BILL BAUER wrote in a message to Mike Nash:
 BB> I still definitely need much better testing methodologies and 
 BB> of course much better salvaging techniques. I am currently 
 BB> using the little Snapon (TM Snapon tool Co.) battery testers. I 
 BB> have two of them and although they work well and are pretty 
 BB> accurate, they aren't totally reliable as far as telling the 
 BB> actual condition of the battery. 
Do you know offhand how much of a load these put on a battery?
 BB> I am thinking that maybe I need to use a digital voltmeter to 
 BB> check the amount of voltage drop during a given period of time 
 BB> with the load switch depressed on the meter. I don't know what 
 BB> would be the lower limit the voltage ought to not drop below 
 BB> under load to be sure that the battery won't fail in service 
 BB> for a quite a while. 
It's dependent on temperature,  but the testers I used to use were marked 
with colored scales and went,  typically,  to 9.6V (for a 12V battery) as 
being "the bottom of the green".  The scales were also marked for 6V 
batteries as well.
That particular unit had two meters in it,  one to show you the voltage and 
the other to show you current being supplied to the load.  The load itself 
was a big knob that cranked down the pressure on a carbon pile,  a good bit 
different from the other testers I've see.  The one I occasionally use at the 
place I'm working now looks like the insides of a toaster when you hold that 
switch for more than a couple of seconds,  and gets quite warm.
The nice thing about that other tester was you could either pull it down to 
the bottom of the green and read the cranking amps the battery was putting 
out,  or try for the rated cranking amps and see where the voltmeter ended 
up, still in the green or otherwise.
 BB> I tend to think that if a battery dropped below say 10 or 11 
 BB> volts while being load tested that it would be an unacceptable 
 BB> amount and the battery needs to go to the junk rather than to a 
 BB> customer, but I don't want to set the lower limit too high 
 BB> because I would end up junking a lot more batteries than now. A 
 BB> difference of maybe even a 1/2 a volt here could be the crucial 
 BB> factor between chunking a good battery when it might have given 
 BB> excellent service.
Yep.  See above for my figures.  Again,  it depends on the load and on what 
the battery is rated at too.  This doesn't seem to be taken into account with 
those small load testers,  somehow.
Rather than an absolute value (will it crank?),  I tended a lot to look at 
the behavior of the battery.  Pull the voltage down to a particular place 
while you're yanking a bunch of power out of the battery under test,  and 
both of the meters oughta hold pretty steady until you back that load off.  
Load one and watch the meters take a nose dive,  and you've got a bad 
connection inside the battery that's heating up,  which will often show up as 
one cell (or two adjacent cells) boiling.  Lots of corrosion in a car is 
often a sign of this, if the battery hasn't been over-filled.
I remember one that came in which, without even being loaded,  was blowing 
boiling sulfuric out the vent at the end of the case (a Delco,  no caps).  I 
let that puppy sit ouside and cool off for a good bit before I put it in the 
scrap pile...   
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