Battery Voltage Drop Off

Hi,

I heard that the voltage drop-off point is when the battery stops suppliying battery. But when I did my experiment (9V battery connected to a resistor) and got under 4V what is the drop-off for enengizer the LED still lit. I also tried it when I was at around 1V.

One more question. When I disconnected the battery overnight, I found that the voltage increased. Can you point me please to a site that explains why this happens?

Cheers,
Karol Krizka

roadkillbunny said:

Hi,

I heard that the voltage drop-off point is when the battery stops suppliying battery. But when I did my experiment (9V battery connected to a resistor) and got under 4V what is the drop-off for enengizer the LED still lit. I also tried it when I was at around 1V.

Click to expand...

The point where you decide the battery is flat varies on your application, alkaline and NICAD's drop off very suddenly at the end of their life.

I would probably consider a 9V battery flat at 7-8V, if it's feeding a 7805 regulator, 8V is probably where the 5V rail will start to drop.

You can view some discharge tests I did years ago at .

One more question. When I disconnected the battery overnight, I found that the voltage increased. Can you point me please to a site that explains why this happens?

Click to expand...

I couldn't tell you the chemical reason why it happens, but if you leave a battery it will recover very slighty - for a remote control it may allow you to get one extra button press. But it is more a question of it's voltage recovering, rather than it's current providing capacity.[/url]