Author Topic: Electrical Knowledge Needed: Amps. v. Wire Gauge  (Read 3158 times)

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Offline burmashave

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Electrical Knowledge Needed: Amps. v. Wire Gauge
« on: July 17, 2007, 04:55:23 PM »
I'm doing some rewiring on my '77 750k, and I'd appreciate some advice from one of our electrical gurus. Essentially, I am rewiring everything inside the headlight bowl because I can't stand what a mess it is. My plan is to use just a few Molex connectors and route everything through them, and I'd like to route all of the ground wires together into a single wire that would be grounded where the coil bracket mounts to the frame.

My question is, what wire gauge should I use for the common ground, and what gauge should I use for the individual wires coming out of the connector (before they are ganged to a single wire)? See pictures:

Molex Connector with Leads (to be ganged together)

 
Connector with Leads Bundled Up

 
Connector with Leads Wrapped to a Common Wire


Note that the individual ground wires would get plugged into the female connector for the above.

I'm assuming a max total load of 25 amps, based on the total fused amperage on the bike. For the connector in the pictures, I used 16 gauge for the individual leads, and 14 gauge for the common wire to the frame. My only question about the 16 gauge leads is whether one is sufficient for the headlight. The chart on this page seems to indicate that my set up should be sufficient.
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'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
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Offline SteveD CB500F

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #1 on: July 17, 2007, 07:48:19 PM »
The bigger the wire, the lower the voltage drop at any given load. So use the biggest (and shortest) wire that you can fit in and looks OK.

That way you eliminate at least one of the areas for loss.
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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge (Solved)
« Reply #2 on: July 17, 2007, 07:52:48 PM »
Thanks. I'll use 12 gauge then.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline 333

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #3 on: July 17, 2007, 08:03:26 PM »
What are you running through the headlight that needs a ground?  Anything more than the headlight and turnsignals/running lights?  The starter and horn also need ground, but only momentarily.  So, if you were to use 2 of those 16 conductors in that molex, you are probably doubling the amount of wire over stock.  I think on most of our era of bikes, the ground that comes into the headlight is a single 18 AWG wire
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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #4 on: July 17, 2007, 09:11:10 PM »
I don't have anything non-stock running through the headlight bowl, but there are a lot of ground wires amongst that mess. Looking at the wiring diagram, it seems that most of the circuitry does actually go through the headlight bowl, although the starter doesn't.

You're right in pointing out that all the circuits aren't on at the same time. I didn't know that there was only a single ground wire running into the headlight bowl.

At any rate, I've changed my plan a bit. Instead of using connectors, I'm going to solder everything. I'll still be ganging up the ground leads, but no connector. It also looks like the neatest way to do this will be to solder and cable up everything behind the headlight.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline SteveD CB500F

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #5 on: July 18, 2007, 03:08:31 AM »
Good move. Less connectors = less opportunity for voltage drop.

BUT

don't try to remove the headlamp shell...
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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #6 on: July 18, 2007, 05:13:59 AM »
Good move. Less connectors = less opportunity for voltage drop.

BUT

don't try to remove the headlamp shell...

True on the less voltage drop, and I could really use anything I can get because my halogen headlight and 3 ohm coils keep my alternator on the edge of just keeping up. The soldering will go quickly, but I need to spend a bit of time thinking out how to neatly cable everything together.

I don't know why, but neat cabling is a pet peeve of mine, and that's the reason why I started this job. Soldering everything will allow me to tie everything into neat bundles.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline eurban

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #7 on: July 18, 2007, 06:11:17 AM »
Right, but (as Steve mentioned) are you going to be able to remove the headlight bucket with everything soldered up?  . . . . On my 78750K project, I run LED turn signals (signals only, no built in running lights) a wickedly bright LED "luxeon" 1157 bulb in my lucas style tailight/brake light, Dyna III ignition, relayed 3 ohm coils and a halogen headlight with the stock wiring harness and I have no issues whatsoever with battery charging.  This was a complete rebuild project and I made sure that all connectors and wires (fuse block in particular, make sure clips are squeezing the fuses tightly and that the fuses are the correct size) were clean and holding together (a dip in tarn x for the copper connectors works well and didn't seem to harm the plastic surrounds).  The alternator wires hidden underneath the shifter cover live in harsh environment and my original ones were toast. I also replaced my ignition switch (aftermarket) and switchgear (oem) with new parts.  Every connector was put together with a conduction improving lube.  Also I use a solid state regulator from Oregon Electrics that works nicely.  I have spent a good deal of time inspecting and testing my electrical system and I  get over 13 volts at the battery at idle with this setup.
« Last Edit: July 18, 2007, 06:14:41 AM by eurban »

