Re: Lead acid battery tester

Carlos E.R. <robin_listas@es.invalid> wrote:

Hi,
 
I bought yesterday a battery for my UPS at a shop that specializes in
batteries. I had my old battery there, so to get the same type, and I
asked the chap if he had a voltage meter. Something like that, he said.
He brought out a special meter with huge clamps, attached it, and said
the batter had 13.6 volts. Then he tested "load" and said said the
battery gave out only 20 out of 100. I don't know what he was actually
measuring, some time of current over a resistor measurement, I suppose.
It is adjusted for the size of battery.
 
Do you know what meter could be that thing?

There are car battery testers that almost short-circuit the battery
through a convoluted strip of metal which acts as a load resistor to
simulate the current drawn by a starter motor.  They incorporate a
voltmeter so you can watch the terminal voltage fall on load.

It sounds as though the voltmeter in your case was calibrated with some
arbitrary scale of 'goodness', based on 100% for a battery in perfect
condition.  The actual voltage drop will depend on many things, such as
the battery capacity (which yours was compensated for) and the ambient
temperature, so interpreting the readings calls for a degree of
awareness and skill that most mechanics don't have. 

However, it is usually  a good enough indicator for obvious cases of
dying batteries that collapse after a few tens of seconds or boil-up
under heavy load.


--
~ Liz Tuddenham ~
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www.poppyrecords.co.uk