Reverse polarity light on. Can I still use charger safely?

[RV-AL]

i am in Spain at the moment, having left my reverse polarity cable in UK! Every site I have stopped at ehu works fine until I switch on inbuilt charger when the reverse polarity sign comes on, so I switch it off again. On a couple of sites they have standard eu socket so I just turn it upside down and all ok. Current site has type 2 connector so can’t do that. It it safe for me to ignore the warning light and charge anyway?

The van is a 2018 auto-trail.

 

[Lenny HB]

On the other hand , DC voltage does have polarity , + positive and - negative , current always flows from positive to negative... so it can be connected reversed.. as you describe when connecting the leads of a charger to a battery

Just to be pedantic it actually flows from negative to positive.

 

[wiff2110]

Never had any real problems using reversed polarity EHU while touring France and Spain decades ago but I think I remembered about 1/4 were reversed. I did make a patch cable with a crossover to connect in line with the EHU hookup though - belt and braces.

I carry a cable with reverse connection + and - it’s only about 12 inches long and I connect it between the EHU and my motorhome when needed.

 

[David and Sally]

Just to be pedantic it actually flows from negative to positive.

To be even more pedantic, the actual electrons flow from negative to positive poles. The current does flow positive to negative however. Can’t get my head around that one.

As the direct current flows, the electrons, which constitute the electric charge, flow from the point of low potential to the point of high potential. They move from the negative terminal to the positive terminal and the resulting current is in the opposite direction (from positive to negative).

 

[TheBig1]

Very simplified explanation. AC mains flows in a sine wave, starting at 0volts (in this exp) and increasing to 120v, then falling past zero to minus 120v, before returning to zero and repeating at 50 cycles per second. This gives you the so called Alternating Current used in mains connections. So both wires have a high voltage relative to each other.

Now the complicated bit. In SOME not all supply networks, back at the sub station, the Neutral can be attached to the Earth, but not the Line (Live). So it is or was normal to put a switch only in the Live wire supplying an appliance. Often you see double pole switching in high current devices to switch both.

Does any of this make reversed polarity dangerous? NO, not unless there is a fault in the appliance to Earth and the trip at your motorhome mains distribution is also faulty. Remember that not all foreign bollards are Earthed so there may be no connection to Earth in your Motorhome when plugged in. Nobody without the relevant qualifications would open an appliance or work on the supply cables whilst plugged in

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[Bodoge]

And to add to the mix, loop fire alarm systems have both ac and dc running along the same cable in opposite directions, I had difficulty getting my head around that one.

 

[bigtwin]

If you need to check amperage it has to be plugged in.

Under what circumstances do you anticipate needing to check the amperage by poking under the covers of an appliance?

Ian

 

[bigtwin]

Nobody without the relevant qualifications would open an appliance or work on the supply cables whilst plugged in

Indeed.

Ian

 

[Bodoge]

Under what circumstances do you anticipate needing to check the amperage by poking under the covers of an appliance?

Ian

Best laymans way is to use a plug adapter that analyses wattage etc being used.

 

[bigtwin]

Best laymans way is to use a plug adapter that analyses wattage etc being used.

I wasn’t looking for an answer about how to do it but rather why someone might use the need to measure current as a reason why ’reverse polarity’ might be dangerous.

Ian

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[Bodoge]

I wasn’t looking for an answer about how to do it but rather why someone might use the need to measure current as a reason why ’reverse polarity’ might be dangerous.

Ian

I wasnt necessarily answering but offering advice on a safer method. As you say, i cant see why, but some are dangerously inquisitive.

 

[scotjimland]

Just to be pedantic it actually flows from negative to positive.

what do you mean by "it" current or electrons ?

Current flows from positive to negative and electron flows from negative to positive.

In my post I was referring to CURRENT ... not electrons ..

as I said >>>>

DC voltage does have polarity , + positive and - negative , current always flows from positive to negative...

 

[scotjimland]

To be even more pedantic, the actual electrons flow from negative to positive poles. The current does flow positive to negative however.

you beat me to it.. didn't read your post before rebutting Lenny's pedantic post about my post ..

 

[TheBig1]

what do you mean by "it" current or electrons ?

Current flows from positive to negative and electron flows from negative to positive.

In my post I was referring to CURRENT ... not electrons ..

as I said >>>>

Don't get caught up in an argument about physics Jim, it goes over the head of most here. The reason I didn't add a current flow description in my answer.

For those not qualified, I will explain. Mains voltage will hurt you by making your muscles contract and kill you as high current passes through your body to Earth, stopping your heart. Funny thing electricity, used wrong will stop a beating heart, used right with a defibrillator can sometimes restart a stopped heart. Not something to be messed with if you are not suitably qualified

 

[OldCodger]

Thanks for all the responses. I get the reverse polarity generally not being a problem with 13 amp circuit. My concern is with the inbuilt charger. If I am in the UK and connect a standalone charger to the vehicle battery and absentmindedly connect life and neutral cables to the wrong poles of the battery the charger says polarity reversed and I disconnect the cables and connect the right way round. I was sort of assuming that it was the same effect with reverse polarity from EHU when using charger. Aren’t I effectively connecting +ve to -ve and Vice versa if I use the charger.

apologies if I am being thick!

