Routing battery cable through floor and bulkheads

[stringfellow]

I'm working on an aircraft where the batteries (two EarthX) will be mounted under the front seats. This necessitates a run of battery-appropriate cable (2 or 4 AWG) forward to the firewall.

What is the best practice for penetrating through the floorboard and then through bulkheads? I had planned to secure it as frequently as possible with Adels and use rubber grommets on the bulkhead pass-through. Any other tips?

Thanks.

[Jesse]

Looks like you're on the right track already.

[rv7charlie]

Plastic snap bushings might be more durable, long term, than rubber grommets.

https://www.google.com/webhp?sourcei...snap%20bushing

BTW, I *love* the Bearhawk design. Are you building with the original wing, or the new airfoil?

Charlie

[Toobuilder]

Good info in AC 43.13...

Here is what they have to say about the subject:

[stringfellow]

Thanks all.

I like the plastic snap bushings, seems like they'd wear better than rubber.

AC43.13...I should have known. It seems like when I consult it, I don't find what I need, but then when I decide to skip it because "surely it wouldn't cover this"... there it is.

Any issues with running battery cable atop the floorboard if necessary? Also, has anyone use some of that super-flexible automotive battery cable? Looks like it would be easier to work with than MS 16 strand, but I worry the PVC insulator might not be cockpit safe.

Thanks.

[rv7charlie]

Wear & tear would be the primary concern if on top of the floorboard; keeping it from rubbing and keeping feet/baggage/etc off it.

I might worry just a bit about PVC because its melting point is pretty low, but IIRC PVC was the go-to insulation for certified wire back in the 'good old days'.

Welding cable from your local welding supply (or ebay) is hard to beat for high amp cable. It's reasonably priced, very flexible, and insulation is super tough. Wire gauge should be selected to be big enough to handle any current the battery can deliver, so insulation should never overtemp from current load. If you have a fire big enough to burn the insulation...well, it's all toxic, anyway. If you have a well stocked welding supply, or look online, there are multiple choices for insulation. But I just used what was available.

EDIT: The one downside to welding cable is that the insulation is typically thicker than aviation grade stuff. Still a lot more flexible, but just takes more space to run it.

Beautiful build, BTW.

Charlie