# Venting Batteries



## lefty_kris (Mar 24, 2007)

When i bought my M/H it had one 110ah bat in an under seat position (there was no vent) , I have since added a further 110ah bat and relocated them both to a different location. To charge them i have installed sterling Battery to Battery charger (much better than split charging though expensive and supposed to stop any over charging). Bats are selaed Lead Acid

I have not istalled a vent in this area either. Would you recommend installing an outside vent in this area and if so would a drop out vent be enough?

Kris


----------



## 101411 (Oct 15, 2006)

Hi Kris

The batteries when charging give of hydrogen gas. Hydrogen as we all know is much much lighter then air and therefor collects in the roof space of your van. As you have now doubled the number of batteries you have doubled the amount of hydrogen given off. ALL BATTERIES MUST BE VENTED TO THE OUTSIDE OF THE M/H. Dont your batteries have vent tubes on them?? They should have, if they are not long enough go to a pet shop and buy some aquarium tubing or similar and drill a hole through the floor and vent the batteries that way. 

Your m/h if left with the batteries charging for an extended period of time can literally turn into a bomb. Vent you batteries to the outside or cut a big hole in the roof to allow the gas to escape (not very practical but better then been blown up!!)

Dazzer


----------



## lefty_kris (Mar 24, 2007)

Right, I have a Halfords 110AH leisure battery and another (forget who buy now but they look identical) when you say tubes do actually mean like tubes coming off them because i can see neither tubes nor anywhere i would connect them?!?!

With the serling unit if the voltage to the charging sytem gets to high it shut down in theory removing the risk of boiling the batteries, during normaly charging how much Hydrogen is realistically produced, I have a vent in the roof of the van that i always open when cooking, the box the batteries are in is far from air tight would it not naturally disperce?

Do all types of leisure batteries release Hydrogen??


----------



## 101411 (Oct 15, 2006)

Not an expert in batteries (ask Frank sallytraffic he really knows his stuff!!) but the gas given off is enough to blow up your m/h if left unvented and for a longish period of time.

All lead acid batteries give off hydrogen gas when charging (even when driving and been charged from the engine) if a battery is been "cooked" it smells really strong but hopefully your clever charger will stop that happening.

In answer to your question the vent is sometimes a small plastic nipple that sticks out of the side of the top of the battery with (sometimes) a small plastic flexible pipe attached. Not all batteries have them but I always buy the vented ones. I would imagine you can just drill a small hole in the side of the battery at the top and glue a pipe in place (someone on here will either back me up on that or shoot me down in flames!!!) for venting. I would have thought on the batteries without the pipes you will need to somehow stop them also venting from the tops as they would normally.

Come on all you battery experts help me out here!!!

Dazzer


----------



## sallytrafic (Jan 17, 2006)

Just seen the post.

On my 110Ah leisure battery (a very common type often rebadged as various 'makes') there is a small hole about 5mm diam at each end of the battery 'lid'. I have put a vent tube (aquarium source as per Dazzer's suggestion) into each end joined them together with a T adaptor and led one pipe outside. When the battery came one end had a plastic adaptor clipped into a hole the other end was blanked.

Gassing is a natural part of battery charging and occurs as a wet cell lead acid battery is approaching full charge. Anything over 14V or so depending on temperature produces gassing but you won't get a good charge on a normal leisure battery unless for a short time the battery is taken to 14.4V, although this is also temperature dependant.

The gassing comes from the breakdown of the water in the electrolyte and to some extent is reverseable (see recombination batteries). You want to avoid too much gassing or the loss of electrolyte will be a problem. Some types of battery have their chemistry modified and the charge voltage lowered to avoid gassing. One of these the valve regulated type (VRLA) allows the gas to pressurise the container slightly and like gel types has a different charge requirement to the standard wet cell.

Regards FRank

PS you want to know more try here

>Battery University<


----------



## Waleem (Nov 1, 2006)

When I replaced the twin 85 AH batteries in my A class, I noticed that the new ones didnt have vent holes or tubes. When I asked, I was informed that the caravan shop I bought them from no longer stock anything but sealed batteries which dont need venting. Not expensive either.


