How to goose your leisure batteries – Reverse Polarity

Friday 2nd December 2015


We’ve had a problem with our leisure batteries for the last few weeks – whenever we switch the Sargent PSU charger off, within about 30 seconds the Sargent PSU display over the habitation door reports ‘ Leisure Battery – dangerously low’.

How could this be?

I had bought two new Varta 110Ah leisure batteries in June or July 2014 – they were now only 6 or 7 months old, they were fed by solar power as well as the Sargent PSU Charger and had performed faultlessly – until now.

Initially my thinking was that the readout may be wrong; possibly due to those nasty Portuguese road surfaces.

I also read somewhere that other MoHo’ers have reported a similar fault that was eventually found to be a poor/’gunged-up’ connection where the feed goes into the back of the main Sargent PSU ‘box’.

What should have been key to me was that the Fox regulator for the solar input also reported that the batteries were below an acceptable level.

Could it be that the guy that installed the solar system had taken a feed for the Fox regulator reading from the Sargent PSU feed? That would explain the Fox reading being the same as the Sargent reading.

Before I messed around with fuses and connections inside Twernt and the Sargent PSU box, I thought that it might be prudent to check out the batteries – they can’t be goosed, they’re new!!!

I isolated both batteries and got a multimeter readout of 12.1v and 12.4v – should have done a load test while I had them isolated (precautions were EHU lead removed and 12v system in the ‘off’ position).

We then spent a good few hours examining events and locations from a 12v Leisure Battery point of view to no avail.

In any event, the loss of the Leisure Batteries wasn’t affecting us whilst on EHU as the Sargent charger was able to maintain them sufficiently to run all 12v needs, and our needs were being more than met by the quality and surroundings of a luxury villa!

On a return to Camping Playa Granada, as a form of load test, I set Twernt to 12v only mode and I then noted that the water pump droned to a halt very quickly and that 12v lights quickly faded – that will do on the load test – dem der batteries were kafuggered.

Unless I could identify why they were ‘no more’, I wasn’t happy to replace them as the same thing could well happen to any replacement(s).

Back to thinking our way through Leisure Battery history.

All was well at Portimao where we didn’t have any EHU and we therefore relied on the Leisure Batteries, from there we went to Albufeira where we had EHU.

After Albufeira we went to Cabanas de Tavira – Camping Ria Formosa – and then I ‘twigged’ it.

At Camping Ria Formosa the staff visit your pitch to ‘lock-in’ your EHU lead to the supply post. You have to ask them to visit your pitch and remove your lead on the day that you leave the site.

When we arrived the site geezer ‘locked’ our EHU cable into the supply and Amanda confirmed that we had ‘juice’ in Twernt.

I remained outside ensuring that the EHU cable was laid in ‘rows’ as I had read that keeping a EHU lead ‘curled’ up either on the ground or on a reel has led to quite a few MoHo fires in the past – it is not good practice and therefore I faff around to make sure that the EHU lead is never touching another part of the lead at any point in the journey from Twernt connection to the EHU supply.

I did think that the examples of fires resulting from ‘curled-up’ EHU leads may have something to do with the quality of the EHU lead itself – are there any EHU leads that are mass-produced to a price in, say, China, and they have a thinner insulation/plastic coating than BSI standard EHU cables? – everyone looks to save a sheckle or two but it’s not worth it with some products!

About one week into our 4+week stay at Camping Ria Formosa it was noticed that the Reverse Polarity light was on at the Sargent PSU box.

In yet another forum topic that I had read in the lead-up to full-timing there had been a piece from an electrics expert stating that it is OK to be on Reverse Polarity insofar as appliances will still operate OK – just don’t mess with them by exposing wires and fiddling around, etc.

I therefore took the view that we would be OK (as we had been for one week or so) plus it would now be a hassle to call the site geezer back to re-connect the 2-pin Euro plug the other way round.


What the forum ‘expert’ had failed to mention and what I had failed to consider was the impact on the Leisure Batteries from the Sargent PSU Charger which, in essence, reverse the polarity over time in the batteries and render them pretty much useless.

That had to be what happened!!

I’m not sure what else was happening when the solar was supplying a charge to them through the Fox Regulator!!

It really doesn’t bear thinking about – it is possible for batteries to explode when subjected to this kind of treatment – we had been lucky (as had our pitch neighbours no doubt!).

I am no electrics expert but had trusted in what I had read from a forum expert – lesson.

Leisure Batteries are silly money in Spain – saw them @ €275 …..each!! – I had paid something like £220 for both (actual amount is in the ‘Set-up £’s’ page of this blog.

The decision was made to buy a decent sized car battery and operate with that until we get back to the UK.

I sourced one at the AlCampo Supermercado in Motril and chose the top one that they had – @ 91.5Ah – and paid €94.95 for it – fitted it to Twernt today and tested everything out in isolation and all 12v lights, etc. are working hunky-dory.

The goosed Varta batteries are staying with me as I’ve also read that, in some cases, it may be possible to take them to a battery centre where they have specialist chargers that can recover batteries from this type of cock-up.

I am also thinking that the Oxford Maximiser battery charger that I have may do a similar job – it is designed to restore lead-acid or gell batteries from an almost write-off position back to a usable state. Motorcycle intelligent trickle charge batteries are clever little things so this must be worth a try when we’re next on EHU – better still, let’s wait until we’re back in the UK and can then place the battery 50 yards away from anything an explosion could do damage to.

Should be fun.

I have recorded the above in the hope that it may trigger something for all other newbies to check for whenever they are on EHU.


