Actually Dave Not So :)
12 V lead acid at REST
12.6 100%
12.3 50%
11.7 10%
Even though you are correct that you can see as much as 15 volts under
charge and 13.5 with surface charge it is little indication of the batteries
state. Give it a day to calm down and you will see the above numbers.
Following a full charge you might see the following:
13.5 100%
12.8 50%
11.8 10%
So, if you see 13.5 to 15 volts under charge and 12.6 to 13.5 with the
engine off then you are good to go.
You are looking at the range of 15 to 12.6 or about 2.4 volts difference,
still hard to see on a +/- 8 to 16 volt meter probably made in China and is
+/- 20% anyway.
An amp meter will show the net amount of charge minus drain, as long as you
have a good battery and no dead cells and the amp meter stays on the + side
of 0 you are generally good to go. But it might also be over charging a
defective battery which will boil it dry and leave you stranded with
nothing. Buy a new lead acid battery every two or three years or get a gel
cell battery that might last you 10 if you are kind to it.
Here is a good link to the facts about lead acid batteries.
http://www.wind-sun.com/PDF_Files/battvoltandsoc.pdf
Mark
Nashville
http://www.arrestmered.com
----- Original Message -----
From: "Dave G." <dmg@bossig.com>
To: "Mark" <mark@nashvilletn.org>; <spridgets@autox.team.net>
Sent: Monday, May 07, 2007 6:47 PM
Subject: Re: Ammeter or voltmeter?
Mark,
Not so...
A fully charged Lead-Acid battery will show 13.8V at no load.
Under charge it can go up to 15V.
A fully discharged battery could show anything between 11V to 6V and
even lower depending on the condition of the battery..
A voltmeter can indicate when you have a dead or shorted cell.
It can also be an indicator of the condition of your system when it
momentarily drops from 12V to around 6V on cranking the starter...
There are a few other things I could think of... but that's enough to
start with.. :-))
Dave G.
> the voltage difference between a
> charged battery and a discharged battery is only about 2 volts which
> is hard to see on a analog car voltmeter anyway.
|