When to charge?

[marty1990]

Okay this will be my last battery question.... I hope.

There might be threads regarding the battery and when to charge, but am wondering whether this is a good rule of thumb.

From 100% use my iPad. When it gets to 15% charge it, not necessarily to 100%, but never letting it deplete to less than 15%. So basically charge it as and when but not lower than 15%. And then once a month, deplete the battery completely and do a full charge to calibrate the battery percentage?

 

[charlieegan3]

sounds like you've got it pretty much sorted to me.

I wish your battery a long an healthy life!

 

[silverblack]

Yes, but only if you want to win a prize in battery maintenance.

I'd rather enjoy my iPad and charge it whenever it’s convenient. After 2 years, my battery may (or may not) last a few minutes shorter. But it only matters if I do need to run my iPad to the last electrons, which very rarely happens... Why? Remember? I already charged my iPad earlier when I had a chance

Oh, BTW there is a good chance I'm on iPad 4 two years from now.

 

[JMG]

Yes, unless you plan on keeping the iPad for 5 years I would just let all the stress go and not even think about the battery.

 

[PlaceofDis]

i used to worry about properly taking care of the battery, but then i realized that just using the iPad/iPhone etc how i need to is more important than bending over backwards to make sure i adhere to some strict guidelines i set for myself. the battery technology is improving and it shows

 

[gnasher729]

And then once a month, deplete the battery completely and do a full charge to calibrate the battery percentage?

You don't _need_ to calibrate the battery. It doesn't improve battery life at all. The only thing it does is making the display more accurate. So a fully charged, uncalibrated iPad might display "94%" and last for 8 hours 37 minutes, while a fully charged, calibrated iPad would display "100%" and last exactly the same 8 hours and 37 minutes.

 

[Jackintosh]

I've heard that depleting the battery all the way down to zero is not all that healthy (for the battery, that is). Although good for calibration.

 

[silverblack]

Here's what I do. Turn off that damn battery % meter, and get on with your life.

 

[Big-TDI-Guy]

I've heard that depleting the battery all the way down to zero is not all that healthy (for the battery, that is). Although good for calibration.

This. Depth Of Discharge is a huge factor in battery lifespan. The deeper the discharge, the shorter the lifespan overall.

Power management hardware prevents (usually) a complete discharge with this battery chemistry. That said, someone who runs their battery to 0% on a regular basis will not last as long as someone who recharges at 50%. There are many other factors at play, temperature, battery lot, handling, device usage / settings, altitude, humidity, charge current... So this is just one factor of many, that said, I try to limit my cycle depth when I can.

 

[reppans]

I take care of my iPad battery. Using a light timer every night, it's not much effort controlling when and how much to charge. I expect to use this iPad well past 3 yrs, if nothing else, as a hand-me-down to my kids.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Here's an interesting study done by the US army how Li-ions age with different charging habits.

http://www.cerdec.army.mil/directorates/docs/cpi/Cycled_Aged_LiIon_Cells.pdf

Bottom line, Li-ions age fastest when charged to, and maintained at, high voltages (ie, at and near full capacity).

 

[Big-TDI-Guy]

Reppans - are you aware that the first link you provided has data that completely contradicts the chart you have posted?

 

[reppans]

I don't think the two perfectly corroborate each other, but I wouldn't say they're contradictory... what part do you think is contradictory?

The problem with comparing the two is that first discusses wear factors in isolation, while the 2nd tests them in combination.

 

[reppans]

This. Depth Of Discharge is a huge factor in battery lifespan. The deeper the discharge, the shorter the lifespan overall.

Power management hardware prevents (usually) a complete discharge with this battery chemistry. That said, someone who runs their battery to 0% on a regular basis will not last as long as someone who recharges at 50%. There are many other factors at play, temperature, battery lot, handling, device usage / settings, altitude, humidity, charge current... So this is just one factor of many, that said, I try to limit my cycle depth when I can.

Ah, now that I read your post, I think I see where the confusion lies. Batt Univ does mention 1) the shallower the DoD the better and 2) reaching and maintaining high voltage the worse.

The army chart is basically saying reaching and maintaining high voltage is significantly worse than deep discharges, although deep discharges are bad too.

Cycling 100-0-100 averages at 50% voltage (or capacity) while 100-50-100 averages 75% voltage, and this higher voltage average is worse for the battery than the deeper discharge. When both average at 50% voltage (100-0-100 vs 75-25-75) the latter shallower DoD wears the battery less. When both are cycled a shallow 50% DoD (75-25-75 vs 50-0-50), the lower average voltage of 25% wears the battery less.