An EHU post here at Camping Playa Granada – note that you have ‘pitch’ control to re-set the fuse box when tripped out (yes, yes, yes, 4 or 5 times since we’ve been here, floor heater, hob, hot water heater guarantee a trip-out!) – also note that the plug on many EHU bollards is ‘loose’ with internal wires exposed – we chose a ‘safe’ EHU bollard but children were playing on this site. ‘Elf n Safety where are you, come to think of it, I do know an Elf – Eric, job for you here!


A lot of these sites are either not regulated as they are in the UK or it may be that they don’t operate to the same standards as our CC and C&CC sites, etc.

‘EHU leads and they’re only £10’.

“I don’t believe it!”

“Margaret, you’ll never guess what’s gone and happened now!”

What was that TV programme where they said ‘Stay safe out there’?

Back to blogging the life shortly!!

16 thoughts on “How to goose your leisure batteries – Reverse Polarity

  1. Bad luck on this, I have used reverse polarity a few times in France with no issues with my batteries so not sure if this is the reason for your problems. Hope you don’t mind,I have just put a small post on Motorhome Fun, outlining what has happened to see if any of the electric experts can give any info. I shall drop you a line if there is any positive feedback. Loving your posts. Now we are into 2015 my calendar will be crossed of daily until April when we are off.
    Peter and Anna


    • That’s fine Peter, anything that gets to the root of this will be helpful, thanks. I’ve also had a PM from a trusted source saying that they too have done this many times. I cannot think of any other abnormality in using the 12V system except this reverse polarity, have now found some further info at supporting that reverse polarity can cause this problem. I did attempt to jump start the vehicle battery from the leisure batteries when we were at La Touquet but that was a long time back and the batteries were fine after that – apparently this is something else that can screw your leisure batteries up. Won’t apply during our return trip though as I bought a car battery to use on the hab 12V side. You may be off just after we get back so our roles could be reversed!


  2. There have already been a few replies one from a guy who is very up on electrics on MHs, He has said the reverse polarity would not cause your problem. If you can have a look at Motorhome Fun I have listed the post as Fried batteries


  3. Roy I remember when we were staying on Camping Ria Formosa (Feb/March 2010) our electrics were alright but opposite us some vans were connected with reverse polarity. I know that an English Motorhomer queried this with the management and was told that the problem would be rectified, clearly this hasn’t happened. I’am no electrician but I must admit don’t like the idea of RP (which sometimes you get on campsites abroad) and certainly didn’t realise that it could damage leisure batteries like this.


    • It seems to be causing some debate with some saying it can cause damage and others saying it can’t. All I know is that our new-ish batteries are toast and they were good before Ria Formosa and that the reverse polarity incident has been the only abnormality. With the Euro 2-pin plug it is easy to connect the wrong way round, I’ve done it a few times but instantly corrected it once Amanda called out that the red light was on at the Sargent ‘box’. We missed checking that at Ria Formosa and I think that was due to the site chap fitting the plug himself – he locked our EHU cable into the EHU post housing. After that, all seemed to be working OK anyway, I didn’t switch the PSU Charger off to test the batteries whilst there though. The support theory that reverse polarity can cause battery goosing is at


  4. Interesting Roy, but a bugger waste of dough if you can’t get the Varta’s back to life. As an ex. Tyre and Battery man l have, in the past, rectified similar problems by draining all the electrolyte out which in effect cuts the contact between the positive and negative plates that reside in each of the 6 cells, then refilled it with 1260 battery acid. Stand for 24 hours then put a steady charge to it until 12.4v is achieved. Worth a try if you can access the acid. Good luck.


  5. Also a good idea to paint a red blob on the positive pin of your 2 pin Euro plug so once you’ve “dibbed” the supply to establish which connection is the positive, you can plug in accordingly.


  6. I have fitted a reverse polarity change over switch in every caravan or motorhome we ever had , as we were caught out before , and also carry reverse polarity short leads already made up . also carry a 13 amp test plug , which is all ways left in a socket


    • Hi David, we do have a 13 amp test plug but tend to rely on the red light appearing on the Sargent PSU box – this indicates reverse polarity – just missed doing it at Ria Formosa but NEVER again!!


  7. Oh dear what have you done
    You will need to go to b&q and pick up a mains plug tester to check to test for polarity. A lot of people normally make up a spare connector with the live and neutral reversed and then mark it as revered polarity .
    You no doubt have one but i binned my consumer unit to buy a double pole unit instead.
    I would have thought that your charger would have tripped a fuse,if so you wouldnt be getting any charge into your batteries.What do i know though hee hee
    Always though when you hook up your electric cable before you do anything it is good practise to press the button on the rcd to make sure that it trips.If it does great but if it doesnt dont use it.
    Take care folks
    The coolas


    • Hi Coola, is your house up for sale? How’s it going? You’re on the last leg before becoming a full-timer!! Whoops, sorry, electrical stuff…..I do have a 13 amp tester but use the Sargent PSU red light that indicates the same deal. If the PSU charger had tripped a fuse then the batteries would still be OK? We’ve been on EHU since before Ria Formosa, also when I put the new ‘car’ battery in tother day, the PSU took the charge from 12.5V as bought to 13.2V with the charger on and 12.8V when I switched the charger off to check it before we left to return to the villa, so the charger must be working fine. Good point on the RCD, caution is the order of the day on Euro campsites.


  8. That’s horrible news, thanks for posting that for all to read. It’s something that we are aware of but how do you know if it’s reverse polarity? That’s an outdoor job for Mr Always Right to check on, however as a woman that’s something for me to worry about and of course that will lead to being accused of “nagging” whenever we arrive at a new site.

    Take care and keep blogging.


    • Haha, poor Iain! Saw a picture of a battery exploding and it’s not a pretty sight so awareness of this is a good thing.

      Final blog about to be published before we head north on Wednesday (spending 2 nights ‘wilding’ down here – ‘just in case’ on the battery front!)

      Hope we get to see you both soon!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s