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Installing a USB/cigarette lighter charge socket


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Hi All

I'm hoping to get your learned advice on installing a USB charger socket panel in my car? I've trawled through all the previous posts on this subject so have researched it as much as I can but being mainly electrically illiterate I've still got a few open questions.

I've bought this charge socket panel https://www.amazon.co.uk/SONRU-Cigarette-Voltmeter-Independent-Motorcycle/dp/B07GRKB7SC/ref=pd_rhf_ee_p_img_5?_encoding=UTF8&psc=1&refRID=JKPHCYET06FHNG1CFVBQ

I've fabricated a bracket to hold it at the front of the transmission tunnel under the dash. Regarding the wiring side of it:

1) it has an in-built on/off switch and inline 10A fuse, so I'm intending to connect the positive wire directly to the battery. I understand this to be quite sensible and safe, is there any reason I shouldn't?

2) previous posts suggest either wiring the negative directly to the battery as well, or to an earth point on the car. Is either of these options better or worse? Where is the closest earth point under the dash? I think someone mentioned the windscreen wiper motor is an earth point, can I just attach it to any bolt on the wiper motor?

3) I'll need to extend the positive wire to get it to reach the battery, what wire do I need to buy to be safe? Halfords has a range of 5Amp, 17Amp, 27Amp wires, do I just buy the 17Amp wire as this will be enough to cover the 10A inline fuse? (the wires on the unit I've bought are 18AWG 600V).

4) The two options to run the cable to the battery seem to be to thread it through the existing wiring loom hole in the tunnel or drill a hole through the bulkhead. Is this just a matter of preference and visibility of wires etc? Is the only risk of drilling a hole through the bulkhead creating a water leak path?

Thanks in advance for any help.


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Brief answers:

1. Yes directly to the battery, but locate the in-line fuseholder as close to the battery as possible (not at the socket end).

2. Negative direct to the battery is simplest, and avoids possibly disturbing other earths (there are quite a few at the wiper motor)

3. 17A wire is fine

4. matter of preference/ease. If you drill through the bulkhead be sure to fit a rubber grommet to protect the cables passing through the panel.

Should be a straightforward job electrically.

Have fun! *wink*

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As Ian and John say.

You've got 2 USB sockets there each offering 2.1 A. That's smart for the future and I wouldn't recommend anyone to go for less.

There has been a problem with electrical noise from that type of USB device affecting an intercom. If you're considering that then check asap.


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  • 2 weeks later...

I was messaged by Rob Ismay asking for some info on how I mounted my charge socket, so I thought I would post some instructions, images and links to the items I bought in case its helpful to anyone else as well. I can't seem to get the orientation rights on some of the images so you'll have to turn your heads for some of them *rotate*

Front of charge socket, with integrate on/off switch to isolate it when parked up, dual 5V 4.2A USB sockets and cigarette lighter for plugging in the trickle charger in the garage.



I removed the ring connectors and the in-line 10A fuse from the harness and added male bullet connectors so I can unplug or replace the unit in future if required.



I spent some time placing the charge unit in different places under the dash before deciding it best fit as far forward on the transmission tunnel, next to the main harness and up against the heater cowling. In order to house the charge unit and give it a bit of dust protection I bought a plastic box (link below) of a suitable size from Homebase. 3_3.thumb.jpg.31a8b070207922bc9830e233607bacca.jpg

I cut the back off the box using a rotary tool cutting disc (although a hacksaw would also work) so I could stick it to the front face with double sided tape to reinforce the mounting surface and fill the gap caused by the facia of the charge unit being slight too large to sit neatly between the upper and lower lips of the box. I marked out the socket locations on the plastic box and using a drill and rotary tool sanding disc (although a file would also do the job) I cut out holes for the sockets and test fitted the charge unit in it's new housing.

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Cutting the housing to size - Using the depth of the sockets as a guide I cut down the depth of the housing (removing the charge unit first), then offered it up to the tunnel under the dash. After some marking and cutting, and more marking and cutting, the housing now fitted snuggly into its intended location. I drilled a hole either side of the housing to take a bungee cord, then masking off the outside of the housing I sprayed a few thin coats of black paint on the inside of the housing. I bought some 25cm bungee cords from homebase (link below). I had to unwind the thick metal wire wrapped around the doubled-over end of the bungee cord, which was holding it into the bungee hook, so I could thread it through the holes I drilled into either side of the housing. Once I did this I reinserted the bungee cord into the hook and re-wrapped the wire around the bungee cord to restore it to its original condition.



