993tt - Dead Battery
Discussion
Well, after having no problems leaving my car for periods of 3-5 weeks unattended for the last 2 1/2 years, my battery was completely dead after 4 days of inactivity. Last activity was a 5 hour drive, as I said 4 days earlier. Completely dead, nothing.
Battery is a Bosch Silver 74Ah. Taken it out and now recharging using my Optimate. It didn't go into the de-sulphuring cycle, just into the charging cycle so looks like the battery should be ok but not sure yet until I install it back in the car.
Any ideas anyone? Can something just suddenly start to drain the battery out of the blue. It has a PA1000 immobilser/alarm but it's alwasy been there for the last couple of years.
A mechanic in Germany told me that sometimes the clock can cause a current drain situation. Anyone ever heard of that?
Battery is a Bosch Silver 74Ah. Taken it out and now recharging using my Optimate. It didn't go into the de-sulphuring cycle, just into the charging cycle so looks like the battery should be ok but not sure yet until I install it back in the car.
Any ideas anyone? Can something just suddenly start to drain the battery out of the blue. It has a PA1000 immobilser/alarm but it's alwasy been there for the last couple of years.
A mechanic in Germany told me that sometimes the clock can cause a current drain situation. Anyone ever heard of that?
aceparts_com said:
Probably the best thing to do is to connect an ammeter between the earth lead and the battery and monitor it for a while.
I'd expect to see a current drain of less than 1 amp.
I'd expect to see a current drain of less than 1 amp.
Yep, I'll do that once the battery is back in. So that's less than 1 amp with the alarm, clock etc active or is that for the battery before it's reinstalled?
Needs to be quite a bit less than an amp, cos with a fully charged battery at 74Ah you will only get 74 hours before its flat.
Batteries can suddenly decided they are dead, happened to my TT.
For what they cost i replaced it with one from the motor factors.
I would hope your ammeter does not read much above 300mA
Batteries can suddenly decided they are dead, happened to my TT.
For what they cost i replaced it with one from the motor factors.
I would hope your ammeter does not read much above 300mA
Well, my battery has now been on charge for more than 3 days. I'm using an Optimate III charger. It reckons that when the yellow LED is on, it's charging. When the green LED is on it's fully charged. The red LED means it's unrecoverable. So far, only the yellow LED is showing. The spec of the charger says it charges at 1 amp per hour. That means for my 74Ah battery that is 3 days and 2 hours (74 hours).
However, my battery was completey dead before I started charging it - complete blackout. Anyone know how much longer I am likely to wait for full charge?
However, my battery was completey dead before I started charging it - complete blackout. Anyone know how much longer I am likely to wait for full charge?
Its not an exact science when the batteries get old.
The optimate is great ( i use one) but for general charging you would be better with something like a halfords 6AMp charger to get the thing done over night.
Optimate is good for trickle charging a battery to keep it full charged or encouraging a battery to take a charge when its dead and on its back. For the bit in the middle which is when you are shoving a huge amount of charge at it, you need to either drive the car and let the alternator do it or use a bigger proper charger.
Hope this helps
The optimate is great ( i use one) but for general charging you would be better with something like a halfords 6AMp charger to get the thing done over night.
Optimate is good for trickle charging a battery to keep it full charged or encouraging a battery to take a charge when its dead and on its back. For the bit in the middle which is when you are shoving a huge amount of charge at it, you need to either drive the car and let the alternator do it or use a bigger proper charger.
Hope this helps
funny that Silvertt,
my 993 gets the same kind of usage as yours, and yesterday i went to the garage, intent on a long trip and my battery was dead flat too, and i had driven it about 5 days ago. I rummaged around and found an 'old' charger called a 'SuperCharger' by MaxAmp, it say's that it does 4amps. my battery is more or less the same spec as yours, a 'heavy duty' 75 ah. I don't have a manual for the charger, so can any battery boffins give me some idea of when and if, it will fully charge the battery, there are no fancy lights on the charger, just an amp needle, that evey 60 seconds or so, buzzes and then jumps from 0 - to 4 amps, then drops back to 0 again...
my 993 gets the same kind of usage as yours, and yesterday i went to the garage, intent on a long trip and my battery was dead flat too, and i had driven it about 5 days ago. I rummaged around and found an 'old' charger called a 'SuperCharger' by MaxAmp, it say's that it does 4amps. my battery is more or less the same spec as yours, a 'heavy duty' 75 ah. I don't have a manual for the charger, so can any battery boffins give me some idea of when and if, it will fully charge the battery, there are no fancy lights on the charger, just an amp needle, that evey 60 seconds or so, buzzes and then jumps from 0 - to 4 amps, then drops back to 0 again...
Gosh, you guys, do you really want the science ?
Battery chargers designed for lead acid use a constant voltage charger.
As the battery becomes more charged its internal resistance reduces and the amps reduce. Generally when the amps stop reducing you have given it as much as it can take.
As the battery gets older it will still take an amp or two but never reach the lower resistance level and hence be "fully charged"
As batteries get older, their internal resistance increases and their capacity reduces. If you keep charging beyond its need it will overheat and you will loose some of its acid as hydrogen is given off when charging heavily.
Batteries will blow up in your face if you hold a naked flame or spark when you have been charging heavily ( and it will make you deaf for a day or two)
At the first sign of a battery not holding up, i change it especially if its over 5 years old. If you are finding your battery is getting flat it is useful as Aceparts mentioned to check the current drawn when dormant and everything but the alarm and immobiliser is off. If the mA is a few hundred or less its OK but of course will eventually drain any battery, just divide the battery capacity in Amp/h by the current drain in mAmps to determine how long it will go. Remembering you will need about 25% to start the car (depending on temperature) which also drastically affects capacity.
