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Everyone's normal is different Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 14 Feb 2002 10:53:26
In Reply to: Voltage, Ed, Wed, 13 Feb 2002 22:07:59 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There are A LOT of variables that affect the EDU voltage reading, and even more for the measurement of startup voltage. Having owned a few 9000's both turbo and normally aspirated, I can say with authority that each one is different.
My '92 NA shows low 9 volts STARTING with a brand new, well-charged battery, dropping into the high 8 volt range as the battery ages. With this particular car, I know mid 8 volt range is fine. When the voltage starts dropping below about 8.5, I know the battery is on the way out.
Two other 9000's (both '88 9000T) had higher Starting voltages. One showed 11 volts, and once it showed 10.0, I knew it was time to replace the battery or risk being stranded on the spot. The other would startup at 10.0 with a new battery, and anything below 9.0 was trouble.
So what does this mean? It means that no matter what absolute number people tell you 10.0, 9.5, 3.14159..., even what it says in the manual, is very nice, but may or may not apply to your car. The EDU voltage is NOT an accurate voltmeter. What you need to learn is what is normal for Your car, so when you see something else, it's time to take action.
It's normal to see a lower starting voltage on a cold day, because the battery has less capacity and the engine is harder to turn (thicker oil). Get to know what's a typical starting voltage for your car. Give it benefit of the doubt on a really cold day. Listen to how fast the engine is turning - if it's barely turning over, you don't need a voltmeter to tell you the battery is tired. In general, you'll see a relatively constant starting voltage through the life of the battery, and near the end of the battery's life, you'll see the voltage tumble. So you're not looking for some absolute voltage, but for a trend - it'll drop slowly over the life of the battery, and when it suddenly is a lot lower, and it's cranking slower, it's time for a new battery.
The same is true for the running voltage. When cruising along at speed, voltages below around 13.0 or above 14.7 aren't good. But after a while you'll get to know your car, and when you see a TREND change, then start to look at why.
I hope this helps
posted by 140.157....
, Thu, 14 Feb 2002 10:53:26 <-- Viewing This Message
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