Can a battery that is completely shot still have a full voltage?

[rboggs10]

This is sort of an engineering question and sort of not but it involves me possible replacing the lithium-ion battery in my iPod Touch. My iPod will not turn on no matter what I do. My iPod says that there is no battery life left in the battery, yet when I took it apart and removed the battery, my volt-meter shows that the battery has a voltage of exactly 3.7 volts which is the battery's factory voltage. To me it seems that it could be a shot battery but the fact that the battery has 3.7 volts says otherwise. I want to know if it is my battery that is the problem before I pay to order a replacement.

 

[phinds]

A battery with zero load (and a multi-meter is very close to zero load) can show full charge but as soon as you add a load, the voltage can drop precipitously if the battery is basically depleted.

You need to get a resistor that simulates roughly the load of the ipod and put it across the batter and THEN see what the voltage reading is.

 

[Integral]

A battery with zero load (and a multi-meter is very close to zero load) can show full charge but as soon as you add a load, the voltage can drop precipitously if the battery is basically depleted.

You need to get a resistor that simulates roughly the load of the ipod and put it across the batter and THEN see what the voltage reading is.

I will quibble with the use of charge here. A voltmeter can never tell you about the charge, it only shows potential. So a dead battery when using a "good" voltmeter will show full potential. As soon as you attempt to draw current (charge) from the battery the terminal voltage will drop.

A "good" voltmeter, that is one with a very high input impedance is NOT a "good" meter to check batteries with. Better off with a old analog meter that draws a measurable current for checking batteries.

 

[rboggs10]

Thanks for the responses, that makes sense how the volt-meter won't really show whether or not it is a good battery. How about I try removing the battery again and try using to power a simple LED driver? Would seeing if the LED lights up significantly be a fairly good determination of whether or on the battery is completely shot?

 

[phinds]

I will quibble with the use of charge here. A voltmeter can never tell you about the charge, it only shows potential.

I absolutely agree. I mis-spoke. Meant to say voltage, not charge. My dyslexia kicking in once again.

 

[phinds]

Thanks for the responses, that makes sense how the volt-meter won't really show whether or not it is a good battery. How about I try removing the battery again and try using to power a simple LED driver? Would seeing if the LED lights up significantly be a fairly good determination of whether or on the battery is completely shot?

Yeah, sounds good to me.

 

[Integral]

Check terminal voltage while it is drawing current.

The best route is just to replace the battery, rather then spending a lot of time on something that is obviously bad.

 

[dlgoff]

Here's a good battery resource. They're not trivial.

http://batteryuniversity.com/learn/

 

[rboggs10]

Check terminal voltage while it is drawing current.

The best route is just to replace the battery, rather then spending a lot of time on something that is obviously bad.

It is just that I want to make absolutely sure that the battery is the problem before ordering one. I know that they aren't too expensive, I just don't have a large budget. I will test the battery as you have suggested tomorrow.

 

[rboggs10]

Here's a good battery resource. They're not trivial.

http://batteryuniversity.com/learn/

Thanks for that post. That looks like a site that will be a good reference for me.