The EX0.2 and KEIS vests are both made using a conductive material rather than a mesh of wires. The material method means no chance of a wire kinking or burning through. EXO.2 make a big point of having been tested by the Royal Marines. This impresses me. The no-wire technology is the reason that I settled for one. Looking carefully at the ads you'll notice that the KEIS heats less of the body than the more expensive EX0.2 does. The KEIS can easily be run at level 3 out of 5 if worn as advised over a thin layer under a tight layer. The EDZ pertex shirt is probably an ideal over elec vest layer. Linzi.

I'll have a bash at this although I should point out I am definately not an electrical engineer, but as I also use heated clothing I gave myself a crash course in all this stuff.

Your bike generates power from the Alternator, in your case 225W. This 225W has to do two things, charge the battery and power all of your electrical equipment. At it's most basic the electrical equipment on a bike consists of bulbs and your horn, so calculating how much power your bike needs is simply a matter of totaling everything up. I don't know what bike you have so I will use my Trans Alp as an example, all of the bulbs on my bike (and the wattage of them is listed below):

Headlight (60 watts when full beam is on)
Sidelight (5W)
License plate light (5W)
Rearlight (5W, 21W when braking)
Turn signals (21W * 2)
Instrument lights (1.7W * 3)
Turn signal warning light (3.4W)
High beam indicator (1.7W)
Neutral indicator (3.4W)

Now obviously I am not going to have all of the above lights lit up at once, but we can work out a realistic max (Full beam, indicating and braking) of 60 + 5 + 5 + 21 + 42 + 5.1 + 3.4 + 1.7 giving me a total of 143.2W of power required for the lights. I don't know the exact power requirements of the horn, but I think it's roughly 35W.

As for keeping the battery topped up with power, the best information that I can come up with is that on a normal charge the battery requires 1.2 Amps for 5 to 10 hours. Obviously a battery is not fully discharged after starting, but I will use the 1.2 Amps as a guide, and Ohms Law lets me calculate that 1.2 Amps in a 12 Volt system works out as 14.4 Watts.

I know that my Trans Alp puts out 368W at 5000rpm so even at the absolute max (full beam, indicating and braking while blasting the horn) I would only be using 193 of the available watts, leaving me with 175 available for extra's.

My heated jacket uses 77W, and a pair of heated grips would use 44W which still would leave me with some of the 175 spare watts available.

It's worth pointing out that switching from traditional bulbs for things like indicators that use 21 watts on my bike to LED lights that require roughly 5 watts would drastically reduce the amount of power your bikes electrics would require, leaving more available for things such as heated clothing.

Also on an older bike don't forget that there will/can be power losses within the loom due to corossion in connectors. This means you can have less Watts to use than leave the alternator for duty. Not all of them will make it to the battle front. Linzi.

No as far as I know Chris if you use loads of electrical items on a bike you won't damage the alternator, you'll just have all the items getting too little electricity. That will be a dull headlight beam and perhaps dimming if you use your horn. On an older bike you can also have losses along the loom due to high resistance in the wires and especially the corroded connectors. Linzi.

I think Aerostich make a Fleece electric vest? Kanetsu?

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Patrick passed Dec 2018. RIP Patrick!

Not sure of the brand but BIKE recently had an article on a heated vest. The jacket could be powered from the bike or with an optional battery pack.

It looked light and windproof and was about £80. It would solve the bulky issue and give you the freedom to keep the warmth going even off the bike. On its lowest setting it could run for 6 hours just of the battery pack. Could be a godsend if you break down.

The jacket didnt use wires so I guess it would be pretty durable.

I have my eye on one but need to try and make my own with the kit first to keep costs down.

This is the one I use, and after riding in minus temperatures with it on and still feeling nice and warm, without having so many layers on that I feel like the michelin man, there is no way I would go back to doing without.

One other thing to keep in mind with the volts watts and amps situation. Amps is the measure of electrical resistance (hence why fuses are rated in amps). A Gerbing jacket draws 77W of power, which on a 12 volt system equates to 7 amps (amps = watts / volts) so make sure you connect it all up using wires and connectors that are rated for at least 7 amps.

