Simple Wiring Question

[Smacdab]

Hey everyone. I'm pretty clueless about details on electrical circuits. But I'm looking to set up heated gear (jacket, gloves, socks) on my motorcycle. The gear that will draw about 10 amps. The circuit, of course, issues s 12V battery. Using what I have lying around, my plan is to run about two feet of 18 gauge (4 feet total round trip distance) wire with a 15 amp fuse, on its own dedicated circuit. I don't think this past matters but's an SAE connector battery tender cable, connected to the heated gear through an SAE to coax adapter.

Is this plan safe? More specifically, is the 18 gauge wire enough for this?

Thanks for the help.

 

[Smacdab]

OP here. Wow, sorry for all the typos in my original post. Since I don't see a way to edit that post, here's a corrected version:

******

Hey everyone. I'm pretty clueless about details on electrical circuits. But I'm looking to set up heated gear (jacket, gloves, socks) on my motorcycle. The gear will draw about 10 amps. The circuit, of course, is on a 12V battery. Using what I have lying around, my plan is to run about two feet of 18 gauge (4 feet total round trip distance) wire with a 15 amp fuse, on its own dedicated circuit. I don't think this part matters, but's an SAE connector battery tender cable, connected to the heated gear through an SAE to coax adapter.

Is this plan safe? More specifically, is the 18 gauge wire enough for this?

Thanks for the help.

 

[Audioguru]

Does the generator/alternator/voltage regulator supply enough current for the heating plus everything else?
Do the heated clothes have an automatic temperature controller? Or you simply use an on-off switch?

 

[Smacdab]

Yes, there's enough power to run everything (heated gear plus other devices drawing current). Yes, the heated gear has a temperature controller.

But my question is really about the wiring. I know that the draw from the heated gear will be about 10 amps with everything set to maximum heat. And the heated gear will be on its own dedicated circuit drawing from the 12V battery. So my question is: is 18 gauge wire strong enough to handle this safely?

Thanks for any help anyone can offer.

 

[Audioguru]

I have never wired high current. Lookup a list of wire guage spec's.

 

[Bluejets]

Seems it would be around 0.5v drop....

calculator here ...... https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html

I'd be using silicon cable as used in rc model aircraft with some form of outer sheath for protection, much more flexible.

As far as safe is concerned, only as good as your connections and any mechanical protection you have in place.

I'd tend to be looking at some form of quick disconnect, not so much for any electrical fault that may arise but mainly for when you dismount.
Any secured cable you forget to disconnect beforehand ( and it will happen) will near tear your head off or have the bike come crashing over.

 

[Smacdab]

Thanks! So in plugging the numbers that I think are applicable into that calculator, I get the following. I'm not sure how to interpret this, though. I've seen things online saying that in general applications, a voltage drop of less than 3% is acceptable. Does this mean I'm ok?

BTW, I'm interpreting the "one way" cable length to mean half of the round trip of the circuit, meaning from one terminal of the battery to the load. I'm talking about a total of four feet of cable (2 from positive of battery to load and 2 from load back to negative of battery), so I think 2 is the number the calculator is looking for.

So, think I'm ok?

Re: quick connectors, yeah, I'm fine. Thanks, but pulling the bike over will not be an issue.

 

[Bluejets]

Yes, my error.
Didn't see the (1 way)

The actual voltage drop is something you need to consider when connected to your equipment and whether or not the load can tolerate it.
In your circumstances it wouldn't matter a toss as it's just heating elements.
The only problem would be if your cable is too small to handle the maximum current, it too will become a "heater" and possibly burn connectors.
In your instance, 250mV is nothing .....
I'd be more concerned about the maximum current the generator system can provide.
Normally they don't include massive (10A extra) capacity in bikes.
Maybe a small margin with everything turned on.......but 10A, I doubt it.

2 ft....???? are you sure this is the route length??
You said jacket,gloves, and socks etc....seems it would be much more than what you say unless you are REALLY short.
For me, that would barely get from the battery to my butt....

 

[Martaine2005]

unless you are REALLY short.

 

[Smacdab]

Ooooh, good point about two feet. I was thinking two feet from the battery to the ends of the wiring that connects to the jacket at the waist. But is it likey that there is wiring throughout the jacket that is also part of the circuit? Or does the current from the battery just go to some sort of unit at the jacket's waist, which in turn heats the rest of the jacket without making the rest of the jacket part of the circuit? As you can see, I'm pretty clueless electronically, so thanks for any help.

Also, power availability should be ok. Stator puts out extra 100W of available power plus I've swapped out stock headlight for LED for some extra juice. Will be close, I think, but manageable.

 

[Bluejets]

mmmm...well say Honda 750, probably has around the 220w output and different ones have been trying to increase this over the years.
Seems around 30w is the maximum they can achieve with major hacking.
100w extra to me seems a bit of a pipe dream really.

 

[Tha fios agaibh]

I would be careful about the type of wire your using.

18 awg wire with pvc insulation is only rated for 7 amps. 18 awg wire with a higher temperature rating such as Thhn insulation is good for up to 16 amps.

Make sure you are not using a fuse larger than the ampacity of the wire you have.

 

[Sidecar Bob]

Speaking as someone who has driven sidecar outfits in the winter for the last 34 winters and never felt the need to use electrically heated clothing, I can't understand why anyone would need enough of it to draw 10A.
But if you are planning an arctic expedition or something like that and really need it 18AWG wire should be fine. The table below tells you what size wire you need for the current and length and it says that your 4 feet of #18 can handle up to 24A (although if I needed that much current I think I'd use something heavier if only for lower voltage drop).