Then I installed the charge unit into the finished housing.

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Installing the wiring (all electrical items purchased from Halfords and links below) - from inside the car, using a long screwdriver I pulled the rubber gasket around the main harness located at the front of the transmission tunnel to one side so I could thread the cables through. I kept threading them until they eventually appeared from around the transmission under the car, then threaded them up into the engine bay to the battery. Using the in-line fuse I cut off earlier I connected it to the end of the positive cable using a butt connector. I also added a ring connector to the negative cable. Ensuring enough slack in the positive cable to be able to replace the inline fuse if required I cable tied the cables to the existing cables so they ran neatly to/from the transmission tunnel. Giving myself some extra cable length in the cabin for any future requirements I cut the cables and put female bullet connectors on them.

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Finally I plugged the charge unit into the cables, positioned the unit at the front of the tunnel and using the hooks on the bungee cord clipped it to the tunnel top cover.

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I've since gone back and added some rubber gasket to the end of the housing next to the main harness just to make sure there's no rubbing. There's some things I'd do differently a second time, like removing less material from the housing for the main harness clearance, and making a cardboard template before cutting the top of the housing to make it more accurate, but I'm fairly happy with the results and hope it gives some guidance or inspiration for anyone tackling a similar project.





USB/lighter charge socket http://https://www.amazon.co.uk/SONRU-Cigarette-Voltmeter-Independent-Motorcycle/dp/B07GRKB7SC/ref=pd_rhf_ee_p_img_5?_encoding=UTF8&psc=1&refRID=JKPHCYET06FHNG1CFVBQ

Plastic box https://www.homebase.co.uk/tactix-a6-storage-box-with-lid_p375010

Bungee cords https://www.homebase.co.uk/master-lock-mini-bungee-25cm-pack-of-4_p105333

Black 17amp cable https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-17-amp-cable-black-hef732

Red 17amp cable https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-17-amp-cable-red-hef731

Bullet connectors (male) https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-bullet-connectors-hef503-15-amp-male (female) https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-bullet-connectors-hef502-15-amp-female

Ring connectors https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-ring-connectors-30-amp-insulated

Butt connectors https://www.halfords.com/workshop-tools/garage-equipment/fuses-electricals-fixings/halfords-butt-connectors-hef522-15-amp

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Thank you for your detailed instructions. It is very helpful.

I was particularly interested to learn how you mounted the charging point as I too wanted to find a way to have the USB charging facility without making it a permanent fitting. 

Much appreciated.  

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  • 1 year later...

I've recently decided Id like to do this, and currently have no phone or iPod power supply and it would be useful. This looksa neat solution.  I have a FIA cut off key and would like to be able to disconnect the new power plug along with the rest of the car.  Is it a simple case of taking cable from the back of the new plug box to either of the big terminals on the FIA switch with a ring terminal, putting an inline fuse somehwere on the positive line?  

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Well the unit arrived, looks great, seems to work. As I want it for the weekend I’m not bothering with a box for now, it’s just cable tied to the tunnel bag mesh. 

However, I’m having trouble wiring it to the FIA key in such a way that it works! With the key off, I used the multimeter to find what I thought was the battery feed into the switch - Black probe on the steering column for earth, red on the battery feed going ~12v. So I put the red, fused cable from the new unit on this side, and the black earth on the other side of the FIA switch. The unit powdered up when the FIA key was off, but went off when the key and ignition was on.

I think I’ve just worked out why while typing this - it’s not earthed correctly. When the FIA key is off, it’s taking positive from the main battery feed, and earthing though the return. Turn it on, and it’s got two positive feeds so doesn’t work. I need to send the black cable from the new unit to an earth, probably the one on the wiper motor would be most convenient. 



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That’s better, now earthed one of the FIA switch mounts, and it works! Woo hoo. Only cable tied to the mesh, but probably secure enough but does look a bit Heath Robinson if looking carefully. Will revisit if when a bit more time over winter. 

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  • 1 year later...

Taking inspiration from David's original post, I've just installed similar although have fixed it into the fuse box cover and made use of the existing 12v supply to the original cigarette lighter, so avoiding having to make new connections to the battery.  The cigarette lighter is now also switched.



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