If like me you could possibly have the need to keep your car/van battery in a good state of charge, but do not want to go to all the trouble of fiddling about inside the engine compartment, then you can trickle charge your battery and keep your hands clean.
Inside your car there is something the mechanics use to diagnose faults when the fault light is illuminated. That something is called the OBDII socket and your car’s hand book will indicate where your particular one is situated. The OBD socket is permenately live unlike most 12v sockets/cigarette lighter sockets that require the ignition to be on.
If you have soldering skills or know someone who has, then an easily available OBD plug is available that can be soldered to your choice of trickle charger. Pin 4 is the ground connection and pin 16 is the permanent positive connection.
I have just taken a swift look on e-bay and I found a plug for £2.76 delivered.
I started building my own radio transmitters at school. The amateur radio exam contains a lot of electrical (& thus also physics) knowledge to pass. I have no issues with working on most electrical items, but personally I would not do that for myself or anyone else as I would worry about the charge handling of the OBD wiring. Also I belive some of these OBD points time out, so are not live all the time.
Just because something can be done, does not mean it should be done. Personally I would take a line off something like the side lights fuse to the cigarette lighter.
Both of those will require some kind of cabling identification, where as with the OBD socket, it’s a straight forward job. Oh yes, and pin 16 is permenately live so that a diagnostic reader can function independently of the ignition circuit. I’ve used OBD for various take-offs since they have been commonly fitted.
I suspect that the wiring to power a piece of diagnostic equipment is not designed to carry the current from a battery charger. Also you do not know what equipment is attached to this wire, it would only take a diode or zener in the circuit to thwart your ambitions.(a diode would allow current to flow out of the socket but not into the socket from a charger)
There is not a diode and the cabling is rated at 10amps, where a trickle charger is typically 1 amp with a maximum surge current of 2amp. I have been successfully using this socket since 2005 and so have several of my friends without incident. It is also commonly used by UK mechanics to maintain a supply to the car’s system whilst changing a failing battery without loosing saved on-board data etc.
It wasn’t clear that this was an old idea you had been doing for over 16 years, I thought it was something you were going to try.
Personally I can’t see the problem with opening the bonnet as opposed to a door. If you have the solder skills to do this why not fit a 12v socket (with a cover) or any polarised socket with an in line fuse in the radiator/bumper area so you can access it without opening the car at all? It would be easier to access than a OBDII socket which is usually situated under the dash and not particularly easy to get at.
My wife has no problems with the OBD location and she absolutely hates lifting the bonnet with all the steel work in her spine. Our cars are parked at the exposed front of our house and the chill factor for cars left for perhaps 6 or 7 days without being moved, will produce v poor starting performance form a battery heading towards the end of it’s life that would be otherwise fine in a more battery friendly environment. Her Suzuki is now almost 7yrs old (from new) with the existing battery, so as a precaution, a float charge is connect simply to ensure a good start when she does decide to drive somewhere. The Battery in my Pathfinder is now approaching 6 yrs from new, so again, the float charge is simply as a precaution. I cannot see the point of fitting an in-car live socket when the OBD already exists that has a fuse-protected continuously live pair.
