Technical 6v charging tech (phone, etc)

From what I read from your original post it sounds like you have the center post going to the negative (-) and the outer casing going to the positive (+). If this is so you have the polarity switch. You need the positive (+) going to the center post and the negative (-) to to the outer metal casing to the two outer contacts on your charger are grounded properly. I think the problem is the charger may be putting out 5 volts but the wrong polarity and your phone is not accepting it, it most likely is a safety feature on your phone that won't allow it to accept a switched polarity incoming power.

 

Correct. I switched it as you suggest and got SMOKE and burnt up one charger. I am not sure why.
Of course that was a quick mock up without a fuse to test the theory. But yeah, it was a no go. No smoke or anything until the little charger got plugged into the port so maybe it is a difference in chargers??? Are you now using this setup with other, newer chargers?

 

If you can find out what your chargers capabilities are then you will be able to determine what you will need to do.
Some chargers are 'smart' and can take a wide range of voltage/polarity input and still maintain the desired output.
Others are 'dumb' and will not maintain desired voltage, only a proportional voltage of input.

Stumbled across this, https://www.ebay.com/itm/DC-DC-Buck...-CAR-USB-Charger-PCB-Module-DIY-/221778815214

 

Yes, I was driving around this weekend charging my new phone I got last week. All seemed to be working. I was using a charger I bought a while back but I don't see why the new ones would be any different. The charger I'm using isn't the brand

 

you'll notice the one in Mike's pic above has a reverse polarity protection diode on the input...the one that you had that smoked, probably did not!