Re: [DML] Re: Bad Battery / Good Alternator

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

Quoting Elvis <elvisnocita@xxxxxx>:

>
>> Regarding good alternators on bad batteries: If the plates inside a
>> battery are dead, but the alternator itself is good, it is not going
>> to produce 13.5 volts (typical charging nomenclature). I defy you to
>> produce charging voltage on a dead battery (not a battery that
> simply
>> needs specific gravity, but one that has bad plates).
>
> Is there any real explanation for that ????
> What do you mean with dead plates ? I had dead batteries in my car
> before and I am still alive - and my voltage gauge still showed
> 13.8V when the engine was running at a bit higher speeds than idle !
> (of course NOT with all the loads on that I could find !)
> What are we discussing here ? Do we need to discuss basic high school
> electricity laws ? Starting at Ohm's law ?

I don't think Bill would know what you meant if you started referring  
to current by the letter "I" :-)

Bill, a dead battery (as opposed to a flat battery) is almost always  
an open circuit, not a dead short. The alternator relies heavily on a  
battery's capacitance to regulate correctly, and in this respect, even  
a dead battery is often still good. Generating a potential (measured  
in Volts) does not require a load or current flow. However for an  
alternator to provide a stable potential, it does need a load. So if  
your battery's dead, turn the lights on... there's a nice resistive  
load in the order of a couple of ohms.

Martin






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