--- Jeff Walther <[EMAIL PROTECTED]> wrote:
You need to check the battery voltage with the battery installed in the machine and the machine unplugged or the outlet (power strip) turned off. An unloaded voltage reading isn't very useful.
Hi Jeff- good to hear from you. I put the battery in place, machine unplugged. Using a digital autorange multimeter, I keep getting a reading of 1.356. The set up was the same as when I tested the battery under no load conditions where I got the 3.2 reading. Not being an "electrically literate" person, I don't understand this. Do I assume that the range of the results are to be interpreted by moving the decimal and reading this as 3.56?
No, it means that your battery is flat.
I'm not quite sure how to explain the physics of it but the empirical model is that voltage sources are lower when in use than they are when not in use because they are not perfect.
A perfect voltage source would be 3.2V (or 3.6V) whether it was connected or not.
Hmmmm. Let's see. Let's try a water pump analogy. Or similarly, the water mains. Yes, let's use the water mains. So you have water supplied to your house at a certain pressure depending on where you live and how tall the water tower is, etc. Most of the time the water pressure at your house is pretty much the same. But if there were a fire down the street and three fire trucks were hooked up and all your neighbors were watering their lawns, you'd expect to pretty much have no water pressure at your house, right?
Now imagine if the main pipe coming from the water tower was reduced to garden hose size. Then one neighbor watering his lawn is pretty much all it would take to reduce your water pressure.
A flat battery is a lot like a water tower with a pipe the size of a garden hose. The pressure is fine until anyone tries to use any of the water.
Similarly, with a flat battery the voltage looks fine until there is a load draining off any of the potential as current). Some batteries are so flat that they read low even when unloaded, but not all flat batteries are that flat.
This is why one must test a battery under load if one is testing it with a voltmeter. The voltmeter does not provide any load itself. Voltmeters are intentionally designed to put no (well, very very little) load on the thing that they are testing so that they do not affect the results.
I hope that helps.
Jeff Walther
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