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Battery cable size

ScottCC

Member
I'm at the point of running wiring from the aft fuselage to firewall (RV10) and am trying to decide what size battery cable to use. Is AWG 02 good or is 01 better? What amp rating should I be looking for?
Also I'd like to use firewall pass thru connectors.
I'd like to use a pass thru connector that can be insulated but having trouble finding one. Source suggestions?
Thank you!
Scott
 
#2 welding cable, like one of these: https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=#2+welding+cable

Use #6 welding cable for the alternator output.

The RV-14 comes with a nice SS firewall passthrough. Van?s part number is F-00001. http://vansaircraft.com/cgi-bin/store.cgi?ident=1537896306-224-342&action=search

Use a piece of fire sleeve a few inches long on the inside of the passthrough, then a larger piece of firesleeve on the engine side to go over the wires, then a hose clamp to hold it on the outside diameter of the passthrough.

Carl
 
Thanks Carl!
I actually saw that on Amazon but wasn't sure about it. I'll use that (good price too). Didn't see a picture of that firewall pass-thru on Van's...
Thank you...helps a ton.
 
yep

Second that on the #2 cable.

I ended up buying the tefzel wire up front, so I used it. If I had to do it again, the welding cable would be my choice...it's FAR more flexible than the tefzel wire.

I used welding cable for battery and contactor wiring, works good.
 
Thanks Bob,
Bob Nuckolls has a nice description on how to make your own terminals for the connection for cable. May try it.
Thought West Marine had a nice pass thru but can't seem to find it.
Probably get the one from Van's
Scott
 
wow, those look great. Thanks Bob
I wanted one that bolts to the firewall but these look pretty stout..don't look like they'd come loose.
Scott
 
wow, those look great. Thanks Bob
I wanted one that bolts to the firewall but these look pretty stout..don't look like they'd come loose.
Scott

Interestingly that one does not even mention firewall use, unlike the versions from the race care stores.

They label it for "sealing" use.
 
Here are a few things to think about. First, the technique described in the Aeroelectric book is approved for/used in certified a/c, so it must do a pretty good job of fire and CO protection. (Using intumescient caulk will improve performance over the old certified technique.) Next, it removes two connections in a high current feed line. The feed-through devices shown so far seem to have plastic insulators, which will disappear pretty quickly in a fire. They also add the two additional break points (plus the break points for the pair of cable terminals) mentioned earlier.

So, unless you can find some feed-throughs with ceramic insulators, there is risk if there is a fire, and regardless, there's almost certainly going to be higher resistance in the high current feed line due to the extra connections. There's also the reliability question with the added connections.

Not trying to tell anyone what to do; just trying to supply some things to think about.

Charlie
 
I did exactly what Carl suggested. However once I finished all my runs I filled each fitting up with 3M fire barrier too.
 
then...

"...So, unless you can find some feed-throughs with ceramic insulators, there is risk if there is a fire, and regardless, there's almost certainly going to be higher resistance in the high current feed line due to the extra connections. There's also the reliability question with the added connections.

Not trying to tell anyone what to do; just trying to supply some things to think about..."

Then I guess I probably shouldn't say that I'm using electronic fuel injection and ignition, electronic linear actuators for heat valves and oil cooler valve controlled by an arduino, an uninsulated firewall, welding cable for contactor wiring, and firewall pass throughs.:rolleyes::D
 
Blue Sea Systems also sells something similar, which is what I used. It's design intent was for marine use in waterproof bulkheads.
 
I did not build my -10 but there have been flying Learjets for decades. In years past there have been jets lost due to chafing of the un-fused battery wiring. There is now a requirement to check the wiring for chafing during routine maintenence (condition) inspections. All of our un-fused wiring is held tightly in place with Adel clamps and has chafe sleeve over it.

This thread has me wondering if my -10 wiring from aft battery to the starter solenoid is vulnerable to chafing that could cause a fire. Is it common to add any chafe protection to this fairly long wire run?
 
