Forum

[NicoV]

I just installed handlebar warmers working at 12V, and pulling between 1,5 and 2,5 amps. I connected them to the battery to test them. I doubt this is a correct place to connect them to. I wouldn't be able to see on the amp meter the extra current they are causing. What is the most correct place to connect them ?

[Ian Martin]

I have always connected any heated grips I have installed to the live feed for the brake light switch, using an in line fuse to protect the rest of the wiring should a should a short develop in the grips. The live wire to the front brake light switch is already at the handlebars and more importantly it is switched off when the ignition is off meaning you will not walk away from the bike inadvertently leaving the grips on leading to a flat battery. It is also good practice to run an earth wire back to an earthing point on frame near the battery rather than relying on earthing through the steering head bearings.
Ian

[NicoV]

Ian Martin, very good idea, but I wonder a little if that line can stand 2,5 amps of current.

[papasmurf]

Amps Calculator for 12 volts systems here. Just scroll down the page:-

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

[PeteF]

You could always put a relay in.
A lot of heated grips have a battery saving mode whereby they switch off if the voltage goes down.

[papasmurf]

Is there anything wrong with reading the fitting instructions?

[jefrs]

The wiring on a bike looks thin but that's all it needs. The thinnest automotive wire is generally 5A, from the look (diameter) of the wiring on my bike it is 15A throughout apart from thicker stuff on the starter. The fuse on the Aux circuit (brake) is 10A(?) so the wiring will carry more than that. You don't really need an extra fuse but if you do add one it has to be rated at less than the fuse on the brake lamp circuit it is running from (or you would lose the brake light).

[papasmurf]

jefrs as far as I am aware all handlebar grip heating systems already come with an inline fuse. (Personally I never fit any electrical add on without it having a fuse.)

[jefrs]

Without knowing the model (Nico's '99 Bullet?), and its wiring, it is difficult to specify fusing. The heaters need to be drawn from a fused supply, probably 10A, so any in-line fuse should be less than that. Whether or not to include an in-line fuse depends on what it is, how much it draws and how likely it is to go wrong. I did not add an in-line fuse for the extra horns because the horn circuit is already fused, nor an extra relay because the wiring is well up to the job. The heaters draw about as much as the indicators, or a horn. The indicators only have a relay because they flash. Here I'd use any supplied pre-wired in-line fuse, but do check the rating is 5A or less, but not add an extra relay.

[papasmurf]

Jefrs it really is not difficult to specify fusing or wiring, it is very basic calculations for which I provided a link.

That is why it just took a few seconds before I did the wiring when I fitted a sidecar to a CX500 Custom that one of the fuses needed to be a higher amperage. I also fitted a flasher unit off of a Land Rover to handle the extra load when towing a trailor.