caravan leasure battery charging

[harryh31]

Hi.
I have two leasure batteries in my caravan.
Each one has to be charged up seperatly from the connections within the battery compartment.
One battery is in the battery compartment, the second battery is adjacent to the wheel arch on the opposite side of the caravan.
Is it possible to connect the batteries in some way , that I dont have to swop the batteries over physically when one of them runs down.
The batteries are normally charged seperately from either .....mains supply.....car alternator....or 40 watt solar panel fixed onto the roof of the caravan and I have to physically swop the batteries over when they need charging.
harryh31

 

[ProfJohnL]

Hi.
I have two leasure batteries in my caravan.
Each one has to be charged up seperatly from the connections within the battery compartment.
One battery is in the battery compartment, the second battery is adjacent to the wheel arch on the opposite side of the caravan.
Is it possible to connect the batteries in some way , that I dont have to swop the batteries over physically when one of them runs down.
The batteries are normally charged seperately from either .....mains supply.....car alternator....or 40 watt solar panel fixed onto the roof of the caravan and I have to physically swop the batteries over when they need charging.
harryh31

I don't like the sound of this system from a safety point of view. The battery in the proper enclosures should be fine, but batteries can give of fumes so they must be properly secured in a box with external ventilation.

To over come your original question, provided both batteries are the same size (Ahr) and condition, then by using large gauge wires you could link both batteries in parallel (+ to + and - to -). Doing this both batteries will charge at the same time, and will both power the caravan concurrently.

 

[MoisesZer]

Hi.
I have two leasure batteries in my caravan.
Each one has to be charged up seperatly from the connections within the battery compartment.
One battery is in the battery compartment, the second battery is adjacent to the wheel arch on the opposite side of the caravan.
Is it possible to connect the batteries in some way , that I dont have to swop the batteries over physically when one of them runs down.
The batteries are normally charged seperately from either .....mains supply.....car alternator....or 40 watt solar panels fixed onto the roof of the caravan and I have to physically swop the batteries over when they need charging.
harryh31

it sounds very effective but I think it is hard to implement as you need to swap the batteries..

 

[bertieboy1]

Prof,
I don't know what your caravan battery box is like but mine's is totally enclosed and doesn't have any ventilation.

 

[starlightdj]

Hi, no visible ventilation holes but what about the gaps where the external electric wires and aerial leads enter at the bottom of the door. any smells or vapours can escape through these gaps

The wires from the battery to the inside the van pass through rubber grommets to prevent vapours entering the van.
Cheers
John

 

[Oldsalt49]

Hi, no visible ventilation holes but what about the gaps where the external electric wires and aerial leads enter at the bottom of the door. any smells or vapours can escape through these gaps

The wires from the battery to the inside the van pass through rubber grommets to prevent vapours entering the van.
Cheers
John

John,
My battery box has a seal on the division between the battery and electric hook-up compartments. I think the battery compartment ventilates at the bottom, although hydrogen being lighter than air, will accumulate at the top of the compartment. I'm guessing there must be ventilation at the top somehow?

David

 

[xtrailman]

This question of ventilation has never really been answered on any forum I've been on.

In theory the ventilation should be at the top, but no one is certain there is any in the standard box.

what I am sure of is the box isn't usually sealed, if you look carefully often where the cables enter the caravan there is usually a loose fit, especially if a mover has been fitted.

Technically a battery inside a caravan should be a GEL type.

Interestingly Bailey now fit the Unicorn V3 battery below floor level, effectively inside the caravan below an access cover.

 

[colin-yorkshire]

This question of ventilation has never really been answered on any forum I've been on.

In theory the ventilation should be at the top, but no one is certain there is any in the standard box.

OH, really. I would have thought it had many times . no part of a caravan is air tight it is hard enough to get them water tight [apparently] so ventilation should not be a problem not even in the battery box. and then there is the charging issue,
a standard EHU will only fill the battery to 80% @13.8v and a solar panel would only trickle charge it, so gassing should not occur even if left perminantly connected,
plus many batteries are now sealed for life. I really cannot see why some see problems when there is none.
does anyone really believe that manufacturers are unaware of a problem if one existed,

 

[Raywood]

In theory the battery box should be sealed of to prevent dangerous fumes entering the caravan. I do remember our old Trophy simple had the battery in the bed locker with no cover and we never had a problem nor have I heard of any one having problems so not sure how dangerous it is.
My niece did make her own motorhome up though and lived in it for very long periods. That had the battery in the bottom of the wardrobe and she did have problems with holes appearing in clothes so it may need more exposure than just short holidays for the problem to show up.
Given the low weight allowance on many caravans a second battery could cause problems there.