It is common to take steps to prevent wire chafing, no matter what the gauge. Many options available on how to do this. You select the appropriate method based on the specific circumstance.

Carl
 
"...So, unless you can find some feed-throughs with ceramic insulators, there is risk if there is a fire, and regardless, there's almost certainly going to be higher resistance in the high current feed line due to the extra connections. There's also the reliability question with the added connections.

Not trying to tell anyone what to do; just trying to supply some things to think about..."

Then I guess I probably shouldn't say that I'm using electronic fuel injection and ignition, electronic linear actuators for heat valves and oil cooler valve controlled by an arduino, an uninsulated firewall, welding cable for contactor wiring, and firewall pass throughs.:rolleyes::D

Sarcasm is more fun if there's a point to it.

I too will be using an alternative engine controller (that controls an alternative engine, which is a risk I'm assuming you're *not* taking). I, too, have an uninsulated firewall, and welding cable for my 'fat' wires. And after a few careers in electronics fields spanning 4 decades, I don't have many electronic control whizzies because it's no longer that interesting to me and for most of my needs, simpler/lighter to do it manually. Everybody has to have firewall passthroughs of some type. The only reason for my previous post is that someone might be making a choice of passthrough *method* and *device* without knowing (through inexperience or misinformation) all the upsides and downsides of each choice.
 
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Jason, I was actually just looking at that one. How do you like it? are you able to get an insulated cover over it?
 
Sarcasm is more fun if there's a point to it.

I too will be using an alternative engine controller (that controls an alternative engine, which is a risk I'm assuming you're *not* taking). I, too, have an uninsulated firewall, and welding cable for my 'fat' wires. And after a few careers in electronics fields spanning 4 decades, I don't have many electronic control whizzies because it's no longer that interesting to me and for most of my needs, simpler/lighter to do it manually. Everybody has to have firewall passthroughs of some type. The only reason for my previous post is that someone might be making a choice of passthrough *method* and *device* without knowing (through inexperience or misinformation) all the upsides and downsides of each choice.

My comment wasn't meant as an attack of any kind...sorry but there is no tone in this type of communication.

After several reply drafts I came to the conclusion that debating this isn't worth it.

Everyone must do their own risk assessment and decide what is above their "safe" threshold.
 
Jason, I was actually just looking at that one. How do you like it? are you able to get an insulated cover over it?

I really like it and yes, a boot does cover the terminals very well. I ended up putting a stainless doubler along with nutplates on the inside of my firewall.
 
I did not build my -10 but there have been flying Learjets for decades. In years past there have been jets lost due to chafing of the un-fused battery wiring. There is now a requirement to check the wiring for chafing during routine maintenence (condition) inspections. All of our un-fused wiring is held tightly in place with Adel clamps and has chafe sleeve over it.

This thread has me wondering if my -10 wiring from aft battery to the starter solenoid is vulnerable to chafing that could cause a fire. Is it common to add any chafe protection to this fairly long wire run?

I was concerned about that #2 wire under the mostly riveted baggage floor and rear seat.

I slipped fairly thick PVC tubing over the cable before I pushed it through the space under the seats/baggage and also used Heyco bushings at the rear seat bulkhead.

I used the correct Mil-spec wire, but only because I had it given to me during my -6 build. It's stiffness makes it harder to work with :)
 
Don't want to get into this debate, but I'm a die hard fan of Tefzel wire, the insulation properties far exceed welding cable in every regard, I also won't use a non-tin plated wire due to corrosion issues with bare copper. The aircraft industry switched to Tefzel a long time ago for good reason.
 
Don't want to get into this debate, but I'm a die hard fan of Tefzel wire, the insulation properties far exceed welding cable in every regard, I also won't use a non-tin plated wire due to corrosion issues with bare copper. The aircraft industry switched to Tefzel a long time ago for good reason.

Walt,

I too figured Tefzel wire was a better choice than welding cable - until I put a torch to a sample of each. The welding cable faired much better.

