Solved How to discharge a laptop battery?

July 16, 2012 at 09:25:39
Specs: Windows 7
Normal procedure to maintain laptop battery health.

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July 16, 2012 at 09:37:43
✔ Best Answer
Don't discharge it fully. That's the surest way to kill a battery. And don't keep it on charge when it is fully charged.

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July 16, 2012 at 09:40:57
Todays laptops use Lithium Ion battery technology. They are very different from NiCad and Nickel Metal Hydride technology of the old days where it was suggested to discharge the battery all the way before charging to keep the battery from getting a memory so to speak and only being able to charge partially.

There is nothing your really need to do to maintain a litium ion battery. Laptop manufactures do suggest letting the battery run down all the way occaisionaly to calibrate the charging cicuit but it does nothing to maintain the health of the battery.

ijack, there is nothing wrong with running the battery all the way down. The only technology that does not like being drained fully is lead acid batteries and they don't use those in laptops. It does not hurt to keep the charger on when fully charged. Charging circuits know when the battery is charged and shuts off charging to the battery.

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July 16, 2012 at 10:14:27
The only safe way to discharge a battery may be to do it under a normal load. I doubt you need to do this.There is no reason to discharge a battery to maintain health. At one time it was believed that one could get a memory in Ni-Cad. I doubt you have a ni-cad.

If you believe the car makers who are trying to maintain the lithium ion and advanced batteries then do not ever reduce them beyond 70% full.

A new type battery would suffer deep cycles, many charges and from time. All of those cause a battery to go bad. Just use it normally and when it goes bad get a new one.

Google is evil

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Related Solutions

July 16, 2012 at 10:40:52
I'll refer you to for advice on fully discharging a battery (don't do it!). As for leaving it on charge - i prefer not to rely on the efficiency of the charging circuit; it may stop charging or it may not. If I disconnect when fully charged then I control the situation.

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July 16, 2012 at 12:55:54
Yes I read the part where it says you will get less cycles if you fully discharge it and not to do it, but you still get the same lifetime output capacity. And then they go on to totally contradict themselves.

Lets say a battery can charge and discharge 1000 times. So a full discharge of 100% will let you recharge 1000 times. If you only discharge to 50%, you can charge it 2000 times, discharge to 10% and recharge it 10,000 times. It's still all the same output and capacity percentage.

Look at the chart they provided

100% DoD 300 – 500

50% DoD 1,200 – 1,500

25% DoD 2,000 – 2,500

10% DoD 3,750 – 4,700

Do you see how it pretty much adds up to the same output?

And if it was damaging, why would Apple and other laptop/tablet manufactures suggest doing it once a month?

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July 16, 2012 at 14:24:42
I think you are confusing 10% charge with "fully discharge".

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July 16, 2012 at 14:31:26
IBM had some trouble with their batteries. They send out letters to owners that said basically this. If you use your laptop as a mobile computer then leave the battery in all the time. If you use the laptop as a desktop then take the battery out.

No matter what you do the battery will go bad.

Google is evil

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July 16, 2012 at 15:03:16
"I think you are confusing 10% charge with "fully discharge""

I'm not sure what you mean. All the information I posted is based on it being fully recharged to 100% after any given dischage percentage.

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July 16, 2012 at 16:01:47
In summary:
The only safe way to fully discharge your battery is to use it in the laptop.
To run it until the laptop shuts down by itself is not a good idea for the laptop and any files you may have had open.
It is not needed to run down Lithium batteries fully as with older NiCad rechargable batteries
I still recommend running your laptop batteries down until you get a low battery warning, at least occasionally.
I still recommend removing the charger when the battery is fully charged or in the morning when plugging it in at night.
If you have an important reason for needing a full charge, then even if it is 50% or more charged, charge it. If you do not, then wait until it goes down before charging it.
Use common sense, if power is going through the battery (charging circuit is not stopping it) then you are loosing electrolyte so charge it when you need to, but not all of the time.
Also, if you always plug in your laptop, you are inserting the plug into the jack more often, if the charge jack or charge plug are going to wear out or loosen up, it will then happen sooner and you will be in for a costly repair if you need to replace the charging jack on the laptop.

You have to be a little bit crazy to keep you from going insane.

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July 17, 2012 at 00:00:12
@THX. In your reply #5 as well as misunderstanding the difference between a partial discharge (say to 10 %), which is fine, and a full discharge (say to 1% or less), which physically damages the battery I believe you also misunderstand the meaning of "cycle". A cycle means a discharge from 100% to nearly full discharge. So, for example, a discharge from 100% to 50% is only half a cycle, from 75% to 50% is a quarter of a cycle, etc. . When the article says that the number of cycles is reduced it means that the total output lifetime of the battery decreases.

Even discharging to 10%, rather than fully discharging, can be dangerous. If the battery is left in this state it will soon lose its remaining charge and drop below the threshold at which permanent change occurs. The advice that some manufacturers give of a near full discharge (followed by an immediate recharge) is not to prolong the battery life but to recalibrate the remaining time counter. The immediate recharge is essential.

The advice given by Fingers in #9 is excellent.

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July 17, 2012 at 08:04:38
ijack, I worked as a technician at a battery manufacturing plant for 9 years, I am aware of what a cycle is.

Everything you describe is relating to old NiCad ot nickel metal hydride technology. Leaving a lithium ion battery battery in a semi discharged state will not cause the battery to loose the remaining charge, nor is it damaging.

"The advice that some manufacturers give of a near full discharge (followed by an immediate recharge) is not to prolong the battery life but to recalibrate the remaining time counter"

Yes, I know, I stated that in my first post.

And technically you can't fully discharge a litium ion battery. The battery pack itself has monitoring circuits in it and will shut the pack off when it reached a certain level of discharge so it can't ruin the battery.

Yes, the advice Fingers gave was excellent, he even restated a couple of points I had made.

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July 17, 2012 at 09:03:47
In all the new cars the use advanced batteries they have tried to never let the bank get below about 70% of charge. They also never let the pack get to a full charge.

The problem is each maker of batteries have their own chemical if not different chemistry. Not two batteries will act the same.

Just use it. It will go bad on it's own. If you don't need to have it in then take it out.

Google is evil

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July 17, 2012 at 09:24:43

See page 2 - Avoid very deep discharges.

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July 17, 2012 at 10:16:07
A quote from that page

"Most Li-ion batteries have protection circuitry within their battery packs that open the battery connection if the battery voltage is less than 2.5 V or exceeds 4.3 V"

As I also stated in post #11, battery packs have monitoring circuits that will shut the pack off at a certain level. You keep posting information that say exactly what I've been saying all along.

Can we just end this, The bottom line is most laptop and tablet manufactures suggest discharge all the way occaisionally to calibrate the charging circuit. They wouldn't recommend this if it were going to damage the battery, which it doesn't. There is protection in place.

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