Industrial Oppos - I call upon thee for help

"HammerheadFistpunch" (hammerheadfistpunch) 04/02/2019 at 14:07 • Filed to: halp

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I want to get power through my roof on the land cruiser and I need it to be disconnectable and waterproof. I’ve been hunting around for a little while and while there are plenty of choices out there Im having a tough time finding the one that will suit my needs and am in need of help.

The idea is to have 14-16 AWG wire from a fuse block in the back to run up the d pillar and into the space between the headliner and the roof, then a through bulkhead connector with no fewer than 4 pins and no more than 8 to go up through a hole I drill in the roof. Obviously the main thing is that this hole is sealed to prevent water ingress. Then on the outside an ip67/68 rated connector that mates with the bulkhead connector. Ideally thins connector can’t stick up more than, say, 2 inches and it should have an optional cover to keep it waterproof when disconnected.

Also it needs to be able to handle the amps.

!!!error: Indecipherable SUB-paragraph formatting!!! seems ideal, but it doesn’t look like it can handle the amps or wire gauge.

I’ve got a single 40 inch dua l row lightbar that’ s going to go up there, as well as a very low amp light strip and 4-6 low amp lights.

My guess:

16 amps for the lightbar

1 amp for the LED strip

8 amps for the pod lights.

Boy thats a lot more than I thought actually. Call it 35A @12v to be safe.

I’d really like to drill one hole, not a grundle but I am open to 2 (low amp, high amp).

Anyone have any good ideas?

functionoverfashion > HammerheadFistpunch 04/02/2019 at 14:19

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This is probably totally overkill, but what about a marine shorepower “inlet” like this:

I mean, these are rated for 30A at 120vac so waaaay overkill. But this is the first thing that came to mind, with the little door that seals shut when it’s unplugged. 

Sovande > HammerheadFistpunch 04/02/2019 at 14:19

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I don’t know a thing about electricity, but have you looked into fittings for boats?

RamblinRover Luxury-Yacht > HammerheadFistpunch 04/02/2019 at 14:26

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If you have multiple wires or cables that need to go through the same hole, use a multi-wire strain relief.

http://www.elecdirect.com/cord-grips-strain-relief/multiple-hole-cord-grips

If you expect to have them bundled or within a common sleeve, use a single strain relief or a membrane strain relief.

They can be connected through sheet metal (using what is basically a conduit nut), but they’re designed to thread into NPT fittings. So you’d use a bulkhead fitting, and thread the strain relief into that.

RamblinRover Luxury-Yacht > HammerheadFistpunch 04/02/2019 at 14:28

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For the membrane style I was referring to:

http://www.elecdirect.com/cord-grips-strain-relief/heyco-solar-masthead-cable-glands

Tekamul > HammerheadFistpunch 04/02/2019 at 14:31

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DC-DC convert up to 60V , then you only need 7A!

TorqueToYield > HammerheadFistpunch 04/02/2019 at 14:36

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Is 16A right for the light bar? 16A is a lot, at 12V that’s like 200W.

You’re going to have trouble finding any 12V connectors that can handle 35A. If you do find one it’s going to be expensive.

You might be better running cable through a IP68 grommet with a small IP68 junction box with removable cover on the outside.

HammerheadFistpunch > Tekamul 04/02/2019 at 14:38

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and new lights...

Tekamul > HammerheadFistpunch 04/02/2019 at 14:48

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Naa, just bring it back down on the other side.

Seriously, though, that’s a lot of watts to move from the interior to the exterior. It isn’t easier to do this all at the fender and up the A-pillar , and just run the relay controls through the fire wall? Drilling holes in roofs rarely works out. 

vicali > HammerheadFistpunch 04/02/2019 at 14:55

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4 pin connectors?

https://www.amazon.ca/dp/B071XTBZK4/ref=sspa_dk_detail_0?th=1

Sampsonite24-Earth's Least Likeliest Hero > HammerheadFistpunch 04/02/2019 at 15:03

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Spamfeller Loves Nazi Clicks > HammerheadFistpunch 04/02/2019 at 15:10

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Need some more details on your available fusing and relaying. Is that free-for-all or factory integrated desired?

35A @ 12V, you need more than 4 conductors or you need larger conductors for sure. But I need to know the fusing situation to describe how to do it. I’ve moved significantly more than that outboard (66A @ 12V) but if you want to reduce conductors you have to increase diameter very quickly.

