Still 99% charged?! (laptop charging question)

I have noticed lately that my battery meter on my laptop shows a steadily climbing % charge when charging the battery then it says 99% charged for a half-hour or more. Is it typical for this to occur? It's not a big issue but it just annoys me.

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Comments

skrpune

what kind of laptop do you have? If it's Lenovo you can use the Power Manager to check your battery health, and most other laptop manufacturers have some sort of built-in battery health meter application you can use to see if it's just not going to ever get back to 100%.

Forsaken_GA

Try letting it discharge all the way to the point where it dies, and then charging it back up to full.

exampasser

It's a Toshiba satellite a505-s6980 that I purchased in October. I'll try running the battery down again and charging it back up.

exampasser

My laptop just finished fully charging from 7%. It remained at 99% for 15 minutes so it did improve a significant amount.

exampasser

I just charged it up again from fully run down and it still sat at 99% for over 20 min. I guess this is just an issue with the Windows 7 battery meter needing to be more accurate but I'm not sure.

tiersten

exampasser wrote: »

I just charged it up again from fully run down and it still sat at 99% for over 20 min. I guess this is just an issue with the Windows 7 battery meter needing to be more accurate but I'm not sure.

The power management subsystem in Windows just queries the laptop charger circuitry and battery itself to see if it is charged. It doesn't make any guesses itself about whether the battery is 100% or not. If the battery doesn't report itself as being fully charged then Windows won't say it is 100%.

Charging a Lithium Ion/Polymer battery is complicated. It isn't a linear process where you apply X amount of voltage at Y current for Z amount of time and then at the end you get a fully charged battery. If you get it wrong then you can end up with at best a partially charged battery. If you get it really wrong then you've just gotten yourself a lithium fire and have fun with that.

A basic charging algorithm for a Lithium battery is 2 phases. The first phase is a constant current phase where you apply the rated maximum charge current until the battery reaches its maximum voltage. At this point the battery is only partially charged. The second phase is a constant voltage phase where you keep the voltage constant and keep charging until the charge current drops to some specified percentage of max. Only after you've done this is the battery fully charged.

Nearly all laptop batteries these days have a monitoring chip built into them that stores data on the the battery status. It knows the manufacturer, date of manufacture, design capacity, current max capacity, current capacity, number of discharge/charge cycles etc... The charger circuitry uses this data to charge the battery correctly. Sometimes the data is inaccurate due to various reasons and you need to do a full discharge/charge cycle once or twice to correct it.

exampasser

tiersten wrote: »

The power management subsystem in Windows just queries the laptop charger circuitry and battery itself to see if it is charged. It doesn't make any guesses itself about whether the battery is 100% or not. If the battery doesn't report itself as being fully charged then Windows won't say it is 100%.

Charging a Lithium Ion/Polymer battery is complicated. It isn't a linear process where you apply X amount of voltage at Y current for Z amount of time and then at the end you get a fully charged battery. If you get it wrong then you can end up with at best a partially charged battery. If you get it really wrong then you've just gotten yourself a lithium fire and have fun with that.

A basic charging algorithm for a Lithium battery is 2 phases. The first phase is a constant current phase where you apply the rated maximum charge current until the battery reaches its maximum voltage. At this point the battery is only partially charged. The second phase is a constant voltage phase where you keep the voltage constant and keep charging until the charge current drops to some specified percentage of max. Only after you've done this is the battery fully charged.

Nearly all laptop batteries these days have a monitoring chip built into them that stores data on the the battery status. It knows the manufacturer, date of manufacture, design capacity, current max capacity, current capacity, number of discharge/charge cycles etc... The charger circuitry uses this data to charge the battery correctly. Sometimes the data is inaccurate due to various reasons and you need to do a full discharge/charge cycle once or twice to correct it.

Ok thanks for the good in-depth explanation.

exampasser

I have cycled it twice now but it still has not fully corrected itself yet, but it has improved.

tiersten

exampasser wrote: »

I have cycled it twice now but it still has not fully corrected itself yet, but it has improved.

Do you know what is "normal" for that model laptop and that model battery?

Don't go crazy with the cycling though. You wear out a Lithium Ion/Polymer battery by using it. They're only rated for a specific number of full discharge/charge cycles before the usable capacity drops enough that you should replace the battery.

exampasser

tiersten wrote: »

Do you know what is "normal" for that model laptop and that model battery?

Don't go crazy with the cycling though. You wear out a Lithium Ion/Polymer battery by using it. They're only rated for a specific number of full discharge/charge cycles before the usable capacity drops enough that you should replace the battery.

I don't know what is "normal" for my Toshiba a505-s6980. This is my first laptop that I have ever owned. I'm not going crazy with the cycling though, its just being cycled though normal use. I just was wondering if this was normal in general for laptops to stay at 99% charged for a little while. Thanks for all of the help