Thread: Defender Devon 4x4 battery tray and optima blue top - terminal spacing

This is what I have to deal with:


The battery tie down is approx 50mm wide, and is centered along the length of the battery.

This goes some of the way to answering the question
https://en.wikipedia.org/wiki/Paschen's_law
I guess we can consider an automotive battery situation to be a Low voltage systems where gas is an insulator.

The complexities arise when other factors such as vibration, excessive moisture, and terminals that work loose are introduced, which I guess leaves physical isolation as the main concern. But even land rover's factory approach of a positive terminal that hangs over the side of the battery (with mega fuse arrangement) would be susceptible to arcing if a sudden jolt was experienced, allowing the battery to slide forward into the front of the seat box.

Still interested in other thoughts and intelligent discussion on the topic though!

You miiiight be reading into this a bit much haha. Grab some raychem heat shrink and heat shrink the bar.

Problem solved.

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I've seen plenty of circuit boards where the 30V and earth busses are separated by a fraction of a mm. Those are in systems without inductance though, so not terribly appropriate to compare.

How about you take a look at the cables on the starter motor? Have a measure of the terminal size and distance to the earthed body of the starter motor. I think you'll find you're worrying about nothing. I would however cable tie some thin plastic over that battery hold down bar to prevent shorting it when you drop a spanner on it.

That's me- making a scientific inquisition into every aspect of it!
I guess it's an addition to the knowledge pool and proof of concept on here in the best case, a meaningless inconvenience to those who replied at worst

It would be easy enough to heat shrink, I've got a heap of the polyolefin (spelling?) Stuff which should work a treat.

Keep the batteries, and do one of the following for your piece of mind..

1 - Heat shrink over the bracket..

2 - Hold down can be scalloped to improve clearance

3 - Make a new hold down out of composite / plastic

Yes, low voltage will need a very small gap before it will arc. Think about stick welding - low voltage, high current - but you need to get a lot closer than 20mm.

I have always thought a plastic (anything non-conductive) battery strap was ideal. Solves any possible issues of arcing and direct contact through movement...