21 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHDid battery tender kill my alternator / cause electrical fault?
Reported or suspected cause
present
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause · Original poster
Oddly, the car sounds like a rattlesnake is living in it while the issue is present.
Did battery tender kill my alternator / cause electrical fault?
Read full discussion summary
Leading evidence: 'present' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'present' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check than taking it straight' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
I use a charger/auto maintainer specifically made for AGM batteries.
Did battery tender kill my alternator / cause electrical fault?
related
Suggestion or failed attempt
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Did battery tender kill my alternator / cause electrical fault?
Check than taking it straight
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
I bet that's a cheaper first check than taking it straight to a shop.
Did battery tender kill my alternator / cause electrical fault?
Run agm or a lithium battery
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
If you want to run a AGM or a lithium battery on a Porsche to make it work correctly you likely need to re calibrate how the charging system works, AGM needs about 1 volt more than liquid lead acid to really get a full charge, some cars you can add a diode to fool the system in to charging a bit higher,, some (cough cough german) cars the ECU is just too entangled in the process to really work at 100%.
Did battery tender kill my alternator / cause electrical fault?
Run agm or a lithium battery
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
If you want to run a AGM or a lithium battery on a Porsche to make it work correctly you likely need to re calibrate how the charging system works, AGM needs about 1 volt more than liquid lead acid to really get a full charge, some cars you can add a diode to fool the system in to charging a bit higher,, some (cough cough german) cars the ECU is just too entangled in the process to really work at 100%.
Did battery tender kill my alternator / cause electrical fault?
Use charger/maintainer, in fact, the real problems start
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
100's of people put their Porsche's in winter storage and I have never heard of a problem from using a charger/maintainer, in fact, the real problems start because they don't do it (i.e.
Did battery tender kill my alternator / cause electrical fault?
Coverage and how to read this overview
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
21 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
Took the car out for a short drive, nothing for first 3 mins, then dash lights back on (see video) then 3 mins later all back to normal again.
Hi fellow PCar fans,
I was away for the past 6 weeks and connected a new Battery Tender Junior (12v, 750mA) to my �01 996 C2 (with only 31k miles).
Upon return, eager to enjoy the car, on my 2nd drive of the day, the battery warning light, along with ABS, brake fluid and other lights started flashing and voltage dropped to around 12-ish, seemed like the car was no longer charging. 5 minutes later, it felt like the alternator kicked in again, voltage back nearer 14, warning lights went out and Kermit was himself again.
Next day, 2 mins into my drive, the Christmas tree dashboard returned, same symptoms. Oddly, the car sounds like a rattlesnake is living in it while the issue is present.
Any chance the battery tender messed up the electricals? Seems VERY strange�
Anyone experience anything similar before? Ideas on where to troubleshoot first?
Thanks!!!
Rick
I'm a new 996 owner and I asked my Indy about using a tender. His response was that he was opposed to hooking up the car to anything electrical. Who am I to argue?
No reason to not use a tender but to be safe, and because it is simple, i just take the cables off the battery when i use it.
No idea if your issue is related.
I use a charger/auto maintainer specifically made for AGM batteries. I use it all the time with no problems. First place to check is your battery. How old is it? What type is it? Most auto parts stores will load test the battery for you. You might have a broken cell in your battery. Check to make sure the battery connections are clean and tight.
Is this like a 996 or Porsche issue? I don't understand. 100's of people put their Porsche's in winter storage and I have never heard of a problem from using a charger/maintainer, in fact, the real problems start because they don't do it (i.e. my battery is dead and I can't get in the car!). Let's start with an automotive museum. They don't drive those cars around and most if not all are on a charger/maintainer.
The battery maintainer is NOT the cause of the issue. People have been using them on these cars for literally 20 years with no issues. Plus I have confidence in my electrical engineering degree to confirm it unless you have a faulty maintainer pumping in some weird current, and even then it would be a stretch since the battery acts as a load shunt in this case.
The Battery Tender, nor any other 12v Charger designed for your Car Battery will harm you alternator at all... reason is that they put out about 14.xx Volts Max. and a Cars System is designed to handle more volts...up to 16.5v (generally speaking on most electrical parts. and occasional spikes from the Alternator itself, and the charge from a Battery Tender Jr. is very mild meaning low Current not to high voltage.
With that being said a Battery Tender Jr. is a very low-end charger with a not very sophisticated charging profile or functions, and they really can "cycle" a battery more than needed. . Might want to get something a bit more modern and with charging profiles and maintenance that isn't quite so basic if you get a newer battery. CTEK and Optimate are good brands.
The alternator on mine died 20 minutes off the used car lot. The assumption is that it was original and probably on the list of those "things" that likely should be done in the interest of reliability due to age.
Thanks all for your comments / advice. Took the car out for a short drive, nothing for first 3 mins, then dash lights back on (see video) then 3 mins later all back to normal again. No loose wiring, battery looks good and only 2 years old. Ignition switch feels totally normal. Car has 31k mi only.
Weird to have this issue right after having had it connected to the tender.
Will need to take it into the shop but concerned this could turn into an expensive wild goose chase!
Thanks again,
Rick
Did you follow the advice to have your battery tested? Most autoparts stores will do it for free.
It doesn't even have to be in the car.
I bet that's a cheaper first check than taking it straight to a shop.
Given the sounds you hear, it definitely sounds like an alternator issue though.
Or, how does your car start when already hot? The alternator feeds power back through the pole on the starter motor to the battery/main bus. The 12v wire at the Starter is known to corrode badly. It usually shows up as hard starting when hot. But I wonder if it couldn't cause an intermittent or weak alternator connection? Wouldn't cause rattling noises though.
Put in a new battery yesterday ($300!!! Yikes). Solved the dashboard lighting up like Christmas, car is able to drive a charge now. Haven�t noticed any weird noises either, though really not sure why a failing battery would have been responsible for the noises I did experience.
Anyhow, thank you all for your advice and insights!
FWIW,, the symptoms are classic of EFI Porsche BMW and Audi when the battery gets a bad cell.
If you want to run a AGM or a lithium battery on a Porsche to make it work correctly you likely need to re calibrate how the charging system works, AGM needs about 1 volt more than liquid lead acid to really get a full charge, some cars you can add a diode to fool the system in to charging a bit higher,, some (cough cough german) cars the ECU is just too entangled in the process to really work at 100%. I would run a standard high end sealed battery unless you do some pretty deep homework.
This is a source reference. Confirm exact model applicability in the original material.