 

[ProfJohnL]

Now lets get this issue of battery ventilation sorted.

All lead acid batteries when they are charged have the potential to give of fumes. The fumes are Hydrogen and Oxygen, which in the proportions that are produced have the potential to burn very vigorously, and if enough has been produced and retained in a confined space it can explode.

The chances of a battery out gassing any substantive quantity in this way essentially depends on the charge voltage. But even at the 13.8 V typically used in caravans some gas can be produced.

Hydrogen is lighter than air so it will try to rise. So if a battery is contained within a caravan the gasses will rise into the living space, where there an be sources of ignition.

This is why batteries should be properly contained in ventilated containers. The container should also be inert to battery acid (H2SO4)

Some battery manufacturers fit their batteries with a ventilation tube. This should be tracked to the outside. The tube will vent gasses and any excess acid that might escape from the battery.

Historically when batteries were first fitted to caravans, they were often just clamped under a bed. But it only took a few instances of fires or acid spillage for a proper containment solution to become recommended.

 

[FrenchChuffed]

I fitted 2 x 110a batteries to my previous caravan. the additional battery was in an identical battery box fitted the opposite side of the van. I had some 60a cable joining them (a bit ott) but I also used a battery to battery charger from the towing vehicle to charge them instead of through the standard13 pin wiring. worked very well could off grid for quite a time, especially when touring in France with there silly low ampage connections not required.

 

[Gozza]

Now lets get this issue of battery ventilation sorted.

Prof, I think the thing that most of us don't understand - or at least I don't - is the ventilation of a caravan battery box.

I'm prepared to accept that my battery box is sealed well enough to stop hydrogen leaking into the caravan - at the very least a close study of the inside of the box suggests that it was designed with that in mind. Having seen film footage of the Hindenberg disaster I also totally understand why that has to be.

What I don't get is where does the hydrogen go? My battery box appears to be well enough sealed around the flap that rainwater can't get in, so can gas still escape? The only penetration I can see in the seal is the small hole that the bottom that the EHU cable comes in through - and if hydrogen starts escaping through that then I have a battery box full of hydro/oxy mixture!

I'm not challenging anything about the need to keep battery gas out of the caravan, jut trying to work out exactly how the battery box is ventilated when it looks like an effectively sealed unit.

 

[FrenchChuffed]

Let’s face it, Lead acid Batteries only really ‘Gas’ when they are being rapidly charged, and the systems in place on caravans will never do that even with the supplied so called intelligent chargers. The trickle charge from the vehicle is minimal and from any solar panels will also be minimal.

So unless someone covers the roof of the van with solar panels or puts a serious 50a charger in place of the one supplied, gassing just isn’t going to happen. It’s a perceived problem, which is supposedly covered by a battery box that is sealed from the van interior and leaks air out of the bottom flap by the wire inlet.

 

[Royston]

I have a bailey senator. on a recent trip to Kent, we noticed a unusual smell coming from somewhere within the caravan, unable to source where the smell was coming from we finally located it was appearing to come from behind the fire ,which is located in front of the external battery box, going outside unlocking the battery box discovered that the battery was very hot, checking the battery volts only showing 10 volts despite being charged on unit charge .
Pulled the plug on the mains within 1/2 hour the horrific smell had gone, within the caravan, my question is if we could smell this odour within the van does that mean that the gasses given off were also present within the van, outside could not smell anything until I opened the battery box, Called a external fitter who confirmed that the battery had been cooking, ands we were lucky it had not exploded, supplied us with a brand new battery checked the internal charger .which had been working overtime to try and charge the battery, everything was okay.
The new battery came complete with a ventilation tube which was not long enough to reach the outside at present it is in the battery tray, but I am going to get a extension tube so that it exits alongside the electrical cable to the mains
That smell is something I will not forget in a Hurry.

 

[ProfJohnL]

Let’s face it, Lead acid Batteries only really ‘Gas’ when they are being rapidly charged, and the systems in place on caravans will never do that even with the supplied so called intelligent chargers. The trickle charge from the vehicle is minimal and from any solar panels will also be minimal.

So unless someone covers the roof of the van with solar panels or puts a serious 50a charger in place of the one supplied, gassing just isn’t going to happen. It’s a perceived problem, which is supposedly covered by a battery box that is sealed from the van interior and leaks air out of the bottom flap by the wire inlet.

See Roystons post.

 

[colin-yorkshire]

Let’s face it, Lead acid Batteries only really ‘Gas’ when they are being rapidly charged, and the systems in place on caravans will never do that even with the supplied so called intelligent chargers. The trickle charge from the vehicle is minimal and from any solar panels will also be minimal.

