charging percentage, capacity, and extending cell phone battery life

[markr6]

The iPhone has Low Power Mode, available in Settings - Battery, which doesn't allow anything to run in the background and shuts off visual effects. It won't even check for mail unless you open the app.

Thanks. I remember that coming up automatically when the battery hit 20% but never really knew what it did.

 

[Capolini]

I have come to a realization that ACCEPTANCE is the key!

I lost 10% capacity in the first 1h 40m today! Sent one text and looked at One email!,,,I know,,all the stuff going on even though I am not using it!!

Since I work part time I have plenty of time to charge it! So if it gets close to 40% before dinner time I will just charge it!! Last night @ 9:30pm after my hike w/ CAPO it was at 45%.So it made it!

Mine charges fast,,,1940 mAh battery. It only takes an hour at the most when it is at 30/40% capacity until a full charge,,,,,my charger is 1A.

 

[StarHalo]

I have come to a realization that ACCEPTANCE is the key!

Chargers everywhere is the key - the cord right there on the nightstand, the multi-port charger in the car (four seats for four adults = four USB ports,) a battery pack that's ready to go if you need to charge in a less convenient place (the dinner table, outside, during a power outage,) a battery case for the long family outing, etc.

Be aware that leaving the battery at a low charge percentage is like driving around with your fuel tank nearly empty; fate doesn't always need to be tempted..

 

[terjee]

Be aware that leaving the battery at a low charge percentage is like driving around with your fuel tank nearly empty; fate doesn't always need to be tempted..

For LiIon, that's not just true, but the car is also leaking gasoline (self discharge), and prone to explosions later in life, if the fuel tank is ever empty. Even if you fill it and generally care for it later on.

 

[markr6]

Be aware that leaving the battery at a low charge percentage is like driving around with your fuel tank nearly empty; fate doesn't always need to be tempted..

Every time I get in my wife's car it says something like "53 miles to empty"...basically touching the red line. Drives me crazy!! Man, I'm really throwing her under the bus in this thread

 

[Gauss163]

I have a economy Asus phone that shows battery charge %
When charging it, it takes about 2 minutes of charging to raise the percent charge 1%. (I am rounding numbers)
But when it gets to about 90% charged, it takes longer, maybe 4 minutes for each 1% increase in charge.

Li-ion cells are charged using a CC/CV (Constant Current, Constant Voltage) algorithm where the current tapers off at the end when the cell reaches the target charge voltage. This implies that the capacity will increase much slower near the end of charge because the current is much lower than it was at the start of charge (about 1/10 or 1/20 near the end). Also newer phones may incorporate various fast-charging tweaks to CC/CV, which may increase that factor even further.

Please give me a strategy to extend/maximize the battery life. It doesn't have a replaceable battery. I'm thinking that it is better to NOT fully charge it, but rather stop at about 90%.

Yes, that's one way to prolong life. Generally the more time the cell spends close to 50% capacity the longer the life you will get. For example, studies show that if you only use it between 90-10% capacity you'll get a significant increase in life vs. 100-0% (i.e. full charge and full discharge). More extremely, if you only used it between 60-40% capacity you could get between 5-10x the life. But of course that is not practical. Generally the rule of thumb is that to maximize life one should minimize the time that the cell spends at extreme voltages and temperatures (which accelerate internal parasitic reactions and other degradation processes).

 

[terjee]

More extremely, if you only used it between 60-40% capacity you could get between 5-10x the life. But of course that is not practical.

I do agree with your point – not complaining – but there's a subtle difference that's important to note:

The findings typically don't state 5-10x the battery life, but 5-10x the cycle count. That subtle difference is very important. If you only move the state of charge 10 percentage points, compared to 80 percentage points, you'd also *need* 8 times the number of cycles, to extract the same amount of energy from the battery. That quickly obliterates any significant gain. These things do matter at an industrial scale. If things work out to 4x the lifetime if you have 2x the batteries, because you can keep the batteries at more comfortable states of charge, that could be quite significant. For consumer electronics though, if often doesn't make too much sense to try to optimise like that.

It can even be doing more harm than good. If you charge only to 70%, that would significantly increase the chances of a deeper discharge, and you're hurting more than gaining.

It's easy to overestimate the potential gain, and underestimate both the potential harm, and the potential work to get it all done.