Offline oldfordguy

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #8 on: July 18, 2007, 06:35:39 AM »
Burma:
I'm a stickler for neat wiring as well, and the bike I replaced the wiring on I used the molex connector pins only. I also soldered the connectors after crimping them on, and then covered them with waterproof heatshrink. This is pretty close to as good as being directly soldered together, but you can still take it apart without a un-soldering everything.  This is less bulky than the original bullets, and easier to tie up into neat bundles.
Matt

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #9 on: July 18, 2007, 08:56:45 AM »
Here is a chart to use. And an important thing to remember that even most engineers forget is the derating values to use when the wires are bundled as in a wiring harness. If you 2-5 wires combined in a bundle, then the current rating will have to be reduced by a factor of 0.8. A factor of 0.7 with 6-15 wires bundled, and 0.5 for 16-30 wire bundled...

Here is the chart. The variety of ratings per the insulator is to show that the insulator does change with heat. Another important consideration when using wire. Look at the application, the load, and the possible heat that it will see environmentally.

Scott

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #10 on: July 18, 2007, 11:16:00 AM »
Right, but (as Steve mentioned) are you going to be able to remove the headlight bucket with everything soldered up?  . . . .[snip]

I guess I wasn't clear. I'm actually going to solder the cables together *behind* the headlight bucket. Instead of the wires running into the bucket, everything will be cabled up behind it, and the only thing running into the bucket will be a ground wire and wires for the headlight. After I started playing around with the wiring, I realized that there's no need to run the wires into the bucket if I'm going to solder everything.

And that's why I want to do a little pondering before I start cutting anything. There are a bunch of wire cables that come together at one spot. The challenge is making a neat union.

When I next need to replace a component, it will be a pain to deal with, but it will be essentially a splice job. A fair number of electricals are new.

The solder joints will be a bit more exposed to weather than the connectors are in the bucket, but I use heat shrink, and I'll tape everything when I'm done. I'll post pictures when it's finished.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline 333

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #11 on: July 18, 2007, 01:06:02 PM »
Heat shrink and/or tape will not make a weatherproof seal.  Having dealt with RF connections outside, I can tell you that you will have to go the extra mile to waterproof your connections.  Soldering is good, but if water enters, it will follow the wire inside the insulation and corrode.  How many times have we seen this very thing happen to battery cables with soldered on lugs.  Yes battery acid hastens this effect, but electrolisys makes water an acid when exposed to two dissimilar metals(solder/copper alloy).  You may want to rethink your decision on in or out of the H/L bucket.
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Offline oldfordguy

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #12 on: July 18, 2007, 01:33:47 PM »
The heat shrink that I use is specifically for waterproof applications (not the junk you buy at the department/auto parts store.)  It is lined with a waterproof, heat activated adhesive that you can see seep out the end of the tubing when it is shrunk with the heat gun.  Check this link: http://insulationplastics.com/210211.htm  It is available from electrical supply houses such as Mouser, Digikey, etc.  It is a little thicker walled than the ordinary stuff, but for applications exposed to the elements it really makes a difference.
Matt
« Last Edit: July 18, 2007, 01:44:01 PM by oldfordguy »

Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #13 on: July 18, 2007, 05:41:09 PM »
Heat shrink and/or tape will not make a weatherproof seal.  Having dealt with RF connections outside, I can tell you that you will have to go the extra mile to waterproof your connections.  Soldering is good, but if water enters, it will follow the wire inside the insulation and corrode.  How many times have we seen this very thing happen to battery cables with soldered on lugs.  Yes battery acid hastens this effect, but electrolisys makes water an acid when exposed to two dissimilar metals(solder/copper alloy).  You may want to rethink your decision on in or out of the H/L bucket.

