Thread: Aux Battery Cabling

Yes it is and so is daves thats why I mentioned it☺

Speaking of VW beetles and their battery locations,
I well remember the back seat starting to smoke one cold night doing the Rally fan thing.

May possibly had something to do with the 4 Super Oscars on a roof bar & the somewhat dodgy cabling done to the battery.

What?

Groan...

Originally Posted by AndyG

Speaking of VW beetles and their battery locations,
I well remember the back seat starting to smoke one cold night doing the Rally fan thing.

Yep was and is still a problem with the old Beetles.

They came from the factory with a cover positioned over the battery, but the cover itself was not fixed to anything, so people would service or change the battery and forget to put the cover back and the next time they had a passenger in the back!!!!

Originally Posted by drivesafe

Hi Dave and thats fine as long as the top hole is at the highest point it can be, so that if gassing does occur, hydrogen, being the lightest gas, will not pool under the lid.

Can I also suggest, the bottom hole does not have to be much below the top edge of the battery and if possible, put your cable hole where you are planning to, and then put the lower hole, towards the other end of that same panel.

This will increase the area inside the battery box that the circulating air will travel through.

Ok. Having another look/think after reading the above I have more questions.

If I vent to outside my plan was to run some hoses down the side and out towards the back to prevent dust getting in.

Now knowing that the gas is lighter than air I am assuming if the top vent had a hose going down that the gas would just get trapped there.

Now looking at the pic below. If I cut a hole at "a" the gas could then vent into the space "b"

It could the travel upwards behind the trim "c" and get trapped in the top cavity and if it exploded could blow my roof off.

Would this be ok to vent here?

Originally Posted by d2dave

Ok. Having another look/think after reading the above I have more questions.

If I vent to outside my plan was to run some hoses down the side and out towards the back to prevent dust getting in.

Now knowing that the gas is lighter than air I am assuming if the top vent had a hose going down that the gas would just get trapped there.

Now looking at the pic below. If I cut a hole at "a" the gas could then vent into the space "b"

It could the travel upwards behind the trim "c" and get trapped in the top cavity and if it exploded could blow my roof off.

Would this be ok to vent here?

Dave, you are over thinking the problem but that’s because I have not given you all the info you need to know.

Here is a bit of a deviation. Some science for you to ponder.

Hydrogen needs to reach at least a ratio of 4.1% to atmosphere, before it can ignite or explode, but hydrogen will not pool in an open area and will simply mix with the surrounding atmosphere.

As I posted above, the IEEE ( Institute of Electrical and Electronics Engineers ) sets the maximum safe ratio level of Hydrogen to atmosphere at 2%.

A lead acid battery has a given amount of water in it and this means there is a specific total amount of hydrogen that any give battery can produce.

In other words, there is a limit to the amount of hydrogen any battery can produce. If you cause a battery to gas, it doesn’t just produce hydrogen for ever, only some much gas will be produced.

Next, the IEEE also has a calculation you can use to work out just how much hydrogen a given battery size will produce, and the minimum area you need surrounding that battery so that if the battery completely gasses out, the ratio of hydrogen to atmosphere can not reach 2%.

Using their calculations, I worked out I could fit 3 x 100Ah batteries in the rear of my Range Rover, and if all 3 batteries totally gassed out, the hydrogen content of the air in my cab could not reach 2%, let alone the ignition point of 4.1%

Now back to your setup Dave.

If your battery gasses and you have no venting, then because of the VERY small volume of air in your battery box, the ratio of hydrogen will very quickly reach the ignition point.

But with suitable venting into the cab, the hydrogen will instantly mix with the air passing through your battery box and into your cab and it will NEVER reach the ignition ratio.

So don’t worry about all that tubing, just make sure the air can circulate freely through your battery box, job done.