Latop Battery at 100%

[bukuxx]

Do laptops actually charge up to 100% (storing capacity) or do they just stop charging at somewhere close to 100% to avoid overcharge for their batteries.

Hence, which power do they use once it shows "Fully Charged"? Do they use the battery's power and it just keeps recharging at a very low rate at the same rate as it discharge whisle we use it? OR are we actually using the power from the main power that supplied from our great wall plug?

Jokes asidee......

Anyways, let me kindly emphasis the main four things that I really want to ask:
1) Do laptops actually charge all the way to 100%?
2) Do the 'charging' stop charging once it says 'fully charge' (to avoid overcharge overtime i.e; leave it plugged in over night)
3) When fully charged is shown and the laptop is plugged in, which power do we use? Is it its battery discharging at a row rate and charging at the same time to keep it stay-still at 100%? Hence it means we only use the battery's power only when we it isn't plugged in to the AC Or are we using the power from the plugged-in power?
4) Do they Automatically switch the current inflow from the AC adapter to the battery once it's full charged? (i.e leaving it plugged in overnight)

Sorry for long post but I am really curious about this and been having a bit of argument with my friends with these topics.

 

[BFG-9000]

You'll have to define what you mean by 100% but in general, Li-Ion should go 2500 cycles from 4.1 to 2.5v each time. Charging to 4.2v still nets 750 cycles, and 4.25v drops it to 400 cycles. 4.3v is inadvisable as it drops below 200 cycles life. Each bump of 0.1v charge adds ~15% to capacity. Lifetime is to 20% permanent loss of capacity.

Most consumer goods do in fact charge to 100% of their design charge in order to maximize useful charge and because such items are intended to be obsolete in two years. If they did not stop charging there they would catch on fire, but batteries last longer if not always stored at 100%. My laptops are plugged in all of the time and seem to not kick in the charger until charge has dropped to around 90%--they use AC and switch to battery immediately if unplugged, like a built-in uninterruptible power supply.

The major exception is hybrid cars which only charge to around 80% and discharge to 20% so design life of the battery pack will be well over 10 years.

 

[bukuxx]

You'll have to define what you mean by 100% but in general, Li-Ion should go 2500 cycles from 4.1 to 2.5v each time. Charging to 4.2v still nets 750 cycles, and 4.25v drops it to 400 cycles. 4.3v is inadvisable as it drops below 200 cycles life. Each bump of 0.1v charge adds ~15% to capacity. Lifetime is to 20% permanent loss of capacity.

Most consumer goods do in fact charge to 100% of their design charge in order to maximize useful charge and because such items are intended to be obsolete in two years. If they did not stop charging there they would catch on fire, but batteries last longer if not always stored at 100%. My laptops are plugged in all of the time and seem to not kick in the charger until charge has dropped to around 90%--they use AC and switch to battery immediately if unplugged, like a built-in uninterruptible power supply.

The major exception is hybrid cars which only charge to around 80% and discharge to 20% so design life of the battery pack will be well over 10 years.

Dear BFG-9000
First I want to let you know that I have very low knowledge base about batteries and how they work. Hence I have no clue about what you mean By >>Li-Ion should go 2500 cycles from 4.1 to 2.5v each time. Charging to 4.2v still nets 750 cycles, and 4.25v drops it to 400 cycles. 4.3v is inadvisable as it drops below 200 cycles life. Each bump of 0.1v charge adds ~15% to capacity. Lifetime is to 20% permanent loss of capacity.<< Please explain in a more understandable language please.

Second: By 100% I mean " http://prntscr.com/ealrww " *please-do-see-it*

Third: Did you just mention that most batteries are intended to only last with its best performance for only two years? OR DIE AT ALLL?? Please explain that part too, because you're making me feeling a bit insecure with all the batteries I am having around me right now (they all are over two years old :| ) and THEY WOULD CATCH ON FIREE? :-O

Fourth: So by your anecdote, you also answer answer my 3rd question that laptop power uses its own batteries once fully charged until the battery drops to around 90%?

Thanks for the reply. Let's keep it bump! 😉

 

[BFG-9000]

The maximum voltage per cell when fully charged, and the depth of total discharge before shutdown are the two primary things that affect the life of a Li-Ion battery. Neither are things that you can change as they are designed-in by the engineers who balanced runtime vs. lifespan. Every time they screwed up and made batteries catch on fire it's a big deal and made the news.

Yes, it is perfectly normal with consumer devices for the Li-Ion battery to degrade in a short time. You may have read in the news 14 years ago that Apple lost a class-action lawsuit because their non-replaceable iPod batteries degraded in 18 months until they didn't last as long as claimed. Did they make the battery replaceable? No, they just stopped claiming how long the battery lasts and still expect you to buy a new iPhone every two years.

Admittedly, Li-Ion has improved since then and now 3 years is the typical life to 80% capacity (note the voltage still reads 100% when fully charged but runtime is down to 80% of new). And Li-Ion tends to degrade very gracefully so is still usable only with ever shorter runtime per charge--even if your phone only runs half as long as when it was new it is still useful. The Nissan Leaf loses 27.5% in just 1-2 years, which is bad because it starts at only 73mi claimed range, and is why it has the lowest resale value of any car.

Perhaps these nice charts over at Battery University would be easier to understand.

 

[bukuxx]

The maximum voltage per cell when fully charged, and the depth of total discharge before shutdown are the two primary things that affect the life of a Li-Ion battery. Neither are things that you can change as they are designed-in by the engineers who balanced runtime vs. lifespan. Every time they screwed up and made batteries catch on fire it's a big deal and made the news.

