Battery completely dead

[Fatbloke]

Hi all

The wife's Boxster is in our garage and the battery has gone completely dead in about 3 weeks. It wouldn't start a few weeks ago but still had some charge in it so I popped the bonnet (hood) and fully charged the battery.

It has been sitting for about 3 weeks so I went to start it to get some oil round the engine. Unfortunately the battery is completely dead, not even the interior light or any dash lights come on. The battery is a known good one out of another vehicle that I put into it in the summer as the original battery had failed. It is a slightly more powerful battery than the original.

I tried to get enough charge into it to pop the bonnet so I could get in to charge the battery properly with a small trickle charger plugged into the cigarette lighter socket but it has made no difference. It is still completely dead.

Is there a reason the battery won't charge via the cigarette lighter (2004 2.7)??? Possibly a fuse gone somewhere that cuts all power???

I did read that there is a small cable for opening the bonnet in behind the wheel arch but wanted to avoid trying to locate that.

How can I get enough charge in so I can open the bonnet or is there another way???

Cheers

Dave

[Steve Tinker]

Please, please use the search function - there is a myriad of questions and answers exactly the same as yours from the last xxxx years.......

[Fatbloke]

I have searched and it seems I can try getting enough charge in to open the bonnet via the fuse box. I will try that tomorrow.

Is it normal for the battery to drain completely in 3 weeks or is there a problem???

Cheers

Dave

[jhiggi83]

Originally Posted by Fatbloke

I have searched and it seems I can try getting enough charge in to open the bonnet via the fuse box. I will try that tomorrow.

Is it normal for the battery to drain completely in 3 weeks or is there a problem???

Cheers

Dave

It sound like something is causing a load on your battery when its not running. That would explain why the battery is completely dead since the car was not able to charge it. I don't know what it could actually be causing the drain. Do you have any aftermarket stuff installed wired to the battery. Its impossible to find exactly what you are looking for on the search function. Ive tried many times with different topics

[clickman]

Originally Posted by jhiggi83

Its impossible to find exactly what you are looking for on the search function. Ive tried many times with different topics

I've found it more effective to Google the issue including the term 986forum

[Jamesp]

If it is a 2004 there is a pull out in the fuse box that runs to the hood release, no charging needed, just a 12v source. Open the fuse box and look for the paper directions clipped to the fuse cover, it explains how to open the frunk with a 12v source.

[Fatbloke]

Thanks guys.

There is nothing aftermarket fitted that would drain the battery. The only thing different from standard are the 5w bulbs which are now led.

I read somewhere about a similar issue caused by a faulty starter or alternator but that was much more extreme, draining the battery in hours or a couple days. I haven't tried to start the car for about 3 weeks so I don't know when the battery was drained. It could have just been a few days. I will get it checked out once I get in to it and charge the battery.

Regards

Dave

[Fatbloke]

I managed to get into the bonnet via the fuse box.
Thanks for the input guys.
Next problem is to find out what's draining it.

[husker boxster]

How new / old is your 'good' battery. Maybe it was it's time and gave up the ghost?

[KRAM36]

When you lock the doors, the auto theft system kicks in. I have a little red light on the dash that blinks constantly until the car is unlocked.

[TripleTrophy]

When I purchased my (admittedly an) '06 the dealer said if I wasn't running it for more than a week put it on a trickle charger. They weren't kidding! My '11 Ducati Multistrada also eats batteries, seems to be problematic with newer vehicles that aren't run regularly.

I had issues last summer when the weather and events conspired against me, and I ended up replacing the battery. On the '05 and newer there is an extra plug just beside the passenger's feet for trickle charging, and I understand it bypasses the fuse box to try to avoid any charging problems.

[Fatbloke]

The battery is a few years old so may just have died but it was fine through the summer. I am trying to charge it now but the charger is only putting in 5v for some reason.
If the battery is discharged to basically zero, does that knacker it??

I am going to try my heavy duty charger on it tomorrow. The one on it just now is just a small charger.

I may need to buy a new battery, Bosch S5 100 or 110. Don't want to do that if it is going to discharge them until they die though.

Cheers

Dave

[TripleTrophy]

Just a thought, does your charger have the option of 6V and 12V output? 6V won't charge a 12V battery. Unfortunately I speak from experience...

If the battery is just dead, it should recharge. On my first car I left my headlights on when I was out on a Tuesday, and for some reason the car wouldn't start on Saturday. I boosted it, and ran the car another 6 years on that battery, never changing it. But, that was a long time ago with less electronics. If the cells have started to short out then it is probably shot. Some people claim around here the life expectancy of batteries in seasonal vehicles (aka toys) is three years, I usually get about 4.

[Fatbloke]

The charger does 2v, 6v and 12v. I made sure it was set correctly. I will try it on another known good battery to see if it still does the same. It may be knackered too although I have only used it a few times.

Big charger on the battery tomorrow to see if it charges it.

Dave

[Joe B]

Buy an AGM battery and disconnect the negative terminal (or put it on a trickle charger) if the car won't be driven for more than a week.
End of problem !

[Fatbloke]

Looks like the big charger is charging the battery. I will leave it on overnight on normal charge rate and see if it is fully charged tomorrow.

Is there any way I can check what's draining it?

[Joe B]

All Boxsters drain the battery more than most cars. Alarm system? I don't know, but it's normal. And just because your battery comes up to a full charge doesn't mean it will hold it, especially if it's been drawn all the way down before. Automotive starting batteries don't like being fully discharged. You need to take the battery into a shop or auto parts store and have them load test it.

[SoCalBlackbox]

My car is usually pretty good and has always started even after sitting for weeks. Last week I left the key in the ignition. Saturday I noticed the airbag light was on I opened the door and the courtesy lights didn't come on. The battery was DEAD so I charged it overnight at 2 amps and it seems to be OK. My question is does leaving the key in the ignition cause extra drain. I'm not going to do it again but I wonder if that was the cause.

[Steve Tinker]

^^^ YES ^^^

IIRC leaving the key in the ignition will flatten the battery in +/- 4 days..... ask me how I know!

[BOOTLEG]

I measured .27A flowing with key out and everything off. I think this is a lot and plan to track it down. Will post findings.