By all means, if it's convenient to do so, store a cell at 3.92V rather than fully charged, and please don't deep discharge, but there's no need to keep a close eye at a charger to stop charging at exactly the "magical" moment, or go to extremes like that.

 

[Poppy]

I do agree with your point – not complaining – but there's a subtle difference that's important to note:

The findings typically don't state 5-10x the battery life, but 5-10x the cycle count. That subtle difference is very important. If you only move the state of charge 10 percentage points, compared to 80 percentage points, you'd also *need* 8 times the number of cycles, to extract the same amount of energy from the battery. That quickly obliterates any significant gain.
<SNIP>

terjee,
I noticed the same thing in "cycle count".
What drives me crazy is that people do not write perfectly clearly, and often leave one to wonder.

In this instance the question is: How do they define "cycle count"?
Typically, One cycle count is a fully charged battery, fully discharged, and then fully re-charged is ONE cycle count.

The extraordinary gains in cycle count claimed, makes one wonder are they defining a cycle as any partial recharge? If so, that makes the data presented meaningless, and the study worthless.

 

[Gauss163]

I do agree with your point – not complaining – but there's a subtle difference that's important to note: The findings typically don't state 5-10x the battery life, but 5-10x the cycle count [...]

Not true. I refer to lifetime cumulative energy which, of course, accounts for variations in cycle size.

 

[TinderBox (UK)]

We need good colour e-ink that can handle video, and you only refresh the pixels you need too not the whole display, e-ink displays use very little power, and 95% of the time the display is mostly static so no power is used, you have to have some sort of led backlight, kindles backlight have a 2 month battery life at 30min a day, so we should be able to get a week.

Also when will manufactures stop making phones thinner and put a decent capacity battery inside.

My HTC M7 is 3 years old and the battery is still great (It`s the worst phone in the world too have to change the battery), I have only ever charged it to 80% and never discharge it below 20%, I use GSam battery monitor to give an alarm on charge and discharge level.

John.

 

[Gauss163]

I noticed the same thing in "cycle count". hat drives me crazy is that people do not write perfectly clearly, and often leave one to wonder [...]

Such studies usually measure in terms of "equivalent full cycles", e.g. 2 discharges of 50% capacity (DOD) are counted as equivalent to 1 full cycle, as are 4x 25% discharges, etc.

It is not so well-known that Li-ion cells behave very differently than lead-acid cells when it comes to partial discharges. Namely they are much more sensitive to the depth of the discharge, and to the region in which it occurs. Generally, discharges that are lower depth, and more balanced around 50% capacity will prolong lifetime - possibly by large amounts.

Below is an example from Energies 2016, 9(1),12; doi:10.3390/en9010012, E. Telaretti et al. Here DOD means Depth Of Discharge. So a 25% DOD means a discharge of 1/4 of the capacity of the cell.

The prior table shows that decreasing the discharge depth from 80% vs. 20% yields 4.2 times the lifetime (10000 vs. 2400 cycles) for their Li-ion cells. But the corresponding lead acid gains are much smaller, about 1.2 times the life.

There are more precise studies, e.g. the graph below, from Ecker et al. Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries, Jnl Power Sources 248 (2014) 15, 839-51, which shows the dependence on both the depth of discharge and its distance from center = 50% SOC (here SOC = State Of Charge, e.g. 50% S0C means 50% of capacity, i.e. half full).

The leftmost column of data points are for very short discharge cycles of depth 5% (of capacity). The lowest 2 points (green and brown overlapping points) at (x,y) = (5%,2000) show that they obtained the equivalent of about 2000 full cycles when the discharge was centered at 75% SOC (green curve) and 90% SOC (brown curve). Moving up to the blue point at about 5800 we see that they got almost 3x as many full cycles by shifting the discharge center point to 25% SOC, i.e. one-fourth capacity. The topmost purple point shows they got about 8500 full cycles by shifting the center of discharge to 50% SOC. So shifting the discharge center point to 50% SOC (vs. 75% or 90%) yields more than a factor of four (4.3) times increase in the number of full cycles, i.e. 8500 vs. 2000 full cycles. This shows how balancing discharges around 50% SOC may yield large gains in life. Similar remarks hold for the next two columns of points representing discharges of depth 10% and 20%.

The rightmost purple data point corresponds to full discharges (100% DOD). They yield under 500 full cycles, more than 17 times fewer than the 8500 equivalent full cycles obtained at 5% DOD centered at 50%.

