a replacement - now I'm not so sure.

So, I have 2 questions

1, What is the correct fuse?

2, Is there a correct method of attaching external power?

I have done some research on this and in both cases the fuse was blown in cars other than my own, so it could be a problem with the other cars, even as serious as the cigarette lighter socket having the incorrect polarity (doesn't mean much to me but sounds serious) but I'm just wondering if there is anything lse I need to be aware of?

Thanks

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