I went on a camping trip this week in a borrowed car. More room! Well I took my usb adaptor for the cigarette lighter slot and usb cable to charge to phone while away. But the adaptor didn't work! although 2 sat navs and the lighter all did so I was juiced up. no need to check the fuse. My phone was going to run dry on the first day so I was thinking what I could do. I had forgot to bring my 3 pin 240 v charger. I wonder if I could tear open a cable and try to connect it to the terminals in the socket. But messy and tricky idea. I then thought of the car battery as it was 12 v and I didn't need a voltage conversion. Then realised the car had jump leads in the boot. So I thought perfect. The only thing was guess which way yo connect it. So I guessed. it would only be the cheap adaptor that got fried. I connected the positive terminal to the centre pin of the adaptor and car body to the side prongs. Hey presto the adaptors light lit and could then plug phone in as normal and it charged Note I rested it all on the leads plastic bag as the grass may have been a bit damp and as the lead's clamps were close together on the adaptor. I also assumed the battery would have far more juice stored than the phone would require so as to not be able to start the car afterwards! Would I have been right that the terminals would be reversed while the car is running so its charged? As I was unsure of this I didn't run the engine while charging. Kept things simple which worked. Although the adaptor got a little warm so kept it in the shade not in direct sun to help keep cool as possible. Nothing to do with a Copen but thought I'd air it.
Yes and no. You were right, the centre pin is the positive connection - but you already now this now. No, the battery voltage does not reverse when charging. The alternator will produce a higher voltage than the battery (about 14.2v) and effectively force current back into the battery. So it would have not mattered if you started the car Rex.