So unless someone covers the roof of the van with solar panels or puts a serious 50a charger in place of the one supplied, gassing just isn’t going to happen. It’s a perceived problem, which is supposedly covered by a battery box that is sealed from the van interior and leaks air out of the bottom flap by the wire inlet.

See Roystons post.

With respect to the Prof's post, the issue of battery ventilation is not sorted nor will it ever be while there is a perceived problem of battery gassing without some obvious measures been taken.
if gassing was a major issue [I believe it is not] then some radical steps would have been taken already "like a vent in the top of the battery box to the outside" and the placement of the battery box where it would never be enclosed [like on the awning side] assuming the badly overcharged [gassing] battery would vent out of a sealed box through a very small gap around the EHU cable [at the bottom of the box] when as it has been stated the gassed off gasses are lighter than air. is in my view ridiculous as the box would have to be full of gas before any was vented off.
the scenario posted by Royston is rare but not unknown, it is caused by an internal short within the battery that is fueled by the charging process, and in fact consumes the battery from within [the reason it showed only 10v when tested] the same thing happened to me not on the van but in a car that was parked, a passer-by alerted me to it as smoke was coming out of the front grille, I managed to avert a catastrophic incident by cutting through the battery cables. the case was like jelly and took 2hrs to cool down on removing the battery next day it resembled a uncut loaf.
if this happened in the van no amount of venting would help and neither would the flimsy plastic battery box.
one does get tired of these perceived problems that in fact are so rare as to be insignificant from gassing batteries to fumes from the fridge in an awning, and from blow outs on the motorway. to having the house burgled while away in the van. of course there will be worries most unfounded just enjoy your time away. and leave the worries at home.

 

[Gafferbill]

Hydrogen is odourless........what Royston smelt was likely his overworked charger getting hot trying to charge a duff battery.
The risk from Hydrogen produced from a Lead acid battery is that of it exploding .......so ventilation helps minimise this.
Keep any source of ignition away from such a battery and then the risks are minimal as Colin says.

I was sitting in the cab of a truck once when one of it's batteries exploded.
On pressing the starter button the battery disintegrated with a loud bang spraying acid for 10 meters all around.
The cause was a spark from a slightly loose battery terminal igniting the Hydrogen within the battery.

Since then I have not been complacent around such batteries.

 

[JTQ]

Whilst hydrogen is odourless the carry over of sulphuric acid vapours on an over charging battery is not.
As has already been picked up the fact the battery was at 10 volts indicates the cause, one cell had shorted, probably by paste dropping out, leaving 5 cells facing the regulated 13.8 volts, instead of 6, hence boiling off.

I don't accept for a minute a cell shorting is a rare occurrence; plates shedding paste and shorting is a common mode of battery failure.

The use of crocodile clips and snap on battery connectors always gives me the shudders, for the reason given by "Gafferbill", they increase the probability of a spark just near the source of an explosive gas mixture.

 

[ProfJohnL]

...........................
one does get tired of these perceived problems that in fact are so rare as to be insignificant ..........

Hello Colin,

It was part of my job in days gone by to consider the ways in which products might fail - it is a recognised design process and is called a Failure Mode Effect Analysis (FMEA). It is by considering possible failure modes and ranking their likelihood,effect and consequence as part of a design process that has led to several measures being introduced and will have prevented problems for customers when failures do occur. The fact that such processes work is difficult to show without disclosing commercially sensitive information because the incidents they are designed to catch have not developed into reportable issues.

Even if a fault is rare but its consequence is fatal, then you would expect the designer and manufacture to consider action to either prevent the fault from occurring or to manage it as safely as possible.

Lead Acid Batteries do pose a risk when they are charged, or discharged suddenly. This could be either a deliberate or unintentional occurrence, either way an exploding battery is a significant hazard and has the potential to cause major injury or even death.

The provision of dedicated battery compartments in caravans, is not just a cosmetic palliative, but they have an important role to play primarily segregating the chemicals, energy and emissions of a battery from the occupants of the caravan. The cabinet is practical and effective barrier, and if as in the case of the OP the practice should be repeated for the second battery. The same issue applies to the gas bottles, where the possibility of flammable gas fumes must be managed. Nobody questions the validity of the gas precautions.

 

[xtrailman]

This question of ventilation has never really been answered on any forum I've been on.

In theory the ventilation should be at the top, but no one is certain there is any in the standard box.

OH, really. I would have thought it had many times . no part of a caravan is air tight it is hard enough to get them water tight [apparently] so ventilation should not be a problem not even in the battery box. and then there is the charging issue,
a standard EHU will only fill the battery to 80% @13.8v and a solar panel would only trickle charge it, so gassing should not occur even if left perminantly connected,
plus many batteries are now sealed for life. I really cannot see why some see problems when there is none.
does anyone really believe that manufacturers are unaware of a problem if one existed,

Should this should that is an idealistic view point.