Thanks so much. That's a bummer, but it's good to know before I started cutting wires. :-) I'll solder the wires and keep the (now soldered) connections inside the bucket.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline 333

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #14 on: July 18, 2007, 06:19:12 PM »
Now this is just how I'd do it, but I'd replace all the bullets just with new ones, same style.  And when connecting them, use a dielectric grease.  Honda used to sell some, they still might.  This will seal the moisture out, and if it oozes, won't conduct electricity and short.
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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #15 on: July 18, 2007, 07:16:50 PM »
I've replaced some other connectors with vintage bullet connectors. I actually like them more than more modern spade and bullet connectors; however, I did see some nice but pricey 3M bullets that are rated to be highly water resistant.

I don't think I could do a neat job if I use bullets. The sheer volume would likely replicate the mess I'm trying to replace. I really don't mind soldering. I did it for a living once, although it spoiled me in terms of equipment. Now, I feel like my $20 Radio Shack butane soldering iron is a stone age tool compared to the $250 temperature controlled solderer that I learned on. On the other hand, I don't have to use a low power microscope to solder CB750 connections. ;-)

On the topic of weatherizing connections, I've become gun shy of using too much dielectric grease. I once experienced a voltage drop, and I think it was because I used too much dielectric grease right after a thorough cleaning of some white plastic connectors (are all white plastic gang connectors called "Molex"?).

What happened was that I first cleaned the contacts well with contact cleaner, blew them out with bottled air, packed some grease on the female slots, and put it back together. After I put it together, I had no connectivity in one or more terminals. I gave it another cleaning, and all was well.

Mebbe that connector wasn't good, but on the other hand, I think it was TT who pointed out that dielectric grease does not actually conduct electricity, so I've been more careful in how much I use.

I think I'll peruse the electrical supply companies to see if anything turns up.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline HondaMan

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #16 on: July 18, 2007, 07:48:56 PM »
I've replaced some other connectors with vintage bullet connectors. I actually like them more than more modern spade and bullet connectors; however, I did see some nice but pricey 3M bullets that are rated to be highly water resistant.

I don't think I could do a neat job if I use bullets. The sheer volume would likely replicate the mess I'm trying to replace. I really don't mind soldering. I did it for a living once, although it spoiled me in terms of equipment. Now, I feel like my $20 Radio Shack butane soldering iron is a stone age tool compared to the $250 temperature controlled solderer that I learned on. On the other hand, I don't have to use a low power microscope to solder CB750 connections. ;-)

On the topic of weatherizing connections, I've become gun shy of using too much dielectric grease. I once experienced a voltage drop, and I think it was because I used too much dielectric grease right after a thorough cleaning of some white plastic connectors (are all white plastic gang connectors called "Molex"?).

What happened was that I first cleaned the contacts well with contact cleaner, blew them out with bottled air, packed some grease on the female slots, and put it back together. After I put it together, I had no connectivity in one or more terminals. I gave it another cleaning, and all was well.

Mebbe that connector wasn't good, but on the other hand, I think it was TT who pointed out that dielectric grease does not actually conduct electricity, so I've been more careful in how much I use.

I think I'll peruse the electrical supply companies to see if anything turns up.

Who is this guy "burmashave" who fell into my trap?   ::)
Mr. B: I'm an Electronics and Controls Engineer by trade, almost 30 years. Worked in side, oilfield, outdoor equipment, giagantic trucks, sonwblowers, buses, etc., etc., a looong list. Now, it's on airplanes.