My biggest concern is whether your alternator can supply that much current while powering the lights, ignition and any other loads and have enough left over for charging the battery.
What kind of bike do you have?
What are its alternator's ratings?
What other electrical accessories does it have?
Will you be using it at in town or highway speeds?

 

[davenn]

I know that the draw from the heated gear will be about 10 amps with everything set to maximum heat.

well 12V x 10 A = 120W ..... that's a hell of a lot of power !!
I

 

[Sidecar Bob]

FWIW, the only electric heaters I use for winter biking are handlebar heaters (they make a huge difference). I got mine before they started making them with dual heat so I use a DPDT centre off switch so that they are in parallel when the switch is up (high heat, 36W total) and series when the switch is down (low heat, 9W).
I consider that 36W to be a pretty hefty load for the bike's 250W alternator but some bikes have 700W or more alternators so 120W of heat is feasible.

On the other hand, it has to be pretty cold out before I start to feel chilly in my snowmobile suit and I don't have to unplug it before I get off the bike.

 

[Smacdab]

Big thanks, all. Ok, responding to a few points here -- hope this clarifies a few things.

- The bike is 2020 KTM 690 Enduro R. Its stator puts out about 225W of power. About 125 of that is taken up by the bike's needs without mods (ignition, electronics, lights, etc.), which leaves 100W for mods. I've replaced the stock headlight with an LED, which gives me a a little more available power. So my 10A draw is going to be iffy, but I'm prepared to deal with it by turning off the gear at low RPMs, turning off other accessories while I'm using it, etc. I know other people have used this heated gear on this bike successfully.
- The 10A estimate for the draw from the heated gear comes right from the manufacturer, Gerbing. Check out their website for the total draw of jacket liner, socks, and glove liners = 9A. Here's what they say to use to use for calculations (numbers are in amps):

- Heated gear is very common for motorcyclists who ride in cold weather, especially those who do long distance, multi-week (or much longer) adventure riding that can often involve huge swings in temperature from one day to another, or even one hour to another, as elevation and other factors come into play. A single trip often involves temps both in the 90s and the 20s. Space considerations are also a major consideration for us when it comes to packing, as we're riding smaller "adventure" bikes rather than the big street bikes (think Gold Wings or Harleys) that have huge packing capacity. So snowmobile suits and the like are off the table for us. Heated gear is very effective and takes up very little space.
- Great chart, @Sidecar Bob . Interesting that I also found this one at http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/:


I think the difference between the two is that this one is assuming 13.8V, which of course is the actual output of a 12V vehicle battery when running at highway speed. Looks like 18 gauge might not be quite enough . . .

Again, big thanks to everyone for the help!

 

[Sidecar Bob]

The chart I posted is for 12V vehicle applications so it assumes that a nominal 12V system is actually 14-15V when the engine is running fast enough for the alternator to produce full output (usually over 2500 or so RPM).
The one you posted looks like a simplified, much more cautious version based on it.

It's up to you whether you use that much heated gear BUT if my alternator only produced 225W I wouldn't even consider it.

 

[Smacdab]

The chart I posted is for 12V vehicle applications so it assumes that a nominal 12V system is actually 14-15V when the engine is running fast enough for the alternator to produce full output (usually over 2500 or so RPM).
The one you posted looks like a simplified, much more cautious version based on it.

It's up to you whether you use that much heated gear BUT if my alternator only produced 225W I wouldn't even consider it.

I meant to mention: I have a voltage monitor running, so if I see things dipping below 12V (and yes, that's certainly a possibility given that I'm cutting it close) I'll shut 'em down (the heated gear, I mean).

 

[Martaine2005]

Personally, I’d give the wire a little headroom. 16awg is a fraction more expensive. And you’ll be surprised how the small distances add up. It’s not calculated just to the connector.
Plus, I think it’ll be just fine on the bike. Remember, you’ll never have full beam, side lights, brake lights, horn, hazard lights, indicators, electric start, ignition lights, neutral light etc etc all on at one time. Also, they get too toasty after a little while so won’t be at max either.
OTOH, have you thought about rechargeable heated clothing?. My sister had horses and regularly wore rechargeable heated coat and gloves. They lasted all day and got too hot so were never on max.

Martin

 

[Sidecar Bob]

I think I would too.

Re the "voltage monitor", I have voltmeters on both of my bikes (that's the summer one one in my avatar pic). The one on the winter bike is in the fairing and I used to turn things off as it dropped, starting with the handlebar heaters and stereo and if it didn't rise after that the sidecar headlight. A few years ago I was troubleshooting something else and noticed that the meter in the fairing read something like 3V lower than the multimeter I had connected directly to the battery with the engine not running and everything turned on.
At first I thought the fairing meter was failing but I connected the multimeter across it and they matched so the voltage was definitely lower at the fairing AND depending on how many of those loads I turned on the difference between the the battery and the fairing increased .
So I checked the voltage drops across the wiring and figured out that the bulk of the difference was in the negative circuit, which made sense since it was carrying the return current from everything. I made some improvements in the ground circuit wiring and fairing meter now reads closer to the battery's actual voltage with everything on.
One of these days I'd like to pull the harness apart and replace the main positive wire and the ground wires with heavier wire but that is a huge job and there's always something more interesting to do so for now I don't worry s long as the fairing voltmeter reads above 12V with everything on.
.
BTW: I don't consider it cold weather biking unless it is at least a few degrees below freezing (below -20c is hard cold and below -30 I stay home if I can (easier since I retired). Most of my winter biking has been within an hour of home and on a sidecar outfit so what I'm wearing at the start is usually OK for the whole trip. And with the sidecar finding a place for anything I take off if it warms up isn't a problem.