HammerheadFistpunch > TorqueToYield 04/02/2019 at 15:11

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yes, 200 watts is pretty common for this size of bar, that being said I have mine fused at 15 amp right now and it doesn’t get hot at all so Im guessing its actually quite a bit lower in practice.  I need to get an ammeter hooked up to it

HammerheadFistpunch > Tekamul 04/02/2019 at 15:13

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I already have holes up there from the port installed rack so its not going to get worse, but if I can avoid doing much more than one big hole that would be ideal.  

HammerheadFistpunch > vicali 04/02/2019 at 15:13

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Thats what all my interior connections are going to be, but I want something that’s not just floppin around up there. 

HammerheadFistpunch > Spamfeller Loves Nazi Clicks 04/02/2019 at 15:15

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Im putting a blue sea panel with a common earth right in the passenger side quarter panel so the run is relatively short and its independently fused components.  

vicali > HammerheadFistpunch 04/02/2019 at 15:36

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Anything planned up there other than lights?I would keep it simple and avoid putting holes in the roof. Can you not sneak up the D pillar and out the hatch seal?

Otherwise doing the IP68 glands is the proper way to do it; shame to drill though.

I don’t think your Chi-ebay bar is drawing 16A.. do your other lights dim when it’s on? When I had 4x 50w hellas up front you heard the engine strain when they were all lit..

HammerheadFistpunch > vicali 04/02/2019 at 15:43

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yeah, I honestly think its less than 10A but even if we make that assumption then its still a 20A connector.  

MM54 > HammerheadFistpunch 04/02/2019 at 16:06

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Cable glands if you want semi-permanent, if you want to unplug it from the roof, Amphenol makes some nice IP67 panel-mount connectors but expect to pay for them. https://www.alliedelec.com/circular-connectors/circular-connectors/?a10=Amphenol%20Industrial

HammerheadFistpunch > MM54 04/02/2019 at 16:07

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I’ve been eyeing those.  I don’t mind paying for good stuff.  I’m only doing this once. 

Spamfeller Loves Nazi Clicks > HammerheadFistpunch 04/02/2019 at 16:09

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OK, you’ve got a couple problems here, but they’re solvable. Issue one, you need more pins.

Bar, strip, and pods all need separate fusing. They just do. To achieve this without making your life hell, you need more pins. And here’s where things start going pear-shaped. You want 1 connector, but, this is best done with 2+ because of the wildly divergent loads. But we can do it in 1.

So, you’re going to need... assume single 12V supply per, and a common ground path, gives you 5 pins. DIN would work great here. You don’t want IP67 though; you want IP68. It’s roof mounted. Assume rain equivalent to 1.5m deep / 30 min.

Using my datacenter calculator I take your 25 @12 and turn it into 2.5 @120, plug in a 3ft, allowable droop not to exceed 3%, then re-rate for 90C (you must rate 90C+ for automotive use!!) and you need 14ga or 12ga there.

14ga AWG is 0.0641in, so yeah, no. 12ga @ 0.0808 / 2.05232mm^2. Don’t sweat it, just making it nice and round for ease of connectors.

So what you want is a 5 pin connector (yes you could carry it on 2, but don’t do that, seriously.) With a wire crimp diameter for 12 ga. That’s really not a big connector at all.

MasterMario - Keeper of the V8s > HammerheadFistpunch 04/02/2019 at 16:16

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How about a trailer socket and plug?

https://www.curtmfg.com/towing-electrical/plugs-and-sockets

Probably not the most elegant solution but I think they should be able to handle the current demands.

HammerheadFistpunch > Spamfeller Loves Nazi Clicks 04/02/2019 at 16:16

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I think you and I are thinking on the same lines.  I was thinking 4 pin (1 common ground and 3 loads - lightbar, lightstrip, camp lights) why 5?

Snuze: Needs another Swede > HammerheadFistpunch 04/02/2019 at 16:33

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RootWyrm is all over this.  Listen to him.  I came to suggest IP68 rated Amphenols.  If it’s good enough for a nuclear submarine, it’s good enough for you!

Spamfeller Loves Nazi Clicks > HammerheadFistpunch 04/02/2019 at 16:39

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5 because of thermal derate and load derate. Rule of thumb on AC and DC is 80% of fuse/breaker across the wire. Therefore, the 16A+ light bar load should be split across two wires and two pins (but should be single fused at 20A or 25A) with the other loads being safe on single pin after temperature derating.

