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Laptop power

Community Veteran
Posts: 7,276
Thanks: 72
Fixes: 2
Registered: 30-08-2007

Laptop power

Since I took possession of my new laptop about last Novemberish, apart from once when I accidentally tripped over the lead it has never been disconnected from mains power. In the next few days I will be using the laptop on battery power alone. can I expect a) reduced battery life or b) reduced "on battery" time. Am I actually damaging the battery leaving it permanently plugged into the mains?
As far as I know the battery is the li-ion type.
I'd rather not get into a discussion about standby/global warming etc. and my contribution to same by leaving the laptop in this state. Have heard the arguments many times.
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
9 REPLIES
Community Veteran
Posts: 14,469
Registered: 30-07-2007

Re: Laptop power

Yes to both 1 & 2.
Over time, Li-Ion batteries will degrade but can be restored to almost full capacity by doing a full discharge then full recharge at least once a month.
So in your case, I would allow the laptop to fully discharge and then fully recharge a few times to get the best run time.
It's not good practice to leave it on mains power for extended periods of time.
Some laptops have a battery reconditioning function where it will discharge and the fully recharge while still running on mains. Check your battery power software to see if it has such a feature - my IBM Thinkpad does and I actually found it last week. Doing the discharge/recharge a few times in a row gained an additional 30 mins on-battery time (1.5hours -> 2 hours) for my Li-Ion having been using it for the past 2 years!
Just to add... the older NiCad type batteries will degrade when left on mains power for extended time and suffer 'memory loss' which it will loose charge capacity which cannot be recovered by discharge/recharge hence why Li-Ion is now used in laptops.
Note: Even Li-Ion batteries have a finite life... 3 -> 5 years is normally when it starts to degrade and needs replacing but it depends on how the battery is being used. More frequent discharges will extend the battery life.
Community Veteran
Posts: 14,469
Registered: 30-07-2007

Re: Laptop power

Community Veteran
Posts: 7,276
Thanks: 72
Fixes: 2
Registered: 30-08-2007

Re: Laptop power

Thank you Peter
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
James
Grafter
Posts: 21,036
Registered: 04-04-2007

Re: Laptop power

The battery on my Vaio has never lasted more than half an hour Sad
N/A

Re: Laptop power

Quote from: Peter
Yes to both 1 & 2.
Over time, Li-Ion batteries will degrade but can be restored to almost full capacity by doing a full discharge then full recharge at least once a month.
So in your case, I would allow the laptop to fully discharge and then fully recharge a few times to get the best run time.
It's not good practice to leave it on mains power for extended periods of time.
Some laptops have a battery reconditioning function where it will discharge and the fully recharge while still running on mains. Check your battery power software to see if it has such a feature - my IBM Thinkpad does and I actually found it last week. Doing the discharge/recharge a few times in a row gained an additional 30 mins on-battery time (1.5hours -> 2 hours) for my Li-Ion having been using it for the past 2 years!
Just to add... the older NiCad type batteries will degrade when left on mains power for extended time and suffer 'memory loss' which it will loose charge capacity which cannot be recovered by discharge/recharge hence why Li-Ion is now used in laptops.
Note: Even Li-Ion batteries have a finite life... 3 -> 5 years is normally when it starts to degrade and needs replacing but it depends on how the battery is being used. More frequent discharges will extend the battery life.


Not strictly true Peter (right answer, wrong reasons - kinda),
Li-Ion batteries do not suffer from the same memory effect (80% of original capacity should be achievable for the first 500 charge cycles), and are not impacted directly by being left on permanent charge, nor from multiple charges/discharges to the same extent that Ni-Cad cells were (there is a small 'memory effect'). 
The capacity of Li-ion battery degrades constantly from the time it is manufactured.
This degradation is increased at higher temperatures (hence it is true that leaving the notebook on charge constantly will have likely reduced the useful capacity of the batteries more than it would had the batteries been removed and stored somewhere cool)
The fully-discharge/recharge cycle was/is recommended for Ni-Cad cells to avoid/negate the memory effect. A similar procedure is recommended every 30-40 charging cycles on a Li-Ion cell, but for different reasons (albeit with similar outcomes)
Li-Ion cells contain circuits which measure the power remaining in the cell, so they can cut power when the cell gets down to around 20% capacity (this is because Li-Ion cells can't be recharged if they go completely flat, whereas Ni-Cad cells could be)
The discharge and recharge cycle is an attempt to ensure that the 'power off' circuitry is properly reset so that it correctly reports the 20% stage, and doesn't report it earlier - resulting in an apparent shorter battery life.

So, still Yes to both 1&2  Cool
Community Veteran
Posts: 7,276
Thanks: 72
Fixes: 2
Registered: 30-08-2007

Re: Laptop power

Many thanks for the concise explanation James.
It seems my HP laptop doesn't have a discharge option (at least I haven't found one yet) so the best to do is let it run down from time to time?
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
N/A

Re: Laptop power

Yeah, just remove the mains power, and use the machine till it shuts itself down (If you want to achieve this quickly, you could watch a DVD, battery would probably be flat before the movie ended, or not long after!)
Then reconnect the mains and let the cells recharge fully.
Theoretically, Li-Ion cells *can* be fully charged in about 45 mins, but its better to go for a few hours or overnight if you can.
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: Laptop power

ive just had to send my battery back to dixons group bought laptop from currys. any way i didnt know that when u run your laptop off the mains you can take the battery out so its not allways charging. well luckly just before the the year warrnty was up (3 days) windows bat meter was allways on 3% and would not take any charge. so sent it of to dixons group a currier came and picked it up well that was a month ago now rang them up 2 weeks ago and said they had lost it and i should of accutally sent the whole laptop ( r they serious or what they have lost my battery as it is) well fesw more angry calls saying im recordeding this phone call for the oft and i might get a my battery back or a new one.
Any ways ive learnt that its best to fully charge your battery and if your runing of the mains to take your battery out and you should get about 3-4 years out your battery
Community Veteran
Posts: 7,276
Thanks: 72
Fixes: 2
Registered: 30-08-2007

Re: Laptop power

Doh!! After all this time and with using 4 laptops between my wife and I, it never even occurred to me to use them with the batteries removed.
Thank you scootie.
Not only does it extend the life of the battery (simply because in our case we don't use it) it's a lot more comfortable on the "lap" when used that way, because of the heat of the battery (especially in the summer...a constant complaint from my wife)
Only downside I can see is the possibility of dust ingress to the battery terminals, as in both our cases (HP and Toshiba) the battery and cover are moulded together, might try a strip of insulating tape over the computer side terminals.
So in our case now it's which will last longest...the computer or the battery? I'm not taking any bets on the computer!!
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.