MODERN SATNAV IN A 6-VOLT BOX

My old satnav worked fine in the Box having wired up its cigarette lighter/USB port to the 6v battery.  But looking forward to our holiday in France with the club, on checking the old satnav it was clear that its maps were nowhere near up to date so a ‘new’ secondhand one was purchased from eBay.  What became very clear straightaway was that the new satnav wasn’t having any of the old electrical arrangement.  Clearly, the new cigarette lighter/USB port it came with needed a 12v source to be able to step down to the standard 5v input.  However, on further research I read that the later satnavs are more sensitive to their input and could be damaged if not fed an exact 5 volts and talking to club members revealed that the standard dynamo could deliver anywhere between 6 and 8 volts. Other club websites also warned about trying to wire up a satnav to a 6v battery.  However, I must say that everyone I asked in the club said that they had had no problems over the years but when I looked at their arrangement in-car it was clear that they were using old equipment all round.  So, to persevere with an upgrade, this is what I did:-

The objective was to fit a female USB port in the glove compartment that would deliver a guaranteed 5v output when wired into the car’s 6v battery and to do without the cigarette lighter arrangement.
Technically it should have been very simple. However, I couldn’t find a readymade unit that would do the job but I did find the bits and pieces needed for a DIY job in good A7 style.  The problems only existed in my lack of electronic skills and needing a more steady hand.

1.     Purchase a step-down Module that takes whatever voltage comes in and gives out a constant 5v.
        1.1.  Amazon: “ZK 5 Pcs 6-24V 24V 12V to 5V 3A USB Step Down Module DC-DC Converter” x5 for £5.59 +£4.99 delivery. (I’ll explain why I needed 5 later.)
2.     Purchase a suitable little box to put it in.
        2.1.  OnBuy.com: 4x “USB Stick Plastic Box Electronics Enclosure USB Flash Drive Housing Plastic Junction Box”. £8.23 + free delivery. (4 needed for trial-and-error fitting. See later.)
3.     Find the right wire for the job. Needs to be very fine but flexible.
4.     Connect up to the battery or ignition. (I decided to connect it to the battery on the red-switched side.) I used those blue electrical connectors in the glove compartment in case it didn’t work but obviously the unit could be wired directly to the battery/ignition and left in the glove compartment if you’re confident of your wiring and soldering.

This is what you get:                                                                   
 
 
 
  This is what you need:
 
 
  Construction:
Open the box with a small screwdriver and try to fit the module with the USB port in the rectangle hole.  Part of the mouth of the module should fit over the outside of the aperture in the box and the body of the module behind the aperture so that the module can’t be pushed in or pulled out when in use. In my case, the wall of the box was too thick so some careful sanding and trial-and-error fitting was required until the module slid down tightly over the mouth in the bottom tray and the top half of the box also pushed down over the module, snapping shut. (This is where the need for 4 boxes came in!) The next job is to determine which is the top and bottom as the slot isn’t central and neither is the body of the module.  What you want to achieve is the module sitting tightly in the slot and with its bottom on the floor of the tray.  Mine was a bit short so that’s where the little square rubber pad came in for it to sit on.  Once the ‘mock-up’ was achieved, I put a dob of Tippex on the bottom of the tray as a fixed point for the final assembly.

Having got the physicals right, all(!) that needs to be done is to wire up the module and organise the cables.  WARNING: Do not try to solder-in the wires. It might have been my lack of soldering skills but I blew two modules before I realised what was happening (this is where having 5 modules to play with came in!) So I twisted the wires tightly into place (this is where flexible wire was needed as, at first, I used some stiff, single strand wire which was easy to push through the tiny holes but it kept breaking) and used Araldite to fix them in place (having determined that Araldite isn’t a conductor). Slide on a suitable grommet to stop the wires from wobbling the module about in use, cut to length and fit the connectors or run the wires to the battery/ignition.  Now fit the whole unit together and use superglue to glue the two halves of the box together for extra rigidity.
 
 
 
 All over France, and subsequently, it has worked flawlessly and will now be a permanent addition to Frederica. However, I did take with me a belt-and-braces backup in the form of a modern Power Bank with 20,000 units of power and a multitude of cables and connectors which, I think, would have done me for the whole week away. I chose the “VRURC Portable Charger 20000mAh with Built in Fast Charging Cables, Power Bank PD 18W” through Amazon at only £21 + postage.

David Whetton DA7C