Battery holder drop voltages?

Recently my wireless mouse stop working, so I open it to inspect around, and I found out that at the connecting terminal between the battery holder and the mouse PCB, the voltage is only 1V (unplugged from the mouse itself) , but when I take the battery out to measure, each of the battery got 1.5V. And when I measure on the 2 metal ends (of the holder), my multimeter read 1.7V. So, what's wrong with it? Can anyone help me with this? It's really the first time I have a situation like this

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verence2 years ago

When you take the battery out, there is no load anymore on the battery and you measure a higher voltage. When the battery is inside the device it's normal to measure a lower voltage due to the internal resistance of the battery. A good (if a bit lengthy) description is here. TL,DR: Measuring batteries without load is useless.

Your battery is dead. (Or there is a short circuit inside your mouse so that the load is too high). Try new batteries.

Mad Fox (author)  verence2 years ago

actually I take it out and measure the battery when it's in the holder. And the holder has been disconnected from the mouse itself

verence Mad Fox2 years ago
So wait, I'm confused.

You take the battery holder out of the mouse, so that it is not any more connected with the mouse's PCB? And just by inserting the battery into this holder the voltage drops? Strange. Even a high resistance due to corrosion should not produce a significant voltage drop as no current is flowing (as you are using a modern DMM, I hope)

Sounds like there is any kind of short circuit inside the holder.
Mad Fox (author)  verence2 years ago

yeah, that's what make me confused. It is not connected to the PCB anymore but the voltage drop significantly. I tried to scrap off the corrosion using some sanding paper, and when I reconnected the battery, the voltages was 2.7V..... strange..... but it is still not enough to power the mouse anyway....

What verence is trying to explain is:

You cannot measure batteries while not connected. It doesn't matter if they are in a battery holder or whatever. They can only be measured while powering some kind of device.

To measure a battery (1.5V), use your voltmeter and connect the leads with a resistor. The value of the resistor should be around 100 ohms. For 4.5V (3 batteries) use resistor around 300 (3x100) ohms.

With the connected leads of the multimeter, now measure the voltage of the battery. The resistor will simulate a circuit. It's just an estimate, different circuits will draw different amounts of power, but you'll get a usable estimate of the voltage inside your device.

Under 1.0V the battery is dead. If the device's manual tells you you shouldn't use rechargable batteries, the battery is dead under 1.2V, but can still be used for other low power devices, such as leds, calculators and analog wall clocks.

If the device holds more than 1 battery, switch all batteries at the same time. Don't use old and new batteries together.

Forgot to add: You can get strange readings when measuring a not connected battery. You can measure the battery in the holder the same way I described above.

To test the battery holder in an easy way:

Take the battery out of the battery holder. Connect the inside of the battery holder with a wire. (In other words: replace the battery with a wire.)

Next, measure the resistance of the holder (without the resistor connected leads!). A resistance in tens of milliohms is acceptable.

If the resistance is too high, check the connections of the battery holder. Clean them with aceton or alcohol, or, if corroded, use a small amout of flux, and let it rest for some time. Then clean it with aceton or alcohol. Or just buy a new battery holder.

Contact problems...

Mad Fox (author)  Downunder35m2 years ago

Yeah, it's a bit rusty so I scrap it off using some sanding paper but the problem remain. I'll try to get the rest of the rust off. Any other suggestion?

Replace the wires from the pads to the circuit board.
If there is a lot of corrosion these wires be faulty as well.

iceng2 years ago

AA Batteries with no load (except meter) will almost always show full voltage.

That is why some brands had a TEST Feature that let you press two points and it l loads a shaped resistive strip under a liquid crystal to show the battery charge level

AA1.JPG

Bad batteries.

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