 

[Poppy]

Thanks Gauss163,
That was very helpful.

 

[TinderBox (UK)]

20% DOD for 10000 cycles, not if you go from 100% to 80% then charge back to 100%, hitting 100% every time shortens the battery life, now 40% to 60% would be more like it, but who can get a day on their phone and only use 20% of the battery.

What DOD is used on satellite battery packs, when it can be virtually impossible to replace them, so you need them to last as long as possible.

John.

 

[Gauss163]

duplicate

 

[Gauss163]

20% DOD for 10000 cycles, not if you go from 100% to 80% then charge back to 100%, hitting 100% every time shortens the battery life, now 40% to 60% would be more like it, but who can get a day on their phone and only use 20% of the battery.

Yes, the study shows that the longest life is obtained when discharges are centered around 50% capacity (and are shallow), and worst when they are centered at extreme voltages (near full or near empty). This yields evidence supporting the general rule of thumb that I often mention: to maximize health one should minimize time the cell spends at extreme voltages (and temperatures). Keeping (dis)charges shallow and centered around 50% is one way to help minimize the time the cell spends at extreme voltages.

What DOD is used on satellite battery packs, when it can be virtually impossible to replace them, so you need them to last as long as possible.

Most likely they do exploit such properties in order to increase lifetime. Though shallow, centered (dis)charging regimes are inconvenient to execute manually, they are easy to automate.

In summary, raise your cells opposite your children: keep them shallow and self-centered to give them the best possible life.

 

[herektir]

I have an iphone se that i have the power saver mode on (no apps checking online all the time for updates etc), locations services off unless app requiring it is open, cellular data off, and shut off anything else i dont need 24/7. Doing these things essentially makes it just a phone with a camera untill i go in and turn things on. I charge to roughly 90-100%, let discharge to about 30% and depending on usage, so one charge lasts 3 to 6 days. A 100% to 10% would last a week.

Generally that means i get say 1 full charge cycle every 5 days for roughly 75 cycles a year. I generally use a phone i buy for 3 to 4 years and with nonreplaceable batteries like an iphone, i want it to last. The replaced phone i keep as a backup for just in cases like 911 or breakage of the new one, keeping a roughly 40% charge on it. My 2nd previous phone, a feature phone that i gave to my dad, held a decent charge for 3 to 5 days for him least up till last year despite it being 8 or 9 years old with use not just standby time. Real main reason for doing this is im not made of money, i dont need a new phone every year or 2, and lets me save some money for the flashlights i like.

 

[markr6]

I just upgraded my iPhone 6-64GB to a 6S-128GB. Basically for free since the price at verizon is what ebay gave me for my old one straight up. I didn't like what they did with the iphone 7, so I figured I would get a 6S while they lasted, twice the space, and a fresh battery.

Even though I took care of the battery, I can already tell the difference. I obviously did some damage to my old phone by backpacking in 0°F weather. I had it in my pocket, but it was still pretty cold. It never seemed to recover from those few cold trips.

 

[eh4]

To me it's a balancing act between keeping the battery healthy and not wearing out the micro USB port.
I'm excited that wireless charging is becoming a more common feature, too bad it's not more efficient.
I'm trying to rely on wireless charging for frequent, day to day sedentary charging, and save the micro USB port for mobile charging with external batteries.

 

[TinderBox (UK)]

Just buy one of those magnetic microusb adapters, I have one on my tablet and they are great, no more wear one the microusb port, there are lots of different brands and plug sizes (if you have a case make sure it fits) the link below is just an example i am not recommending it.

https://www.amazon.com/dp/B00YH0CCQE/?tag=cpf0b6-20

John.

To me it's a balancing act between keeping the battery healthy and not wearing out the micro USB port.
I'm excited that wireless charging is becoming a more common feature, too bad it's not more efficient.
I'm trying to rely on wireless charging for frequent, day to day sedentary charging, and save the micro USB port for mobile charging with external batteries.

 

[eh4]

Wow!
Very nice, actually I was rolling around in my head how to design almost exactly that product. -though I was thinking no magnet in the micro USB adapter itself to prevent metal and magnetite dust from accumulating, and rely on different sized pos and negative to prevent reverse polarity. Also no data pins, just charging.
This is neat though, I'm going to order one model or another and check it out. Thanks!