I originaly connected my jacket up to a cigarette lighter style adaptor that was only rated at 5 amps, thinking "Oh it will be OK, it will just get a bit warm". This was a mistake, it did get a bit warm as it melted the adaptor which at it's worst could have caused a small electrical fire and damaged other more important bits and pieces. I am now awaiting delivery of an auxiliary fuse box from nippy normans so that I can run all my additional electrical equipment through that, I have also ordered the relay kit from the same page so that the fuse box is only live when the ignition is turned on.

Hi Chris,

All nicely covered above except no one seems to have pointed out that the 225W is the maximum output. Some bikes won't hit this until 4000 rpm. With so little spare power, I'd be careful how you run a 55W vest. On a trail where you are at walking pace and fifteen minutes before each stop, switch it off. Also, controllers use power, as well as the jacket the coil in a reostat is getting warm. Most seem small losses, but i've seen one that used a Scaletrix part that could have been used to toast bread as a sideline

For sake of completeness:

Volts = Amps x Ohms
Watts = Volts X Amps

If you don't know how much power (Watts) an item might use, get the Amp rating off the fuse and use the formula. Unless you have a big alternator you'll scare yourself unless you use a couple of fiddle factors. Assume the battery is only 11.8 volts and all fuses are over rated by about 2 amps and you'll be close but safe. Indicators, the horn, brake light and the starter motor can have their power use reduced to 10% of the fused value due to intermittant use. If you are short of the odd 5 W look for an LED tail lamp, they use next to nothing. LED indicators simply move the load into a resistor block, so you only gain the lifetime, not the power use.

Andy

You know, that makes sense now you mention it, will keep that in mind for my future calculations.

Many thanks for all your explanations and ideas.

... 225W is the maximum output. Some bikes won't hit this until 4000 rpm ....

Yes, I was wondering about that. It seemed an optimal output figure that would only deliver out on a steady highway, not in town or on slow terrain (tho' negotiating the latter can warm you up).

Does an alternator running at near max also reduce the bhp noticeably, or is this too marginal to notice on anything other than a 125 @ 4000m.

It's a shame to see all that free engine heat blowing away too. I tried it once with hoses from behind an oil cooler running up my sleeves but there must be better ways, especially with water-cooled bikes. I imagine some Siberian motard must have thought of this.

Ch

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Morocco Overland 4 (2025) • Trans Morocco Trail

If you use 500W you will reduce your bikes power with 0.7-0.9 hp.

I thought of this a while back and one solution was to wrap a copper/bailing wire line around Exhaust/Coolant Hoses and wind that up to the handlebars.

The issue is how does one control the temperature output.

I do have another solution in the works...wireless heated garments.

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edde
93 BMW K75s
www.motoedde.com

The watts your electrical equipment use are the same your engine HP could be expressed in. Even if you have 10% efficiency, you've a lot of KW in that engine.

About 70 years ago some very unpleasant chaps organised the worlds most unpopular road trip taking in such locations as near Moscow and Stalingrad in January. Their BMW's and Zundapps although only available in limited colours ( Grey or Sand), did have some interesting optional extras. They had what looked like vacuum cleaner hoses feeding from behind the cylinders into foot and hand guards. These must have done something useful as most military types I've known would soon "loose" anything that wasn't and you do see the heaters on photographs. I've wondered what could be achived with a bit of hose, some 5-litre plastic containers and lots of duct tape.

Even better, I've seen pictures of (I think) a Yam with a hot water line tapped off the radiator. I'm not planning on going watercooled unless there is also a heat exchanger and you can use the water to make tea

Andy

... I've wondered what could be achived with a bit of hose, some 5-litre plastic containers and lots of duct tape.

Now you're talking! It's sort of what I have in mind, along with a board across the front of the engine as you do with radiators in the cold. It's something you could almost bodge by the roadside out of rubbish if it gets desperately cold and you have a long way to go.

Any pix of the Stalingrad posse's rides?

Ch

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Morocco Overland 4 (2025) • Trans Morocco Trail

I remember reading something years ago in the BMF magazine,Motorcycle Rider or whatever it's called,about an NTV 600 that had it's coolant running up a load of pipework and through the handlebars.I cannot remember much detail but I suppose that you would want a tap so that you could turn the heat up/down/off if you wanted.

I have a homemade heated vest,for winter use I wouldn't be without it.