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Thread: battery voltage required for starting Reply to Thread
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Topic Review (Newest First)
10-16-2012 04:00 PM
BrApple
Quote:
Originally Posted by TboneZX3 View Post
If you're only dropping to 10 while cranking, I would suspect something other than the battery. 10 volts is good voltage for a cranking load.
This was after charging the battery and driving to and from work yesterday and around on Sunday. The starting voltage I noted saturday was lower on the battery. But I agree, the battery seemed fine when I tested it yesterday.
10-16-2012 03:22 PM
TboneZX3
Quote:
Originally Posted by BrApple View Post
Anyway the test mode was very useful. I used it to check the voltage while starting and it got into the mid 10s for a moment when cranking.
If you're only dropping to 10 while cranking, I would suspect something other than the battery. 10 volts is good voltage for a cranking load.
10-16-2012 07:35 AM
BrApple
Quote:
Originally Posted by Daytona Coupe View Post
Voltage would probably have to drop below 10 to prevent the ignition from working properly and if that was happening it would crank much slower - not just a little slower.
compareed to normaly it was pretty slow. I'll have to try to get it on video next time it happens if it does. Best I can discribe the difference is a normal start is sounds like it turns over 4 or 5 time in about 5 seconds. When it didn't want to start it sounded like it was turning over once maybe every 5 or 10 seconds. Times are not exact, but hopefully help explain the difference between how the car normally cranks over and what it was doing.

Anyway the test mode was very useful. I used it to check the voltage while starting and it got into the mid 10s for a moment when cranking. I also loaded up the car as much as possible, defroster, headlights and high beams, fan on high and at idle and ~2 krpm the voltage was solid at 14 volts. Checking at the battery yeilded similar results for for starting and when I checked the voltage when loaded.
10-15-2012 11:07 PM
Daytona Coupe Voltage would probably have to drop below 10 to prevent the ignition from working properly and if that was happening it would crank much slower - not just a little slower.
10-15-2012 04:22 PM
BrApple
Quote:
Originally Posted by Daytona Coupe View Post
If you have enough power to crank the engine at a reasonable speed (sounds like you do) - then you have enough voltage for the ignition & computer to work. Voltage is not your problem.
That is the thing, when it didn't start it didn't crank as fast as it normally does. However everything electronic worked.

I do feel there maybe something else going on here, I'm going to do some testing of my own on the battery and then take it to the dealer.
10-15-2012 01:31 PM
Daytona Coupe If you have enough power to crank the engine at a reasonable speed (sounds like you do) - then you have enough voltage for the ignition & computer to work. Voltage is not your problem.
10-15-2012 09:34 AM
TboneZX3
Quote:
Originally Posted by BrApple View Post
Would a voltage lower then 12.5~12.6, which is normal for a good 12 volt battery effect the ability of the car to start.
Not necessarily, no. As already stated, open-circuit (unloaded) voltage alone is not a good indicator of the battery's charge status.


Quote:
Originally Posted by BrApple View Post
That is why I am wondering if starting it twice and only letting it run for maybe 5 minutes total would ahve caused a lower then normal charge on the battery and therefore a starting problem.
"Lower than normal"? Yes, probably, but if the battery is good, that type of use wouldn't reduce the charge enough to cause a no-start condition. I could do that 5 times in a row with a good battery and it would still start.
10-15-2012 07:53 AM
BrApple my observation from this morning is that when I tried to start the car yesterday the engine did not turn over as fast as it normally does. It turned over much quicker this morning.

So to me it seems like the voltage as just alittle low to start the car, but was more then enough to crank the engine and run all of the electronics.
10-14-2012 09:09 PM
BrApple Yes a load test is a good idea.

However, you are partly saying what I was getting at. Would a voltage lower then 12.5~12.6, which is normal for a good 12 volt battery effect the ability of the car to start. Again everything else worked correctly. The engine did crank over, it just didn't start. That is why I am wondering if starting it twice and only letting it run for maybe 5 minutes total would ahve caused a lower then normal charge on the battery and therefore a starting problem.

I checked the voltage across the battery while running and it was 15 volts. So the alternator is charging correctly. Also it hasn't had an issue starting at all for the rest of today.
10-14-2012 12:30 PM
Daytona Coupe Voltage at rest won't tell you much about the battery's state of charge, it needs to be checked under load. Have someone measure voltage at the battery while you are cranking it - it should stay above 11v while cranking. Even over 10 will probably still allow it to start. If voltage stays high while cranking, your problem is likely somewhere else.

Get the battery fully charged and the have it load tested - this will tell you if the battery is bad or not. If the battery tests ok, then load test the alternator. If both check ok, you may have some other electronic issue that will probably require a trip to the dealer
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