Breaking it down: single pin optimal capacity is 28A. Thermal derating should drop that to about 20-22A in strong sunlight and/or sustained load. Breaker/Fuse derate of 20% takes that to 16-16.4A, or well within 5% margin. Anything under 5% wire margin for constant 12V supply should be considered unsafe and increased or split.

I don’t have the math handy but it’s a hefty chunk going 90C->105C. Remember, inside the insulation is hotter than inside the car. By a lot. Unfortunately I don’t have my 105C derate tables anywhere I can find at hand. But hot day in the sun, you could easily see 105C on the conductor.

That should give you a minimum 15% margin on all 4 power pins at 105C with the ground located in the center. Also note that I am very deliberately going slightly  above minimums here in part because of the lightbar draw uncertainty. I would assume for the lightbar closer to 20A.

HammerheadFistpunch > Spamfeller Loves Nazi Clicks 04/02/2019 at 16:42

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Breaking the load into two pins. Got it. That’ s what I was thinking but I was just wondering. my problem now is finding a 5 pin I like that meets my other requirements.

So to ask a simplified question with complicated answers - most of these connectors are rated for only 5-10 amps @ X volts.  I don’t know enough about that rating to know if that’s total max amps, or if thats amps at those volts but more amps at lower volts? or amps per pin?  Any guidance there?

Spamfeller Loves Nazi Clicks > HammerheadFistpunch 04/02/2019 at 17:11

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5 pin’s a pretty common configuration, so that part should be easy. Or get more pins. Nothing wrong with future expansion!

Lucky for you I’m around though, because I have complicated answers for complicated questions on tap.

https://blog.samtec.com/post/connector-voltage-and-power-rating-101/

(Samtec is one of my tier 1s.) The shortest version however, is this: you need three ratings to know if a connector is appropriate. Breakdown, DWV, and Working Voltage. Breakdown is where insulation fails catastrophically, DWV is the maximum peak, and working is the maximum continuous.

These will come with TEMPERATURES! Oh goodie.

You need the TEMPERATURES to understand the current. Current is limited first by ambient over contacts. Contacts do not scale linearly! (There will be a quiz.) Doubling current creates quadruple the heat rise; it’s logarithmic. At 50% of contacts, it will carry 75% of the maximum per contact, at 100% energized it will carry approximately 60% (and will not derate below that for a quality connector. Avoid China like the plague here.)

So what this means is: you need a connector which can support about 42A @ 60C ambient (about 140F) at 80% energized. Wires need to support more because of the significantly higher inside temperature and heat rise. If you exceed load for the ambient, the connector must fail safely! Inside wiring will NOT fail safely, by default the connector WILL because it will deliver less current without a marked increase in resistance.

I promise you, this all makes way more sense if you read a few of Samtec’s articles on the topic.

HammerheadFistpunch > Spamfeller Loves Nazi Clicks 04/02/2019 at 17:29

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Im not going to lie, thats interesting reading but I can’t say im any clearer on a solution to my problem. It sounds like I need to find a connector that is an order of magnitude more robust than the ones I’ve been seeing.  Like I was saying, most of these connectors are rated at 5- 10 amps, not 50+.  Im just having a hard time getting my head around the idea that I can’t find a connector that can power a single light bar and a few tiny low power lights.

diplodicus forgot his password > HammerheadFistpunch 04/02/2019 at 20:07

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Whatever you decide on as far as shell size, pin configuration cross reference with Fujikura connectors, cooper has some as well. One of the two is typically a little cheaper than amphenol but they meet the same military specs

https://galco.com/shop/Fujikura-Formerly-DDK-Circular-Connectors

RacinBob > functionoverfashion 04/05/2019 at 07:34

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This plug set seems to be pretty sweet. It would allow far more power than 200 watts, i t is gasketed and looks to be easily sealed , has a positive lock for the plug. almost flat closed, probably UV resistant. It provides 2 circuits and a ground and if you wanted a third and 4th circuit , just install a second one.

RacinBob > RacinBob 04/05/2019 at 07:36

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The only worry about it is someday a dummy thinks it’s a charging port for your car and plugs a hot 110 vac extension cord onto it. That will be exciting,