Re: battery - alternator charging questions

Your Davis car chip is reading the voltage from the computer which has shown
low on all testers I have tried. Use a good digital voltmeter to test the
voltage at the battery. You should get around 14.5 volts with the headlights
on and running about 2000 rpm...


"Lawrence Glickman" <Lawrence_Glickman@xxxxxxxxxxx> wrote in message
news:nqdgj19cc7m0akfdv65174pac6fcome3sa@xxxxxxxxxx
> On Mon, 26 Sep 2005 16:49:08 GMT, "Bill" <cantstand@xxxxxxxx> wrote:
>
>>Hello. I suspect my alternator is not charging my battery. I haven't
>>used
>>this car since April of this year so the battery had run down to 2 V (I
>>measured it with a volt meter). The battery had been connected to the
>>car.
>>
>>I got it charged about a week ago at a car repair place. When I got it
>>back, I measured the battery voltage with my voltmeter to be 12.75 V (with
>>the engine not running).
>>
>>I haven't used it all that much since then (few trips around town) but now
>>the battery voltage is about 12.25 V (with the car not running). When I
>>test the voltage with the engine running, it's slightly less than when
>>it's
>>not running. Shouldn't it be more since the alternator is sending it
>>current?
>>
>>What I want to do is get an ammeter and hook up the ammeter between the
>>cable from the alternator to the positive post on the battery. Then get
>>the
>>car running and see if any current is flowing from the alternator to the
>>battery. The question I have is what should be the current (roughly
>>speaking) flowing from the alternator to the battery?
>>
>>Are there any easy tests that will tell me if the alternator rather than
>>the
>>battery is faulty (or vice-versa) such as turning on the lights when the
>>engine is running? If the lights dim when the engine is running, does
>>that
>>automatically mean the alternator is not charging? Could the problem be
>>the
>>battery's not holding the charge that the alternator is sending it?
>>
>>Thank you for any help in answering any of the questions I posed! Take
>>care,
>>
>>Bill
>>
>
> Just use a voltmeter. With the engine off, you should see about 12.5
> volts, which is considered *normal*. 12.0 volts means the battery is
> Low and needs to be charged.
>
> With the engine running, my alternator delivers 13.8 volts, so that is
> what I read at the battery terminals. 14.0 is *normal*, 13.5 volts
> measured at the battery terminals with the engine running is
> considered *low* alternator output.
>
> So in my situation, I have 13.8 volts ( according to my Davis Car Chip
> ) showing up at the battery from the alternator, I am just within a
> whisker of not having enough voltage delivered. I consider what I'm
> getting to be just right. I'm 2/10ths of a volt short of *normal*
> which is good enough for me.
>
> Do these very very little voltage values matter? YES !!!
>
> If your engine idle is very very low, I can see a problem with a
> *good* alternator not putting out the proper voltage.
>
> Lg
>


.

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