I placed a lithium ion battery in a battery recharger. I let it recharge for a little bit. Then the light turned from red to green. I measured the battery voltage, it was 3.98 volts. That means it's fully charged?

 

I placed a lithium ion battery in a battery recharger. I let it recharge for a little bit. Then the light turned from red to green. I measured the battery voltage, it was 3.98 volts. That means it's fully charged?

Hi M,
Depending on which charger you have, some let you know how many watt/hrs are in the cells.
A good Lithium cell should charge to approx 4.2Vmax.
C.

 

Hi M,
Depending on which charger you have, some let you know how many watt/hrs are in the cells.
A good Lithium cell should charge to approx 4.2Vmax.
C.

So if it does not charge to 4.2 volts, that indicates it's faulty?

 

So if it does not charge to 4.2 volts, that indicates it's faulty?

Hi M,
Either the battery or charger is faulty, or worn out.
Charging Lithium must be done properly for safety. A good charger will charge up to 4.2V and cut off, also if the cell gets hot it does the same.
They can catch fire!
C

 

So if the voltage of a lithium-ion battery drops below 3 volts, the battery will be ruined?

 

The Maximum Lifetime, and the most number of discharge/recharge-cycles,
are obtained by keeping the Batterie's Voltage between ~3-Volts and ~4-Volts.

Above or below these limits there will be "some" compromise in Battery-Life.

Newer-Cell-Phones now give You the Option of reducing
the maximum Charge-Voltage to extend the Batterie's Life-Expectancy,
at a small cost in Operating-Time between Charges.

This is very useful for Devices that stay plugged-in to a Charger most of their Life, like mine.
My new-to-Me, but outdated, Cell-Phone,
claims on the display that it will only charge to ~78% now,
but doesn't display a Voltage only a percentage..
.
.
.

 

The Maximum Lifetime, and the most number of discharge/recharge-cycles,
are obtained by keeping the Batterie's Voltage between ~3-Volts and ~4-Volts.

Above or below these limits there will be "some" compromise in Battery-Life.

Newer-Cell-Phones now give You the Option of reducing
the maximum Charge-Voltage to extend the Batterie's Life-Expectancy,
at a small cost in Operating-Time between Charges.

This is very useful for Devices that stay plugged-in to a Charger most of their Life, like mine.
My new-to-Me, but outdated, Cell-Phone,
claims on the display that it will only charge to ~78% now,
but doesn't display a Voltage only a percentage..
.
.
.

Hi L,
My hybrid car does just that. I can't even sit with the radio on without the engine start/stopping. Not good for a stake out
C

 

Hi L,
My hybrid car does just that. I can't even sit with the radio on without the engine start/stopping. Not good for a stake out
C

Um, I seriously doubt that sitting and listening to the radio will discharge your battery from 4V per cell to 3V per cell in less than a month or two. Sounds to me like it is trying to keep the battery fully charged all the time.

 

Um, I seriously doubt that sitting and listening to the radio will discharge your battery from 4V per cell to 3V per cell in less than a month or two. Sounds to me like it is trying to keep the battery fully charged all the time.

Hi B,
Under normal driving conditions the hybrid system is trying to keep the cells within a limited band for long life, it can be overriden, but a sign pops up to say damage can be done.
C

 

At the Limits .................
Quad-Copter, or Drone-Pilots, who compete in Races are the craziest people I've seen when it comes to Battery abuse.

They will Charge their Batteries to ~4.5-to-~4.6-Volts,
and, they may be running at ~2.5-Volts by the end of a ~5-minute-Race, intermittently pulling ~50-Amps or more.

This is so that they can run a smaller-physically-sized-Battery,
because to them, every Gram of weight could make the difference between Winning or Loosing the Race.
But ...........
they may get only ~5 Races out of a Battery, and then it's toast, and must be replaced.

It's Your Money.
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