----------



## Ifor (Oct 21, 2006)

You say the batteries are sealed but they are the type they have at Halfords. I looked at what are presumably the same ones but decided against them because I did not think they were the type that are really sealed which will take a higher pressures of gas and have catalysts in them to help recombine the Hydrogen and oxygen back to water. They did not look right for this and the pricing was too cheap for this type of battery. You are looking at about £100 of one of these at 100 Ah, something like a Delphi marine...

With your Sterling charger you should be very careful, my understanding is that it will do de-sulpherisasion and may push the voltage up to 14.8 which will gas. You are liable to get a buildup of hydrogen at the top of the container you have them in if there is any leakage from the battery. You may be able alter the setting on the Sterling charger to keep the voltage lower but that is not the way Sterling recommend using there charger, they recommend cheap batteries with proper venting and regular checking of the liquid level.

Personally my two 110Ahs batteries (as described by SallyTrafic) are vented, although I had to put the tubing in and drill a hole in the floor myself. They replaces a sealed 105Ah. The positioning is not good as they are in the bottom of the wardrobe with the charger and control circitry up one side above them. Because of this I have fitted some forced ventilation (pc case fans) that switch on when the charge voltage is over 14.2V. So even if the venting tubes come off or I get other leakage from the batteries then the hydrogen will at least not gather in the same place as the potential sparks from the electrical stuff.

Ifor


----------



## sallytrafic (Jan 17, 2006)

I take it Ifor that you use solid state switching for your fan as using a relay anywhere near hydrogen/air mixture is much worse than letting the gas build up.

Hydrogen is a very small molecule and will penetrate materials like concrete, plywood and even glassfibre. We had a small explosion once at work in a battery compartment and the only source of ignition was a 'sealed' relay but with 20/20 hindsight there is 'sealed' and 'sealed' a mm of plastic is no barrier to hydrogen.

When I say small it woke up Cowes. It was at night and the battery was not charging.

BTW when I googled to try and get another source for how hydrogen is used commercially to check for leaks one of the MHF threads that I had previously contributed to came up on the second page- fame at last (if not recognition  ) see it here:
>MHF hydrogen<

Regards Frank


----------



## lefty_kris (Mar 24, 2007)

Ok, well i have a lot of electronics and electrical experience, but got to admit not with batteries so all of this has been a learning experience (a little knowledge can be danerous)!!

Loked at my Halfords Batteries, and they are 'Leisure batteries' however on close inspection i noticed the screw cap for each cell has two small holes in it (which im going to be guessing is for venting much like a regular car battery). From what I have read this seems to be dangerous and quite irresponsible of such a large chain to do but ho di hum, got to work with the problem now.

The batteries are in a box with the charging gear and the inverter (this is the way i bought the van) and a sub from a sound system, so lots of electrical things that im sure if they fancied it could cause a spark (for those of you thinkning Jezus he's sitting on a time bomb i've taken the batteries out for now).

As a solution I intend to Put a four big holes in the side of this box, stick some propex style vents in said holes with some PC computer case fans in. Will put two holes in the top of the box with the fans attached and two holes in the bottom without fans (to allow for air to be pulled around). I understand all im doing in blowing Hydrogen into the living space but this should not be a problem as I never charger it any way but off the alternator and i can leave the roof vent open and it is used every day so it should be well ventilated.

I invite your thought


----------



## lefty_kris (Mar 24, 2007)

Well, just been to Halfords to try and get some info.

The bloke i soke to at the counter didn't really know so phoned up 'the man in the know at Halfords HQ'

When i spok to him he told me that these batteries did not have and did not need venting the gas produced during charging was held in the container and then re-absorbed later on, the only time gas would leak out was if there was physical damage or failure to a cell, the charger was not working properly and tried to over charge one of the cells / on of the batteries failed before another. Regular inspection and maintanence should be enough to avoid disaster.

I can set the sterling for sealed lead acid which has a maximum charge voltage of 14.4V and a floating voltage of 13.65V @ 20C

In addition to this i will still put in two vents and the bottom and two vents at the top of the box to allow for general ventilation.

Sound good to people?


----------



## 101411 (Oct 15, 2006)

works for me!!!!!

Dazzer


----------

