Flat Battery - why?

[vincematthews]

Came back from a couple of days away to find the battery totally flat.
The neighbour said the alarm had been going too - presumably because it mistook the flat battery for being interferred with.
Recharged the battery - took 16 hours but charged no problem - and refitted it and everthing inc the alarm/immob. works fine.
I checked the power draw for the battery fitted (and nothing apparently switched on except the security) with an ammeter in series and got a reading of 0.05 amps which seems ok to me.
Started the car and the alternator seems to be functioning ok too.

I can't see why the battery would totally discharge so quickly though? i.e. down to a reading of 0.15 volts.
I know there are theories on this but it no longer has the Porsche alarm system.
Could it possibly be that if the battery has no cover fitted, it can short circuit through damp sound proofing - see attached



This damage happened before I had the car . . . anybody else seen this.

 

[Copperman05]

When was the battery last replaced?

Edd

 

[vincematthews]

ORIGINAL: Copperman05

When was the battery last replaced?

Edd

Supposedly before the PO sold it to me about a month ago (there is what looks like a date sticker that says 08/10 on it) - I suppose it might never have been charged properly from new . . .

 

[Hilux]

Is the positive cable original?

Interesting marks (charring?) on the cover. If the foam got wet it could make a circuit.

Have you a plastic cover to go over the positive terminal?

 

[vincematthews]

ORIGINAL: Hilux

Is the positive cable original?

Interesting marks (charring?) on the cover. If the foam got wet it could make a circuit.

Have you a plastic cover to go over the positive terminal?

Appears to be.

Rather what I was thinking though a continuity test was negative at the moment.

I have now [8D]

 

[964RS]

Your battery is likely to have had a deep discharge [8|] [] Find a friendly forum member with a CTEK XS-7000 battery charger (or similar) which will recondition your battery. This may take a few hours on the charger - do in a well ventilated garage. Make sure the acid is topped up to the level with de-ionised water if it's not a sealed unit before charging.

Also, I don't see any copper grease on the terminals. Remove the leads (positive first) then coat the contact surfaces in copper grease (Copper Ease) before reconnecting. Remove the chassis end of the negative cable and coat that also. []

These steps are easy and cheap - before you go down the route of changing the battery and an alternator check etc. [8|]

 

[vincematthews]

ORIGINAL: 964RS
Your battery is likely to have had a deep discharge [8|] [] Find a friendly forum member with a CTEK XS-7000 battery charger (or similar) which will recondition your battery.

But why should it "deep discharge" [8D] in just a few days when it appears fairly new and seemed fine for the last month? Surely this would point to something wrong with the charging circuit?

I've got it charged now with a Gunson Multistage Gold charger which seems to be reasonably 'intelligent' - how is the XS-7000 different?

 

[tref]

Just so we don't forget the obvious, there isn't any chance you left a courtesy/glovebox/boot/side light on is there? That'll discharge a battery in a relatively short space of time, and is one the common reasons for a one-off flat battery.

Tref.

 

[Alpine]

ORIGINAL: Hilux

Is the positive cable original?

Interesting marks (charring?) on the cover. If the foam got wet it could make a circuit.

Have you a plastic cover to go over the positive terminal?

does the positive need a cover? My old Bosch battery had a cover over the + but my new one doesn't

 

[964RS]

ORIGINAL: vincematthews

ORIGINAL: 964RS
Your battery is likely to have had a deep discharge [8|] [] Find a friendly forum member with a CTEK XS-7000 battery charger (or similar) which will recondition your battery.

But why should it "deep discharge" [8D]  in just a few days when it appears fairly new and seemed fine for the last month? Surely this would point to something wrong with the charging circuit?

I've got it charged now with a Gunson Multistage Gold charger which seems to be reasonably 'intelligent' - how is the XS-7000 different?

You may not know the history of the battery or if it's been discharged previously.

I've managed to resurrect 'dead' batteries and batteries that don't hold their charge with my CTEK. The XS-7000 reconditions a battery that either suffers sulphation (unused/under-used batteries suffer from this) or acid stratification (fully discharged batteries suffer this).

A long shot, and a difficult one, is to replace the acid and recharge. Battery acid is difficult to get hold of although Porsche did sell it IIRC.

 

[vincematthews]

ORIGINAL: 964RS
You may not know the history of the battery or if it's been discharged previously.
I've managed to resurrect 'dead' batteries and batteries that don't hold their charge with my CTEK. The XS-7000 reconditions a battery that either suffers sulphation (unused/under-used batteries suffer from this) or acid stratification (fully discharged batteries suffer this).

Cheers for that - will look into it.

ORIGINAL: tref
Just so we don't forget the obvious, there isn't any chance you left a courtesy/glovebox/boot/side light on is there?

I don't think so - with a current draw of only 0.05A including the alarm system . . . ?
At that rate, my 68Ah battery should last 56 days . . . . theoretically []

 

[bertelli_1]

You said the alternator 'seems ok', what voltage is it putting out? Just take it down to your local tyre & exhaust place - most of them will do a free battery test.

 

[djaychela]

Charge the battery up again, and take it to a shop where they can run an alternator and battery capacity test. Removes a lot of unknowns in a couple of minutes. I've owned a lot of cars, and batteries can lose capacity, some in a short time if the battery has a fault; I've had some that have lasted years and years, others that have had new-looking ones which have died in short order; the capacity test is the quickest, simplest way to check it, but if that turns out OK then there's something else at play. I'd be very surprised if a wet foam cover conducted, but I've seen many a car with odd current draws, although you seem to have checked the right things so far. Disconnect the earth and leave the battery in the car for a couple of days and see what it does then...

 

[vincematthews]

Well I thought I'd double check the amps that the security system was using when activated and got a reading of 0.7A!!
Thought that can't be right and then noticed the interior light was on [8|].
It turns out Tref was right after all (some of the time [] ) in that sometimes the light switched off and sometimes it didn't. Apologies Tref.
Pulled the switch out of the door pillar and it seems to operate ok mechanically.
When I put it back (with the courtesy still light on) there was a relay going mad under the LHS of the dash as the switch made contact with the metal of the door pillar.
The same didn't happen with the switch in the LHS door pillar.

Does anyone know how the wires from the RHS door switch are routed ? I obviously need to check these.