# Do batteries need breathing space



## Webby1 (Mar 11, 2012)

We have 2 leisure batteries situated centrally in the van in a large underseat compartment with the powerbloc and RCD.........and not much else.

Always looking to redistribute weight and it looks an ideal space for some heavy items such as my toolbox.

Provided they are properly secured and not interfering with the connections etc can they sit on/around the batteries or do they need breathing space.
Thanks


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## Mrplodd (Mar 4, 2008)

So long as anything extra is well secured (so it cannot interfere with/short circuit/damage anything) I cannot see a problem. There is no airflow present at the moment so any additional. Items will not affect it!


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## pippin (Nov 15, 2007)

However, you may not want to put items that might be affected by sulphur (or sulfur if from USA!) fumes into the battery locker.

Unless of course the batteries are vented to outside via the little pipe on the top.

Before you pack anything really tight around the batteries you may wish to test the temperature (by palm of hand contact) when they are being charged heavily after discharge.

A duff cell can get very, very warm leading to thermal runaway.


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## Pudsey_Bear (Sep 25, 2008)

It might be wise to have some sort of vent in there, and if lead acid, you might need to provide a hole for a breather pipe.


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## listerdiesel (Aug 3, 2012)

It's not as easy as that.

Batteries heat up and cool down during their normal cycles, and anything that prevents this happening, especially preventing cooling, is not a good thing.

Reason: Batteries have a set charge voltage that is tied to their ambient temperature, and this voltage decreases when they get hot and increases when they get cold.

Temperature compensation is important at elevated temperatures.

If your battery gets hot and doesn't receive a corresponding lower charge voltage, a condition will exist called thermal runaway, where the battery puts the excess charge into heat, the charger keeps on pumping more in which the battery puts into even more heat, and then in extreme cases you'll get meltdown.

All lead-acid batteries have temperature compensation graphs available for them.

So it is not a good idea to pack around batteries with other gear, radiation is one of the few methods the battery can use to shed heat in the absence of any cooling airflow.

Peter


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## cabby (May 14, 2005)

I thought it was standard practise to have a venting tube going down through the floor to vent the batteries, if not then suggest you do it now. 
providing you leave room or a space enough for the batteries to be warm without causing any damage then yes by all means put more stuff in the locker, but make sure it cannot spark or ignite any fumes that may linger in the locker and of course nothing inflammable.

cabby


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## Pudsey_Bear (Sep 25, 2008)

Some batteries don't need a breather tube though, sealed for instance.

My VB box is under the floor and is well ventilated, the LBs are under the driver seat so in a large space.


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## Webby1 (Mar 11, 2012)

*Sealed batteries*

Thanks for your replies.

As far as I can tell the batteries are sealed with no vent tube and in a large compartment under the dinette seat...........its a lot of wasted space in the middle of the van so good for heavy items..............just want to sit a few things around them rather than packing them in tight.

Anyway........thermal runaway sounds pretty serious..............but then again so did reversed polarity until I got a better understanding of it.

I've got one of those point and shoot LED temperature gauges which is another unnecessary toy(but great fun) so I'll keep an eye on the temperature


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## cabby (May 14, 2005)

I would take note of the points Peter has raised and use a bit of common sense when putting more items in the locker.

cabby


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## listerdiesel (Aug 3, 2012)

Battery venting is another can of worms  

A sealed battery needs no venting, BUT:

If the battery is over-charged or over-discharged it will vent water vapour and/or Oxygen & Hydrogen through the pressure vents. Any loss is permanent so a bad thing.

Vented (wet) batteries will give off gases in their normal operating cycles and do need a proper vent tube to the outside air.

In both cases, an amount of sulphuric acid will carry over, so I'd always try and keep them away from anything likely to be damaged.

Most sealed batteries have NO provision for a vent pipe, a few wet batteries will have, but generally not that common.

Peter


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## vicdicdoc (May 14, 2005)

Satisfy yourselves & everyone else by leaving around 4" space around the batteries . . They keep cool, you keep calm - simples :silly:


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