Just a couple of things that will go a long way toward a bombproof system (Eurban alluded to some of them):
1. If you can manage to get them, use the gold-plated inserts for your connectors. These will carry more current with less loss, never rust or corrode, and solder perfectly. They cost about $.12 each instead of $.06 each, but worth every $.01 . A single 16 AWG size pin/socket from AMP or Waldom/Molex will carry more current than the 310 watt CB750 alternator can produce.
2. Use LPS-1, just a drop, on the ends of the insulation on every wire that you think might get wet (AFTER soldering). This will permanently prevent ingress of water into the insulation's jacket by capillary action, also preventing the corrosion that results. In the absence of LPS-1, use a drop of non-synthetic motor oil, it's almost as good.
3. Solder every connector on every wire.
4. I would recommend a pair of 16 AWG wires as your primary ground buss to the headlight. You will find 14 AWG to be very stiff and brittle at the crimped connections, and prone to vibration breakage at those points in those types of non-relieved connectors.
5. You will likely run out of physical space by using 16 AWG wires everywhere, and they really aren't needed: the headlight, followed by the coils, are the highest drain in the bike. Size the headlight high beam at (60w/12v=5 Amps, 18 AWG is plenty with a total 5-foot-long circuit) and the coils, if Dyna, at (13.6volts/ 3ohms= 4.53 amps, because only 1 runs at a time, if you use points ignition, 20 AWG is plenty). Mostly, 20 AWG is fine for any of these connections outside of that: use 22 AWG inside the handlebars.

...just my pennies' worth.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #17 on: July 18, 2007, 08:18:30 PM »
Thanks, TT. You're the best. :-)
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline TwoTired

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #18 on: July 18, 2007, 08:27:46 PM »
Thanks, TT. You're the best. :-)

Aw shucks, you figured out that I sometimes log in as HondaMan.   ;D

NOT

BTW, dialectric grease, while it is and insulator, is used to prevent atmospheric gasses from corroding the contact metals.  The contacts should have enough grip on each of the mated pairs to displace the grease where the contact is made.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
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Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #19 on: July 19, 2007, 02:46:34 PM »
TT, I hadn't quite figured it out, but you've given yourself away. ;-)

I think I've found a solution to soldering the connections behind the bucket. 3M (and possibly others) make a "dual wall" heat shrink. The external wall is normal heat shrink, while the internal wall is an adhesive that flows when heated, making a moisture barrier:

3M Dual Wall Heat Shrink Tubing

I've ordered some from Action Electronics. It's about 30% more expensive than standard heat shrink.
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k

Offline 333

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #20 on: July 19, 2007, 05:08:10 PM »
No, I'm Hondaman!!!  And I can prove it.  I OWN a Honda!
Go metric, every inch of the way!

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Offline HondaMan

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #21 on: July 19, 2007, 08:29:08 PM »
No, I'm Hondaman!!!  And I can prove it.  I OWN a Honda!

Yep, see that big red "H" on his chest?   ;D
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

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Offline oldfordguy

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #22 on: July 20, 2007, 11:20:19 AM »
TT, I hadn't quite figured it out, but you've given yourself away. ;-)

I think I've found a solution to soldering the connections behind the bucket. 3M (and possibly others) make a "dual wall" heat shrink. The external wall is normal heat shrink, while the internal wall is an adhesive that flows when heated, making a moisture barrier:

3M Dual Wall Heat Shrink Tubing

I've ordered some from Action Electronics. It's about 30% more expensive than standard heat shrink.

Gee, where'd you get that idea?

Offline burmashave

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Re: Electrical Knowledge Needed: Amps. v. Wire Gauge
« Reply #23 on: July 20, 2007, 11:51:44 AM »
TT, I hadn't quite figured it out, but you've given yourself away. ;-)

I think I've found a solution to soldering the connections behind the bucket. 3M (and possibly others) make a "dual wall" heat shrink. The external wall is normal heat shrink, while the internal wall is an adhesive that flows when heated, making a moisture barrier:

3M Dual Wall Heat Shrink Tubing

I've ordered some from Action Electronics. It's about 30% more expensive than standard heat shrink.

Gee, where'd you get that idea?

Unfortunately, I had to discover it on my own because I didn't read your post carefully enough. :-\ I missed the "waterproof" part about the heat shrink. :-(
Quote from: SOHC Digger, RIP
'Ere's whatcha do, Guvna', just throw a couple dookie logs in the hearth and bob's your uncle!
'77 CB750k