Venting a lead-acid battery under the passenger seat ?

[mattbryson]

I have just replaced my lead acid battery under the single passenger seat, and read that it should be vented to the outside.

Anyone done this?

There is a rubber grommet under the seat with a cable in it, but looking under that its enclosed, cant see any daylight that way.

There is hole covered with silver tape, but I think that is the factory holes for the bench seat, not sure if that makes it to the out side ?

Has anyone done this, or is this not worth worrying about (I've had a battery there for 5 years and its been fine!)

m

 

[T32Rich]

If it's a sealed battery, it should be fine, non sealed create hydrogen when charging and this needs to be vented.
Was it like for like change?

 

[mattbryson]

Almost - its now a Tanya XV110 Powerline - it was the Tanya Enduroline - identical spec and case, but was 30 quid cheaper.

Old one was EXV110 Enduroline Calcium Leisure Battery 12V
new one is XV110 Powerline Dual Purpose Leisure Battery 12V 110Ah

I just noticed though that the Endurline has no access holes at the top and the new one does. So sounds like its NOT sealed.

Crap

 

[mattbryson]

Actually the picture on the site looks like it IS sealed, but it sloshes when you move it....

 

[T32Rich]

Try contacting the supplier and find out if it is sealed. You will still hear electrolyte moving in a standard lead/acid battery.

 

[T32Rich]

Can also be described as maintenance free battery.

 

[airhoguk]

Response from Tanya batteries
Osian (Tayna)

22 Jul 2026, 14:41 BST

Hi,

It does have vent ports, so if the current battery has a vent tube it may be worth holding onto it and putting it in the Powerline.
Kind regards
Osian

 

[mattbryson]

I just spoke to Tayna Batteries and they said it IS Sealed, its just in a case that has the top caps....

 

[Dellmassive]

The factory SLI battery had a 5mm tube that vented underneath

 

[T32Rich]

Just did a search and AI says it's is indeed maintenance free.

 

[mattbryson]

Great, thanks guys.

Just incase anyone was wondering, those holes under the silver tape do lead to the outside, managed to route a breather pipe so its vented now anyway....

 

[RobertO2023]

A lead acid battery inside the passenger compartment must be vented. Even if “sealed” the battery has a pressure relief valve and in the event of a malfunction or overheating the highly toxic / flammable gas will accumulate inside the vehicle. It is very easy to fit a flexible vent tube to atmosphere.

 

[Lubrown]

I remember the old days when the unsealed battery in VW Beetles was under the rear seat. No venting that I recall (apart from rusty floor pans).

Another element of fun - if a heavy person sat in the back and the protective battery cover had been lost (as mine had) then the metal springs under the bench seat could make contact with the terminals by the look of it. I mitigated the risk by banning big boned folk from sitting above the battery.

We’re all still here.

I knew a girl who set fire to hers (accidentally) by nonchalantly throwing her cigarette butt out of the drivers quarter light window… so she thought. It blew straight back in and lit the rear bench alight. I seem to remember what looked like coir and foam in mine so it must have gone up a treat.