12v Cigarette socket is blowing my phone charger(s) - why ?

[Steve Clayton]

[ QUOTE ]
I think it's because of the water analogy that is often used to explain electrical circuits. It's a pretty good analogy for most purposes but it does give the impression of electrons piling up at the end of the positive wire trying to get out!

In fact the electrons are flowing the other way, and anyway it is just not like that. A current will only flow given a potential difference and a conductor. The terms pos and neg are just conventions and could have been reversed. And they only have meaning relative to each other. So a neg potential is positive with respect to a more neg potential.

Has that helped or muddied the waters even more?!

[/ QUOTE ]
Don't get me started on what is faster - hole flow or electron flow? /forums/images/graemlins/laugh.gif

 

[VicS]

This is presumably the one

HERE

Available from other chandlers as well

 

[pandos]

I did similar damage a few years ago, there was a safety diode in the system that when the power was put in the wrong direction it blew and became a pure short which in turn blew the fuse.

The short term cure was to cut the diode and replace the fuse.

 

[Captain Mortsik]

I wired up a cigarette socket to my batteries (battery to small bus-bar + and -, busbar positive to switch, switch positive to cigarette socket , and cigarette socket back to bus-bar negative terminal).
...

I noticed I had connected the +/- terminal at the back of the Cigarette socket incorrectly (wrong way around, the markings on the socket were extremely hard to see) - so I switched them, charger still didnt work. I tried a second car phone charger - it worked ok ! Puzzled, I reversed the polarity and tried again - the second charger now didnt work, and continued to not work when I corrected the +/- to the right terminals.
...

Hey there,

The same happened to me! I blew two usb inserters/chargers. The thing is that I did pay attention to the right polarity but what are the chances!!! The previous owner had plugged in the cable (black and red!!!) the other way around ?‍

I would never expect that that is why I kept trying and burning the chargers. This morning I changed them and it all worked.
My God though, the moment I was connecting black and red together I was afraid I would burn the boat down ???

 

[Alfie168]

Thanks Steve, that clears it up for me. I realise putting the fuse on the negative side will protect the circuit itself (after blowing the device on the circuit).... while putting the fuse on the positive side protects the device as well. Although I've always followed the instructions for positive/negative connection on electronics such as VHF / GPS etc., I didn't fully realise the significance of the sensitivity to polarity for some devices connected to the cigarette lighter socket - Now I'm happy that that was the problem.

ps. While the phone charger is obviously damaged because of it's sensitivity to the polarity, is it likely that it (or any other polarity-sensitive device) could have caught fire ?

Its certainly possible as with thin cables the ampage can be high and you get heat and things melting.......and........fire. If there is no safety mechanism (fuses) the whole thing can stack up the wrong way quite quickly.

 

[Old Harry]

a 12 year old thread

 

[Alfie168]

a 12 year old thread

Not even close to the 19 year old VHF thread then........come on...records are there to be broken....

 

[Captain Mortsik]

a 12 year old thread

Luckily electricity is still in use hahahaha
(silly me, I gave re-birth to that thread

 

[Momac]

The concept of only fusing the positive connection is perhaps a carry over from motor vehicles where the negative is always connected via the metal body.

Usually negative earth.
However some very old cars used to be positive earth.

 

[Paulg25]

Usually negative earth.
However some very old cars used to be positive earth.

Think that was shortly after the horse!!

 

[RichardS]

Think that was shortly after the horse!!

I don't think so. My Dad's cars in the 1960's and perhaps even into the 70's were positive earth. By then, apart from the local rag and bone man, there was not a horse to be seen in the city.

Richard

 

[JumbleDuck]

I noticed I had connected the +/- terminal at the back of the Cigarette socket incorrectly (wrong way around, the markings on the socket were extremely hard to see) - so I switched them, charger still didnt work. I tried a second car phone charger - it worked ok ! Puzzled, I reversed the polarity and tried again - the second charger now didnt work, and continued to not work when I corrected the +/- to the right terminals.

Just as a matter of interest, why did you decide to try the wrong polarity again? You already had one charger which didn't work after being connect the wrong way round ...

 

[JumbleDuck]

I don't think so. My Dad's cars in the 1960's and perhaps even into the 70's were positive earth. By then, apart from the local rag and bone man, there was not a horse to be seen in the city.

I had a 1966 Herald with positive earth.

 

[oldmanofthehills]

You think thats bad, Western Region EK10,000 signalling circuits have fuse in wrong leg. No end of fun and games when mixed up with more modern NR style circuits with fuse in the B50, or worse still existing circuits modified by those unaware of the WR style

 

[Captain Mortsik]

Just as a matter of interest, why did you decide to try the wrong polarity again? You already had one charger which didn't work after being connect the wrong way round ...

Well, as it has been 12 years since, I am sure he will not remember ???

 

[PaulRainbow]

 

[JumbleDuck]

Well, as it has been 12 years since, I am sure he will not remember ???

Oops.

 

[Captain Mortsik]

Oops.

Don’t worry, it was all my mistake reviving that thread in the first place ???
It helped me solve my issue though, so, its resurrection was all worth it?

 

[penberth3]

a 12 year old thread

Everybody should now have a multimeter that tells them which is Pos and Neg.

 

[Rappey]

If you Google a technical boat query that may not be a common item ybw threads can often come up. You click on it and you may then read from beginning, then post. It's so easy to not look at the date. Now it can show up as a new post for us users, we join in and don't look at the date.
I came here as i couldn't believe how many post there were to something that didn't look that complex - and didn't look at the date ?
On the plus side it's great not to be seeing brexit or corona and some may learn why penberth suggests we should have multimeters ?