Yes, it is perfectly normal with consumer devices for the Li-Ion battery to degrade in a short time. You may have read in the news 14 years ago that Apple lost a class-action lawsuit because their non-replaceable iPod batteries degraded in 18 months until they didn't last as long as claimed. Did they make the battery replaceable? No, they just stopped claiming how long the battery lasts and still expect you to buy a new iPhone every two years.

Admittedly, Li-Ion has improved since then and now 3 years is the typical life to 80% capacity (note the voltage still reads 100% when fully charged but runtime is down to 80% of new). And Li-Ion tends to degrade very gracefully so is still usable only with ever shorter runtime per charge--even if your phone only runs half as long as when it was new it is still useful. The Nissan Leaf loses 27.5% in just 1-2 years, which is bad because it starts at only 73mi claimed range, and is why it has the lowest resale value of any car.

Perhaps these nice charts over at Battery University would be easier to understand.

Sorry BFG but I honestly still don't understand what the meaning of 'the maximum voltage per cell when fully charged, and the depth of total discharge before shutdown'. Maybe by understanding of batteries is really that low. 🙁 Anyways I am trying to understand also what you meant by 'typical life to 80% capacity'. Does that mean the batteries eventually reduce their life to around 80% capacity (but we know its display will still work the same way as charging, out of battery, and charging, and full charge at 100%). BUT THE LIFE IS ACTUALLY DEGRADES ITSELF TO 80% CAPACITY RIGHT?

 

[BFG-9000]

Yes the runtime will drop to 80% of when the battery was new but the dumb charge indicator will still say 100% when fully charged. As it measures only voltage it is saying you have 100% of that 80% capacity available so it's not lying (unlike some cellphone signal strength indicators). It's just showing you what's left in the "active area" here:

They show the dead area has turned into rocks
The traditional analogy is if electricity is like water, voltage is pressure and current is flow rate.

 

[bukuxx]

how about my question 2/4 and 3?
*2 and 4 are pretty much the same questions*

 

[BFG-9000]

I thought it was pretty clear when I said that if the charger ever didn't shut off at full charge, the battery would catch on fire (or the battery would blow its protection circuit). It is possible to make a charger that drops to a low trickle-charge but the main charging circuit always shuts off at 100%, or you would be reading about it in the news.

As I said, this laptop is plugged in all of the time and it is currently at 92% and not charging, so obviously the charging completely turns off by itself. If I unplug the charger (the laptop is on) and plug it back in, it starts charging so clearly the laptop normally runs on AC so long as it is plugged in, but can also run the laptop and charge at the same time if needed. If I just continue to use the laptop until the battery drains below 90%, the charger automatically kicks on whether the laptop is on or not.

The battery is slowly draining over a month or two not because the AC adapter isn't sufficient to run the laptop by itself (you've seen it can charge the battery at the same time), but because any batteries with protection circuits always are slowly draining themselves in something called self-discharge. The laptop never draws from the battery when plugged into AC.

So the engineer(s) who designed this Dell decided against any trickle-charge to prolong the lifespan of the battery (I did mention earlier that storing at a lower charge level slows degradation), even though this means if I have to unplug it and go, the charge may be as low as 90%. The engineer responsible for your laptop may have chosen different.

 

[bukuxx]

I thought it was pretty clear when I said that if the charger ever didn't shut off at full charge, the battery would catch on fire (or the battery would blow its protection circuit). It is possible to make a charger that drops to a low trickle-charge but the main charging circuit always shuts off at 100%, or you would be reading about it in the news.

As I said, this laptop is plugged in all of the time and it is currently at 92% and not charging, so obviously the charging completely turns off by itself. If I unplug the charger (the laptop is on) and plug it back in, it starts charging so clearly the laptop normally runs on AC so long as it is plugged in, but can also run the laptop and charge at the same time if needed. If I just continue to use the laptop until the battery drains below 90%, the charger automatically kicks on whether the laptop is on or not.

The battery is slowly draining over a month or two not because the AC adapter isn't sufficient to run the laptop by itself (you've seen it can charge the battery at the same time), but because any batteries with protection circuits always are slowly draining themselves in something called self-discharge. The laptop never draws from the battery when plugged into AC.

So the engineer(s) who designed this Dell decided against any trickle-charge to prolong the lifespan of the battery (I did mention earlier that storing at a lower charge level slows degradation), even though this means if I have to unplug it and go, the charge may be as low as 90%. The engineer responsible for your laptop may have chosen different.

Thanks for taking time mentioning my question 2/4 again as requested. My apology for did not pick it up earlier the answer.
Though I now well understood about the charging and which power it uses. But I highly HIGHLY doubt that this would ONLY work for Dell? I am using an acer replying to you right now and it's been plugged in fully charged at 100% for hours. it has never gone switched off by itself (no matter if the laptop is on or not, it would keep the charging light on forever if I have it plugged in given it tells me if it's fully charged or not *BLUE LIGHT* or charging *RED LIGHT" OR Critical Battery below certain percentage, 20% *flashing red light on and off*).
My friend on the other hand has a Dell XPS 15 and he comments that his laptop would always use AC as long as it's plugged in and always ALWAYS automatically switch the charging adapter off once its fully charged (this is talking about when he leaves his laptop plugged in all night long).
Same scenario happens to his other Dell Inspiron 1122 M102z. He would always leave it plugged in all night because he's assured that it would switch off by itself once it's fully charged. Unlike my acer and my other other friend's acer. Our acer never switched its charging off like Dell, so I assume this (what happens to you and to my friend's dell) only works on Dell?