Fact is some caravans are fitted with 2 or 3 stage chargers, Swift in particular not that long ago were seeing some go faulty and boiling batteries.
Then we have the scenario where the battery develops a shorted cell, and again boils on a standard 13.8 volt charger.

then we have this 80% charge only myth, a caravan battery will fully charge on 13.8 volts it just takes longer. In practice most people tow the caravan with the car charging over 14 volts anyway. As I do.

My battery is 10 years old and NEVER been on a 3 stage charger.

 

[colin-yorkshire]

...........................
one does get tired of these perceived problems that in fact are so rare as to be insignificant ..........

Hello Colin,

It was part of my job in days gone by to consider the ways in which products might fail - it is a recognised design process and is called a Failure Mode Effect Analysis (FMEA). It is by considering possible failure modes and ranking their likelihood,effect and consequence as part of a design process that has led to several measures being introduced and will have prevented problems for customers when failures do occur. The fact that such processes work is difficult to show without disclosing commercially sensitive information because the incidents they are designed to catch have not developed into reportable issues.

Even if a fault is rare but its consequence is fatal, then you would expect the designer and manufacture to consider action to either prevent the fault from occurring or to manage it as safely as possible.

hello John.
I do not doubt your sincerity or question your professionalism. I only see things from a lay-mans point of view with knowledge gained from a lifetime of experience, this tells me that [if] a perceived hazzard/problem could occur from the possibility of a gassing battery, [then] considering the timescale that touring vans have been made, at some point provisions would have been made to prevent the build up of gas by providing vents into the battery box and/or siting the box it's self in a more robust isolated location, plus they would have made dam sure that gassing did not occur in the first place even if that meant moving away from lead/acid batteries to a more safer equivalent.
the very fact that this seeming has not happend the risk assessment must be very low and therefore insignificant.
While it may be right to point out possible dangers it can seem overdone sometimes, there have been several threads of late in the same vane and one does get [tired] of the constant warnings, if everything did go wrong that could go wrong no-one would enjoy the hobby and it would be a minority sport,
on a personal note having now given up the caravan, I sometimes wonder how I survived 40+ years at it. without been blown up, gassed, run over, electrocuted, injured, or drowned.

 

[RogerL]

There's so much myth and debunking about batteries it's difficult to know where start.

Safety systems aren't designed just to cope when everything is working as it should - they're designed to cope when something fails, as inevitably something will.

Basic observation - batteries need adequate ventilation, no debate, end of.

 

[ProfJohnL]

.................While it may be right to point out possible dangers it can seem overdone sometimes, there have been several threads of late in the same vane and one does get [tired] of the constant warnings, if everything did go wrong that could go wrong no-one would enjoy the hobby and it would be a minority sport,
on a personal note having now given up the caravan, I sometimes wonder how I survived 40+ years at it. without been blown up, gassed, run over, electrocuted, injured, or drowned.

Colin,
Not everyone is blessed with your level of knowledge or skill in handling some of these issues. Don't forget that in times gone by, some aspects of caravanning were not as highly regulated as they are now, and where a suck it and see approach may have been previously adequate,but these days the same issues are now subject to new or tightened laws or better detection.

What can possibly be wrong with providing accurate advice? Its got to be better than many of the ad-hoc or illogical traditions which have been found lacking. And yes it does need repeating, because the same questions seem to recur quite frequently.

You may have gained your experience during the 'simpler' times and that has equipped you to cope with the issues to day, but new caravanners are not so lucky, and they actually face a steep learning curve to avoid legalities biting them.

There have been several instances where a cautionary note on the forum has saved a new tow-er from making a mistake, and that alone is worth the effort of pointing out some of the potential hazards, But its not just about pointing out hazards, more often than not a possible solution is also offered.

I do wonder sometimes how many caravanners would have suffered some untoward experience if we hadn't provided high quality advice.

Now if you find these cautionary notes annoying then simply ignore them. But for those who need the help they can give, we should continue to post as before.

 

[Gafferbill]

........I echo the Prof's post above and agree with every word.

These days social media such as this forum can be a useful source of information.
Those participating have the choice whether to accept any information given and have the ability to check that information from other sources.

We could remind ourselves of the warning stickers that are attached to all modern batteries of the type in question........take a look there will be around 6 or 7 hmy:

Of course caravanning is primarily a leisure activity and is there to be enjoyed.........knowing any dangers involved goes a long way to staying safe.