Battery chargers designed for lead acid use a constant voltage charger.
As the battery becomes more charged its internal resistance reduces and the amps reduce. Generally when the amps stop reducing you have given it as much as it can take.
As the battery gets older it will still take an amp or two but never reach the lower resistance level and hence be "fully charged"
As batteries get older, their internal resistance increases and their capacity reduces. If you keep charging beyond its need it will overheat and you will loose some of its acid as hydrogen is given off when charging heavily.
Batteries will blow up in your face if you hold a naked flame or spark when you have been charging heavily ( and it will make you deaf for a day or two)
At the first sign of a battery not holding up, i change it especially if its over 5 years old. If you are finding your battery is getting flat it is useful as Aceparts mentioned to check the current drawn when dormant and everything but the alarm and immobiliser is off. If the mA is a few hundred or less its OK but of course will eventually drain any battery, just divide the battery capacity in Amp/h by the current drain in mAmps to determine how long it will go. Remembering you will need about 25% to start the car (depending on temperature) which also drastically affects capacity.
porsche4life said:
Gosh, you guys, do you really want the science ?
As the battery becomes more charged its internal resistance reduces and the amps reduce. Generally when the amps stop reducing you have given it as much as it can take.
As the battery becomes more charged its internal resistance reduces and the amps reduce. Generally when the amps stop reducing you have given it as much as it can take.
Sorry '4life,
I'm still none the wiser...
every 60 secs or so, my needle jumps from 0 - to 4 amps, then drops back to 0 again...
Do you think this means the battery has had it, or is my battery charger juct buidling up some energy and then zapping it with some juice? It is one of those batteries with screw caps in the top, do you think I should put some distilled water in it?
I don't know why, but I have a feeling this battery is not comepletly kaput. I have a feeling i left the side lights on the car, but didn't notice them in a large well lit garage.
My battery is 2 1/2 years old and have had zero problems with it until last week. It's a Bosch Silverline sealed battery. It drained completely after 5 days and it's the first time it's done that. During the winter, it's always connected to an Optimate when not in use. During the summer, it gets more use but there are some periods where it won't get used for between 1-3 weeks. This has never been a problem before so after 2 1/2 years of problem free starting:
1) Is it possible for the battery to suddenly completely drain after 5 days inactivity (without other electical issues)?
2) Would running the car in some of the hot temperatures recently, damage the battery?
3) Why a charger that supposed to charge at 1 amp per hour hasn't full charged my 74Ah battery after 90 hours charging?
1) Is it possible for the battery to suddenly completely drain after 5 days inactivity (without other electical issues)?
2) Would running the car in some of the hot temperatures recently, damage the battery?
3) Why a charger that supposed to charge at 1 amp per hour hasn't full charged my 74Ah battery after 90 hours charging?
1) Yes, they have finite lives and don't always degrade slowly. If a cell shorts out (due to a broken plate) then the battery's history. If it can be done it's worth checking the fluid level and it's always worth checking to see what the alternator's output voltage is. Anything more than 13.5-14 volts and it'll cook your battery and possibly some electronics as well. You alternator could have also have started to go meaning your battery wasn't being charged for part of your journey.
2) No, the weather shouldn't be an issue per se. But almost as many batteries die in the summer as in the winter. Heat and higher electrical loads do take their toll over time.
3) If there's a shorted plate or lack of electrolyte no charger will ever be able to recharge the battery. And I'm not sure that trickle chargers can effectively charge a deeply discharged battery.
Worth checking:
battery fluid level if poss
current draw with everything off
voltage level with engine running
tightness of battery cables
state of alternator belt
2) No, the weather shouldn't be an issue per se. But almost as many batteries die in the summer as in the winter. Heat and higher electrical loads do take their toll over time.
3) If there's a shorted plate or lack of electrolyte no charger will ever be able to recharge the battery. And I'm not sure that trickle chargers can effectively charge a deeply discharged battery.
Worth checking:
battery fluid level if poss
current draw with everything off
voltage level with engine running
tightness of battery cables
state of alternator belt
police state said:
every 60 secs or so, my needle jumps from 0 - to 4 amps, then drops back to 0 again...
Do you think this means the battery has had it, or is my battery charger juct buidling up some energy and then zapping it with some juice? It is one of those batteries with screw caps in the top, do you think I should put some distilled water in it?
I don't know why, but I have a feeling this battery is not comepletly kaput. I have a feeling i left the side lights on the car, but didn't notice them in a large well lit garage.
That charger sounds suspect. Either try it on a known working battery and see how it behaves or try a different charger.
Edited by phelix on Tuesday 25th July 13:33
SilverTT.
Its possible but 2.5 yrs is not much is it.
I would not take it your optimate is gving out 1 Amp unless you measure it with an ammeter.
Suggest go get the halfords charger.
Connect it and make sure the amps have come down to less than 1 amp, should be close to fully charged.
Then switch on headlights and see how long before it discharges the battery.
Then do the maths. If you get more than 6 hours its as good as new.
cheers
Its possible but 2.5 yrs is not much is it.
I would not take it your optimate is gving out 1 Amp unless you measure it with an ammeter.
Suggest go get the halfords charger.
Connect it and make sure the amps have come down to less than 1 amp, should be close to fully charged.
Then switch on headlights and see how long before it discharges the battery.
Then do the maths. If you get more than 6 hours its as good as new.
cheers
Gassing Station | Porsche General | Top of Page | What's New | My Stuff