Extra power source

darkember · Post by **darkember** » Tue Mar 10, 2015 5:48 pm

Looking to install a USB port for my phone and a 12volt source for a sat nav. I have heard that running it from the rear light is a good source. Could someone point me to that thread. Also what size fuse should I be thinking of in terms of amps??

lloydie · Post by **lloydie** » Tue Mar 10, 2015 6:12 pm

take the live from the rear brake light switch and earth to rear coil mount .
fuse im not to sure on

darkember · Post by **darkember** » Tue Mar 10, 2015 6:25 pm

lloydie wrote:take the live from the rear brake light switch and earth to rear coil mount .
fuse im not to sure on

Why the brake light switch and not a constant source eg the rear light?? Also where is this switch found??

agentpineapple · Post by **agentpineapple** » Tue Mar 10, 2015 6:32 pm

I've still got to fit mine, i'm putting up front, taking power from the headlight, as I always have the headlight on....

lloydie · Post by **lloydie** » Tue Mar 10, 2015 7:10 pm

darkember wrote:
lloydie wrote:take the live from the rear brake light switch and earth to rear coil mount .
fuse im not to sure on
Why the brake light switch and not a constant source eg the rear light?? Also where is this switch found??

Follow the rear brake peddle and you will see some wires to the light switch then follow the wires up to the loom and you will find its plug (green is earth and leave it alone)
The other colour is the live , slice into it on the looms side as this is a constant live when the ignition is turned on .

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darkember · Post by **darkember** » Wed Mar 11, 2015 7:08 pm

lloydie wrote:
darkember wrote:
lloydie wrote:take the live from the rear brake light switch and earth to rear coil mount .
fuse im not to sure on
Why the brake light switch and not a constant source eg the rear light?? Also where is this switch found??

Follow the rear brake peddle and you will see some wires to the light switch then follow the wires up to the loom and you will find its plug (green is earth and leave it alone)
The other colour is the live , slice into it on the looms side as this is a constant live when the ignition is turned on .

Ok the above is all well and good. However, I would prefer my device to switch on when I want to switch it on. I could run a switch from the brake switch power source but that is too much of a faff. Could I use the power source from the side light in the front fairing that would then be switchable with the light switch.

lloydie · Post by **lloydie** » Wed Mar 11, 2015 7:16 pm

Yes

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tony.mon · Post by **tony.mon** » Wed Mar 11, 2015 8:37 pm

I'd have thought that it's always best to run a new set of leads from battery, via a relay. Take the relay switched side from one of the sources already mentioned, and fuse the supply side to the relay (the switched side will already be fused, of course).

But why not run a waterproof cigarette lighter socket and simply use a little plug-in double USB outlet? That way you have cig lighter type power output for stuff like a lead light or airbed pump, etc.
While you're there run a socket that's permanently live to connect a conditioning charger such as an Optimate.

-Job Sagoodun,
eletrickery fairy to the masses.

darkember · Post by **darkember** » Thu Mar 12, 2015 5:49 pm

I get your thinking Tony and have ordered a small relay. So basically doing it the other way is making a bodge job

. As for the fag socket yes too but will also need the USB at the same time. Will probably run both accessories from the one terminal off the relay.

Pete.L · Post by **Pete.L** » Fri Mar 13, 2015 8:43 am

As far as the fuse goes, You need to know what the wattage is of the individual items . If you are going to be using just the charger or the sat nav then just go by the highest powered one, if you want to plug both in, add their wattage (power together). Then you can apply ohms law V=IR or P(watts) =V(volts)I(current amps)
In this case we know the volts (12) and we know the wattage(P) so we can change the formula around to suit P/V = I as we need to know the current.

Fuses can only be bought at fixed values. So if you do your calculation and end up with a figure of 2.4378 amp, for example, you just have to choose the next available size up fuse. 3AMP in this case. This then leads you on to selecting your wire. As long as your wire spec is greater than the chosen fuse you will be fine. (you don't want your wires melting and causing a short before the fuse blows)

If the sat nav and charger are labels with their current instead of power (quite often in mA milli amperes) all you will have to do is choose a fuse

B

Both your items are pretty small, I wouldn't think they have a very large load so probably no need to go overboard and get massive cables, connectors and fuses. Keep it small , neat and tidy

Pete.l

StuartWags · Post by **StuartWags** » Fri Mar 13, 2015 5:02 pm

i have a auxillary power point (cigar lighter) off the battery and an adapter for usb

darkember · Post by **darkember** » Fri Mar 13, 2015 8:13 pm

Pete.L wrote:As far as the fuse goes, You need to know what the wattage is of the individual items . If you are going to be using just the charger or the sat nav then just go by the highest powered one, if you want to plug both in, add their wattage (power together). Then you can apply ohms law V=IR or P(watts) =V(volts)I(current amps)
In this case we know the volts (12) and we know the wattage(P) so we can change the formula around to suit P/V = I as we need to know the current.

Fuses can only be bought at fixed values. So if you do your calculation and end up with a figure of 2.4378 amp, for example, you just have to choose the next available size up fuse. 3AMP in this case. This then leads you on to selecting your wire. As long as your wire spec is greater than the chosen fuse you will be fine. (you don't want your wires melting and causing a short before the fuse blows)

If the sat nav and charger are labels with their current instead of power (quite often in mA milli amperes) all you will have to do is choose a fuse
B Both your items are pretty small, I wouldn't think they have a very large load so probably no need to go overboard and get massive cables, connectors and fuses. Keep it small , neat and tidy

Pete.l

Cool pete thanks for the heads up. Basically I will be running the Power socket and the USB on 2 separate 2.5 mm wires from the switched side of the relay. The switched power will be supplied from the lighting circuit which is already fused again on 2.5mm wire. The accessories are both 1000ma therefore 1 amp each. I know 2.5 is a little heavy for this application but I have a perfect bit of 3 core 2.5 that keeps it all nice and tidy.

darkember · Post by **darkember** » Fri Mar 13, 2015 8:14 pm

StuartWags wrote:i have a auxillary power point (cigar lighter) off the battery and an adapter for usb

All good but what if you want to charge your phone and use the satnav at the same time

tony.mon · Post by **tony.mon** » Fri Mar 13, 2015 10:39 pm

darkember wrote:
StuartWags wrote:i have a auxillary power point (cigar lighter) off the battery and an adapter for usb
All good but what if you want to charge your phone and use the satnav at the same time

Charge the phone and use the satnav facility on the phone.

Why take two bottles into the shower?

bazza696 · Post by **bazza696** » Sat Mar 14, 2015 7:45 am

I bought a swithed relay kit forom eastern beaver, and run the switched wire to the side light so I can switch the power on or off if desired.

The eastern beaver kit comes with 4 fused power take offs, so you can run a DJ booth from it like Tony on our firestorm weekends.

VTR1000.ORG

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