concor

Is it possible to charge the car battery through the lighter? Thanks.

FredR

I have a feeling that circuit is isolated until the key is in the first position. I do not think there are any diodes in that circuit so logic suggests it is possible providing the applied charge does not exceed the fuse rating which may be chunky given what it is used for. Not so sure it would be such a good idea though even if it is possible. It will be interesting to see what others think.

So, better question - why would you want to do this? It is easy enough to remove the 928 battery and/or disconnect the terminals which is what I would always recommend a 928 owner to do then nothing to fry if something is not how it should be electrically speaking.

Presumably you have access to a charger with a socket fitting but surely it also has a pair of crocodile clamps?

Regards

Fred

tmpusfugit

The lighter circuit can be used to trickle charge the car...meaning charging at a very low rate. I don't think it a good idea but it can be done. Of the 3 928's I have owned all 3 of them had lighters whose wiring had be changed about by the addition of car phones, large amplifiers, aftermarket alarm systems and the like. Meaning your lighter circuit may not be what it was originally, the original wire is quite light in gauge, and the fuse is sized appropriate for its gauge, no more. That alone will control the absolute top end limit of the charge rate, too much current and you will blow the fuse, not enough and it may take many hours to top off the battery.

.... so using it may or may not require other steps to use it. Personally I charge my battery at the battery terminals themselves. That would be my choice for both trickle chargers as well as higher powered chargers. Doing that eliminates a number of possible problems inferred above.

jpitman2

For ease of access I have an off-road style charge socket - like a cigar lighter, but with a positive connection centre point - mounted under the rear license plate. Its connected direct to the battery poles via a small fuse. This way I can disconnect the battery to work on electrical items, but leave the charger connected. I use a 1.6A trickle charger - last battery made 7 years.
jp 83 Euro S AT 55k

FredR

JP,

Not in Riyadh I suspect?

Regards

fred

upstate bob

Why not use the terminal post at the right front fender in the engine compartment? I keep a battery minder on mine when parked.

dr bob

Certain years have been reported with lighter sockets that are active when the key is off. Most (including mine) have that circuit connected through the X bus relay, and therefore only active when the key is in the "engine run" position. Your charger will only be effective when the socket is connected to the battery. Easy way to check is to plug something into the lighter socket with the key removed. Does your test item work? If so, you can plug a maintainer into that socket and it will do its job. If the socket doesn't work with key off, do as the others suggest and connect at either the jump-start post in front or directly to the battery terminals in the rear.


Many of us have installed permanent connections for a charger. I have one in front, wired to the jump post and the adjacent ground point on the fender wall. I have one in the rear, connected directly to the battery posts, so I can lift the ground strap and isolate the battery from the chassis, yet still charge the battery in the well. Both connections have fuses in their positive wiring.

j.kenzie@sbcglobal.net

I am sorry, but the access to the battery in the 928 is a PITA. You have to pull the spare tire, tool kit, jack, and then you can open the battery compartment and see the battery. I use the jump post for battery charging.
Good luck,
Dave

Alan

There is no stock wiring diagram for any year that shows an always connected lighter socket. Some have reported thay have one, I'm convinced in these cases that somebody has modified it (some owners think otherwise)...

In any case there should not be a permanent connection there on a factory configured vehicle.

If you like - test to see if it works with the key off as Dr Bob suggested - I think you will find it doesn't. Plenty of other ways to connect to the battery that are better..

Alan

jpitman2

Fred,
No, not in Riyadh, back home in Oz. First Riyadh battery was a German Varta, fully imported - died in 3 months with a dead cell. Took it back - No, no warranty on those Siddiq, but these joint venture locally made units have a 12 month warranty, I think you need one of them. Thats the one that lasted 7 years, most of it here in Oz.
jp 83 Euro S AT 55k

dr bob

Tangents to a bigger question. Is your battery vented outside the battery well? Charging the battery generates oxygen and hydrogen, and at serious rates will also cause acid vapors to carry over through the vent system. The first two together make a nasty boom if there's enough and a spark. The second is a longer-term issue with corrosion in the box.

Hence the factory recommendation that the battery should be removed from the car for charging, although that's probably in consideration for the possible spark in the explosive environment there, and the spark as the charger is disconnected. I have the vent hose connected to discharge outside the well, so I don't worry much about vapors with my little 1.5A maintainer connected. Plus I'm probably charging harder than that for the first miles after an engine start anyway.

j.kenzie@sbcglobal.net

Thanks Dr. Bob. I am pretty sure I installed vent tubing, but I will double check. BTW I know hydrogen can be generated during charging, but I didn't know oxygen was.
Dave

Mrmerlin

to charge the battery connect new leads to both terminals and leave the lead in the hatch area ,
disconnect the hatch connector so the lights wont come on when the hatch is open,
charge the battery that way,
OR open the hood and connect a charger to the hot post and the crossbar bolt

Alan

I think there is very little doubt about that!

Alan

concor

Thanks a lot guys! Great to hear all these options, suggestions and explanations. And even someone who is charging on 1.5 amps.

I will have to check if my lighter is connected. My 6 year old battery is rather dead so I removed it to carefully add water. It's on a slow charger now to get it back to life.