Carl
 
Relocated Starter Relay

I also worried about a fat #2 unfused always hot cable in the belly of my RV-10 project My answer was to relocate the starter relay next to the battery, which is behind the baggage bulkhead. The master relay is also there. A fused #8 wire connects the battery to the forward primary bus through the master.
 
I too figured Tefzel wire was a better choice than welding cable - until I put a torch to a sample of each.
I commend you for actually testing both cable types. That's what being "Experimental" is all about.

For the record, I used 2/0 (not #2) aircraft (not Tefzel) cable because my Sky-Tec starter draws around 400A. I actually checked it with a 500A shunt. My cable runs are short so the weight difference is insignificant. It's one less thing I have to worry about.

We could also get into crimping vs. soldering <evil grin>.
 
Walt,

I too figured Tefzel wire was a better choice than welding cable - until I put a torch to a sample of each. The welding cable faired much better.

Carl

An interesting test, but until you inhale the fumes from burning versions of both from within a closed environment, you don't know which will kill you faster. No susch thing as non-flamable and flexible electrical insulator. The key is reducing the time that it takes for the fumes to kill you. I assume tefzel is similar to teflon and the gases produced from teflon under flame are WAY less toxic than PVC, and much smaller quantities of fumes are produced. "Time to death" is substantially prolonged when inhaling burning teflon over PVC. Within a confined space, no one cares which burns faster or more completely, its all about the toxicity and quantity of the fumes and reducing the time from exposure to death. I am sure this why Dan preaches ceramic thermal insulators instead of plastic or rubber based stuff.

This is why any non-conduited wire in a plenum ceiling (typical for commercial office space) MUST have a teflon insulator. Absolutely no PVC allowed. As you may have guessed, I spent many years in the telcom business involved with low voltage wiring.

Larry
 
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Aaand... what does pvc have in common with welding cable?

I am guessing welding cable has a rubber insulator, though I suspect some are PVC. Pretty confident that the welding cable I just purchased for my Tig welder is a soft PVC. I simply don't know. While I am only familiar with the effects of PVC, I have seen rubber burn and it gives off a LOT of smoke. However, I cannot speak to the toxicity of it. This was why I referenced that a better test is inhaling both to determine effects (tonque in check of curse - much research data is available). I was just pointing out that how two samples look after burning them isn't the key factor to consider for fires in confined areas. I am somewhat confident that if rubber were a safer insulator with less toxic burn characteristics for a confined aircraft cabin that it would be specified instead of Tefzel. I am pretty confident that Boeing has done this research (they would be open to major lawsuits if they didn't) and they don't use Rubber insulators on their wire and from my experience I have a high confidence they don't use PVC. I am guessing they use Tefzel.

Larry
 
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Here's a quick link to some insulation properties:
https://www.performancewire.com/insulated-wire-protection/

All the current (pardon the pun) welding cable I've been able to find has EPDM insulation, chosen for both toughness and extremely wide temperature range (makes sense for lying on frozen ground on a construction site and having hot welding slag falling on it).

The stuff I've read (written by folks with decades of experience in the certified a/c world) indicates that *any* insulation will give off significant quantities of toxic fumes once it gets hot enough to start burning; the trick is to use high temp stuff, and minimize the risk of temps ever getting that high.

The worst thing I've seen about PVC is that some versions will sustain a flame once they start burning, while tefzel & some others self-extinguish when the flame source is removed.

Again, the stuff I've read indicates that teflon didn't last very long as an a/c wire insulation because it 'cold flows'. In a mechanically stressed environment, the wire can actually migrate through the insulation.

The one potentially significant downside to welding cable is space; the EPDM insulation is a lot thicker than tefzel.

I'm certainly no authority, but the info is available on the interwebs, if you're willing to dig a bit.

Charlie
 
Temps

It looks like the epdm insulation is good for 105c (221f) and the tefzel for 150c (302f).

I used tefzel for most everything fwf. I used welding cable in the back for the contactor wiring due to its better flexibility.
 
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