It doesn’t matter which way round the 240v is connected. The charger will only ever put out 12v “the right way round”. Reversing the 240 will not reverse the 12v

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[Old Gibber]

The battery charger converts AC to DC and drops the voltage, this is done through a transformer and a full wave bridge rectifier so the outputs will not change, ie output positive will always be positive

Not these days generally. For many years now most battery chargers use switched mode power supplies.

 

[cyberyacht]

You're in Spain where the sky is blue( mostly). Why aren't you using solar panels anyway?

 

[Old Gibber]

Does make me wonder why Sterling or whoever went to the trouble of putting a reverse polarity light in if it makes no difference. I do know it doesn't matter if polarity is reversed, but why tell us

No idea. As the OP has an Auto Trail, it will be a Sargent unit. My current Sargent unit does not have such a warning light. We had a similar system in Norway and it always lit up, it appears the way their mains is wired up at the generating station is very different to everyone else's. Hey ho, I'm still alive.

 

[Speve]

I wonder where The LithiumConvert disappeared to?

 

[JustifiedAncient]

Very simplified explanation. AC mains flows in a sine wave, starting at 0volts (in this exp) and increasing to 120v, then falling past zero to minus 120v, before returning to zero and repeating at 50 cycles per second. This gives you the so called Alternating Current used in mains connections. So both wires have a high voltage relative to each other.

The AC voltage goes a lot higher than 120v!!
In the UK we have 240v RMS voltage (Root Mean Square) so the peak voltage is 240/0.71 = 338v approximately.

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[Raul]

Just to be pedantic it actually flows from negative to positive.

I would say depends on the source. If it’s a battery source, then I agree, but, only when discharging. When you charge, it’s exactly the opposite of discharging. If you have a clamp meter check this on charging, and discharging on positive cable, and you will se the amp value changes to minus when you charge. And when you clamp the meter 180 deg the other way, it changes again. Like CT clamp meters, have a directional arrow to indicate direction of travel.

 

[TheBig1]

The AC voltage goes a lot higher than 120v!!
In the UK we have 240v RMS voltage (Root Mean Square) so the peak voltage is 240/0.71 = 338v approximately.

INDEED IT DOES 120v up 120v down combined gives 240v. Despite quoting RMS average value the actual voltage read across the incoming mains my be higher or lower in different areas. I know a chap in the North East regularly sees 252v on his supply. And another on Bodmin Moor sees 215v. Quoting an average 240v helps people that don't know understand

 

[TheBig1]

I would say depends on the source. If it’s a battery source, then I agree, but, only when discharging. When you charge, it’s exactly the opposite of discharging. If you have a clamp meter check this on charging, and discharging on positive cable, and you will se the amp value changes to minus when you charge. And when you clamp the meter 180 deg the other way, it changes again. Like CT clamp meters, have a directional arrow to indicate direction of travel.

How to make things complicated for people lol Most on here....plug in, does it work? Yes, happy days, No, panic. No in between nor knowledge of the science behind the supply of electricity

 

[JustifiedAncient]

INDEED IT DOES 120v up 120v down combined gives 240v. Despite quoting RMS average value the actual voltage read across the incoming mains my be higher or lower in different areas. I know a chap in the North East regularly sees 252v on his supply. And another on Bodmin Moor sees 215v. Quoting an average 240v helps people that don't know understand

No, it goes up to +338v and down to -338v in a sine wave.

 

[greyowl989]

I carry a cable with reverse connection + and - it’s only about 12 inches long and I connect it between the EHU and my motorhome when needed.

Yep that’s what I made up years ago

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[Bodoge]

The original question seemed so simple, * can I * and yes we can make a mountain out of molehill but as usual, it's been laced with good advice and good humour, it's what Sundays are made for, fun funsters.

 

[RV-AL]

You're in Spain where the sky is blue( mostly). Why aren't you using solar panels anyway?

The sky is cloudless and I have used nothing but solar for two weeks but checking ehu on each site. Cloud and even rain next couple of days so may need to charge a little but hopefully not. We have 420 watts of solar and 209 ah of lithium so I don’t think I will need to panic. Just trying to be a good Boy Scout.

Thanks for all the advice. Some of which was miles over my head but appreciated anyway.

 

[Clive Mott]

Yes

 

[bigtwin]

Yes

Succinct, and to the point.

Ian

 

[Buzzbuzz]

Just turn your two pin plug upside down on the campsite electrics

Most on site camp sites sell male/female 3pin connectors. Open the male connector and reverse the +&- wires. Label the connector 'Reversed polarity'. Plug it into the site's supply.

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[Petroleumblownapart]

i am in Spain at the moment, having left my reverse polarity cable in UK! Every site I have stopped at ehu works fine until I switch on inbuilt charger when the reverse polarity sign comes on, so I switch it off again. On a couple of sites they have standard eu socket so I just turn it upside down and all ok. Current site has type 2 connector so can’t do that. It it safe for me to ignore the warning light and charge anyway?

The van is a 2018 auto-trail.

Polarity of AC current is irrelevant to any AC device. Reversing polarity takes place when on AC at least 50 times every second (ALTERNATING) in any case!
The polarity of the lead or EHU only affects the safety aspects of anything without double pole isolation if you are fiddling with EHU power connected, which is not for the untrained uninformed or unprepared human.
Not sure about PME supply wiring though..... Any qualified electricians on the forum would know though....?