How to Protect your Ultrabook's battery

Hi everyone, I'm new on this forum. I'm waiting for my Yoga 2 Pro to reach and before it reaches I really want to ask how should I protect it's battery for a longer lifespan. Any suggestions?

I've searched the net for solutions, and it's strange how some say charge it to 100% and never unplug it or charge it to 80% and discharge it to 10%. So many different suggestions yet I do not know which one is reliable. The battery on my previous laptop failed because I've always charged it without unplugging it so I wasn't sure about the suggestions posted on the internet.

Any suggestions guys?

 

The more you discharge and recharge the battery then the more you wear it out. However, the extent of the wear is greatest when recharging to 100% and discharging to empty.

If you use the computer mostly on mains power then just leave it plugged in as you did previously. Usually the BIOS will let the charge drop a few % before doing a top-up. If the Yoga comes with any utility to limit the maximum charge then reducing the maximum charge to 90% or 80% will be a further benefit provided you don't then end up fully draining the battery on the occasions when you use the computer away from the power outlet.

John

 

Ill repost something I posted earlier for someone else, the original question was regarding if constant laptop plugging reduces battery life.
Most of the information is still very valid for you.

OK, lets break down the factors that reduce the life of a battery:

1. Heat: The biggest factor, basically, for every 20 degrees of extra heat the battery is forced to operate in, you can permanently lose up to 10% (if the battery is at 40%) or 25% (if the battery is at 100%) of maximum charge. Too much heat and the battery essentially explodes.

2. Storage voltage: Batteries do not output a continuous voltage, a single cell usually has a nominal voltage of 3.85-4.3V (I.e. laptops tend to have multiples of these cells in series to deliver 12V, and several of these units in parallel in order to deliver the current required) from 50%-100% charge level. Cells that are forced to be stored at 4.3V degrade much faster than ones that are stored at 3.85V, you get double the number of recharge/discharge cycles for every .10V less the battery is stored at. This is the reason high quality, long lasting and continuous voltage batteries are so expensive and heavy, you literally have to overprovision on the number of cells. For example, an el-cheapo unit may only have banks of 3 cells in series to deliver 12V so thus the cells are forced to be stored at 100-110% (i.e max voltage), a high quality unit may use 4 or even 5 cells in series but each at a reduced voltage in order to deliver 12V so thus each cell is stored at well below 100%.You typically only see this kind of overprovisioning with medical units or other batteries that cannot be readily changed.

3. Discharge depth: batteries are typically rated on how many 100% discharge cycles are performed, the reason for this is that you get buildup at the anodes every time you discharge. Therefore, if you only discharge 50% and then you top up, you will roughly double you maximum number of discharge cycles.

4: Rate of charge/discharge: Fast/high current charging/discharge reduces the life of the battery, again this is because it encourages the buildup at the cathode/anode in addition to heat being produced. Heat accelerates buildup formation.

All these factors are synergistic.
Now back to the question, why does keeping it plugged in reduce the discharge cycles?. Assuming the battery in question has protection circuits which prevent over charging (this is practically mandatory with all Lithium Ion units to prevent fires).

1. People who plug in the laptop tend to use it for high performance applications. This produces a lot of heat which is then transferred to the battery. Heat reduces the life of the battery. A good laptop design would account for this and insulate the battery + isolate the CPU/GPU from the power delivery area. Ultrabooks, tablets and phones don't have this luxury of isolation so they tend to suffer this degradation the most, thankfully, manufacturers also tend to use the best possible cells for these applications.

2. Pretty much self explanatory, constant charging forces the battery to be stored at a high % thus higher voltage. This is where the recommendation, for 80% storage (presumably enforced by software) for normal applications and 40% for long life, came from.

3. Not very applicable for the issue of constant charging but it can play a role if the power delivery was poorly designed. Some manufacturers (cough, Acer, cough) grossly underspecc their Power delivery systems so under extreme stress, power is drawn from the battery to assist the power brick. Basically, in a plugged in scenario, the battery is continuously being charged and discharged, while this doesn't hurt too badly since the depth of discharge is small, the constant switching means the battery is continuously operating, this means heat is being produced internally. Heat is bad for Lithium Ion.

4. See number 3.

All of the above being said, most manufacturers do use high quality, well insulated cells with decent regulators for their OEM original units so it isn't as bad but the same standards don't apply to replacement/cheapo units. There is a reason why good quality units cost >$200.

So this hopefully cuts through some of the crap and misinformation out there.
Further reading from a very reliable academic source (most of my information was from here):
How to Prolong Lithium-based Batteries - Battery University

 

So what you mean is that :

1. In cases that I mostly use main plug, I should use the utility to enable maximum charge at 80% and just keep using the main plug without removing it.

2. In cases that I mostly use batteries, I can charge to 100% but shouldn't discharge it completely.

Am I correct?

 

What do you mean by 80% storage for normal applications and 40% for long life? I'm sorry since I'm pretty much a newbie in this.

 

@Marksman30k, according to what you say, do you agree with what John suggested in the #2 post?

 

He is correct.
Basically there are 2 mechanisms which will affect your charge as mentioned.

Battery longevity is rated typically according to the number of full discharge cycles (which is usually 300-500 for Lithium Polymer units in thin machines like yours)

Batteries are not constant voltage machines, they have a variable voltage according to their charge level. The longevity vs voltage curve of the battery peaks at usually around 80% capacity as this corresponds to the ideal voltage for storage while still maintaining a reasonable capacity for usage.
This is because high voltage (i.e. high charge level) encourages the rapid degradation of the battery cell leads. Typically, Lenovo laptops have always had a software function to limit the charge to this ideal 80% range for the maximum possible longevity for this reason.
The 40% charge level is typically used for extremely long term storage, this is what shops and warehouses do to store machines for months or years without losing battery longevity.

Because batteries are rated by a number of complete discharge/recharge cycles (the reason is that constant rapid charging or discharging encourages buildup at the battery leads) therefore, incomplete discharges where possible (e.g. discharge from 100%-50%) would increase the longevity inversely proportional to the discharge depth depth (by a factor of x2 for the example scenario of 50% discharge)

 

I accidentally partially unplugged the charger when I was running Windows memory diagnosis on a brand new Acer Travelmate a week ago.

I didn't notice until around an hour later, and then immediately stopped the diagnosis. The battery went from 80% (BIOS set, Windows thinks its 100%), to 27%.

HWmonitor reported that my battery had a 7% wear afterwards. Oops?


(Later Prime95 tests showed that the CPU temperature reached 66C under full load.)

 

Yes, that's a good summary of my advice.

Had you recently checked the wear? It might have been 7% already. If there was a change then the discharge / recharge cycle may have been enough to update the calibration.

John

 

With today's Li ion smart batteries, there's a lot less that you can do to mess it up.

 

I did not check HWmonitor before the "memory diagnosis on battery mode" mistake.

Also, I heard that in order to calibrate, you have to fully discharge. The battery only went down to 27% before I noticed the partially unplugged charger and panicked.

 

Full discharge is needed for a proper calibration so the system can find out when the battery is properly empty but I've noticed that substantial discharge can sometimes cause the battery's chip to update its wear value.

John