Need help -- battery issue

[JST]

So I went to charge the battery in the Porsche. Put a battery tender/charger on the battery--clamp to positive, clamp to chassis ground.

So far, so good.

Then, like an asshole, I closed the trunk.

The car went completely dead. I managed to get the trunk open with the emergency release, and I think what probably happened is that the trunk lid hit the positive cable and shorted everything out.

My question is: did I just blow a fuse? If so, any ideas which one? Or did I fry something electronic somewhere ($$$$$$)?

Right now, the car is totally dead--can't even remove the key.

[ZBB]

You likely blew a fuse. Check the fuses -- in the driver's footwell.

When I had my boxster, the fuse for the lighter socket would blow every few months, so I got used to changing it...

[JST]

Went through them. Can't find any obvious ones blown, though I did get a click after resetting the big relay and now I have a weak, intermittent passenger airbag light--no other power.

[Nick M3]

Does the car have a fusible link to the DME/main modules? Could have easily burned that out.

[JST]

Possibly? Where would that be--in the fuse box, or elsewhere?

[Terri Kennedy]

Then, like an asshole, I closed the trunk.

The car went completely dead. I managed to get the trunk open with the emergency release, and I think what probably happened is that the trunk lid hit the positive cable and shorted everything out.

My question is: did I just blow a fuse? If so, any ideas which one? Or did I fry something electronic somewhere ($$$$$$)?

If you shorted the charger cable, you should have melted wire on your charger cable. If you shorted the battery, the melted spot would be on your trunk lid. This assumes the battery had a reasonable charge - look at my last paragraph.

I don't know anything about Porsche wiring, but the first thing I would try would be disconnecting the battery for 10 minutes or so, then re-connecting it.

If the battery is in the trunk and the fuses are at the other end of the car (like BMWs), it is unlikely you blew any fuses because they are "downstream" of where you shorted out the battery.

You could also try charging the battery while it is disconnected, or trying jumper cables with the battery connected. You may have a battery that is so weak it no longer takes a charge, and the short from closing the trunk lid drained it completely. Did you put the trickle charger on it just to "top it up", or was it acting low / dead before?

[bren]

I don't know anything about boxster electronics, but if you left the charger pumping electricity while shorting the terminals :eek:

I have a co-worker with a vw who hooked jumper cables backwards between two cars and fried the main chassis computer.

So yeah, good luck.

[kognito]

Does the car have a fusible link to the DME/main modules? Could have easily burned that out.

This is what my first thought was also.

[kognito]

http://www.justanswer.com/porsche/7gqt5-porsche-cayenne-turbo-s-hello-reset-car.html

Porscheguru is online right now

[John V]

Battery tenders don't deliver that much current. If it had been a high ampere battery charger it probably would have delivered a pretty big spark. The battery was probably completely dead (and not recoverable, if it's been left flat this long) and you killed the battery tender when you shorted it to ground. Nothing should really have been damaged in the car's circuitry from shorting the positive to ground through the chassis.

Hook up another 12V source (like, a car battery) to the car and see if everything is OK. I'm guessing it is.

[JST]

Thanks, John. Put a multimeter on the battery this AM and it's showing 3.6 Volts, so it's clearly super dead. Will throw a new battery in and see what happens.

[John V]

And I stand corrected on the tender. Shorting the terminals together shouldn't kill it. Mine has a fuse in the hot side lead, but it appears to have internal current limiting.

[lip277]

And... For the Porsche - I use a cigarette lighter connection (http://www.amazon.com/Battery-Tender-Deltran-Cigarette-081-0069-5/dp/B003CJ927I)for the BatteryMinder I have. The cig outlet is always hot and I charge the Porsche (and 740iL as well) that way.

That way I don't mess with the battery itself (or the trunk/frunk lids and such).

Just a thought -

[John V]

I just use the bolt on adapter for the tender. No clip leads. Clip leads are evil.

[Alan]

So I went to charge the battery in the Porsche. Put a battery tender/charger on the battery--clamp to positive, clamp to chassis ground.

So far, so good.

Then, like an asshole, I closed the trunk.

The car went completely dead. I managed to get the trunk open with the emergency release, and I think what probably happened is that the trunk lid hit the positive cable and shorted everything out.

My question is: did I just blow a fuse? If so, any ideas which one? Or did I fry something electronic somewhere ($$$$$$)?

Right now, the car is totally dead--can't even remove the key.

Arrrgghh ... I hate when these things happen .... Fingers crossed it's just a battery needing to be replaced.

[JST]

Ok, new battery seems to have fixed the issue. Car fired right up.

Here's what I think happened--when I closed the frunk, the lid made contact with the clip on the positive terminal of the battery. I immediately unplugged the charger, but the short stayed in place as long as the lid was closed (it took me about 20 min to get the wheel off and get to the emergency release). This discharged the battery essentially completely.

What was throwing me off was that all the electrics in the car shut down instantly when I closed the trunk--that's what led me to think I blew a fuse. But as I think about it, what probably happened was that the short shunted all the electricity through the path of least resistance, so as soon as I closed the trunk the power going to the rest of the car dropped essentially to zero.

Anyway--thanks for the help. I won't do that again!

[lip277]

Good to hear.
And.. Yes... Mounting the terminal connector directly to the battery or using the cig lighter adapter (for the P & BMW) is the way to go.

I only use the alligator clips on my mower or old cars. And... I leave the hood open on those when the clips are on there.

:lol: I have 7 or 8 battery chargers on my cars/mower/boat/generators... Too many things. :eeps:

[John V]

No harm no foul. Glad it was easy. logically, it was not likely you hurt the car.