battery life question

[Arthur7258]

I've just read that a lithium-ion battery last longer when held at a lesser charge (around 40%). I can't find that option on my older model Mac Book Pro. Is there an app to help me hold this level. I've been leaving it plugged in and around the 90% level most of the time. This is important to me as I bought the older model Mac Book Pro with a dead battery that was easily replaceable, but, my partner bought a new model Mac Book Pro that has to go back to Apple to have the battery replaced. The issue is also going to happen with the new droid cell phone I just purchased. How do I keep it low enough to be healthy for the battery without becoming a freak that checks the battery levels every few minutes! Right now my Mac Book Pro is in sleep mode with still 91% charge - I don't use it that often. I need something to help me keep track of this!

Thanks,
Arthur

 

[pigoo3]

I've just read that a lithium-ion battery last longer when held at a lesser charge (around 40%).

How about a link for the source of this info...I would love to read about it.

- Nick

 

[Larry H]

I found this at Wikipedia

Cell life

* Charging forms deposits inside the electrolyte that inhibit ion transport. Over time, the cell's capacity diminishes. The increase in internal resistance reduces the cell's ability to deliver current. This problem is more pronounced in high-current applications. The decrease means that older batteries do not charge as much as new ones (charging time required decreases proportionally).
* High charge levels and elevated temperatures (whether from charging or ambient air) hasten capacity loss.[37][38] Charging heat is caused by the carbon anode (typically replaced with lithium titanate which drastically reduces damage from charging, including expansion and other factors).[39]
* A Standard (Cobalt) Li-Ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.[40][citation needed] In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.[41]

Link to full article: http://en.wikipedia.org/wiki/Lithium-ion_battery

Larry H

 

[pigoo3]

I found this at Wikipedia

Link to full article:

Thanks for the info. I wanted to read more...but the link just circles back to this thread...not the full article.

- Nick

 

[Larry H]

Here is another site with similar info:

How to prolong lithium-based batteries

Larry H

On Edit: I fixed the link in post #3, correct URL http://en.wikipedia.org/wiki/Lithium-ion_battery

 

[pigoo3]

Here is another site with similar info:

How to prolong lithium-based batteries

Larry H

Thanks again for the link. This article explained it well (the chart). Yes it says that storing a Lith-ion battery at 25°C and 40% charge maximizes long-term battery capacity. But as the OP mentioned...it's pretty darn difficult to keep a stored battery at 40%...since even a stored battery will lose charge over time.

For example...I've heard (don't have a link) that a stored battery will be ok for about 6 months before needing to be recharged. That's 24 weeks divided into 100% = about 3-4% charge loss/week. So a battery stored at 40% charge, after just one week will be at 38-39%...and after 1 month of storage will go from 40% to 24-28%.

Even if this info is not 100% correct...the fact is a stored battery loses charge over time. So maintaining a stored battery at exactly 40% is very difficult. Thus in theory it sounds great...but in real-life...tough to manage.

Thanks again for the links,

- Nick

 

[chas_m]

You guys are aware that everything you're discussing is *strictly* regarding long-term STORAGE (ie separated from computer, not in use) of a Li-On battery and has *no* bearing on batteries that are in practical everyday use, right?

 

[pigoo3]

You guys are aware that everything you're discussing is *strictly* regarding long-term STORAGE (ie separated from computer, not in use) of a Li-On battery and has *no* bearing on batteries that are in practical everyday use, right?

That's exactly the point of view I was discussing from.

- Nick

 

[Larry H]

chas_m,

While this info doesn't help with computer batteries in regular service, it does indicate that other lithium ion batteries (like my Makita tool batteries)should be 'stored' between uses at lower rather than higher temps.

Larry H

 

[MacInWin]

"Stored" is different than "not used" when the battery is in the laptop/phone/device. When used, even lightly, Li batteries like to be kept full, above 90%, as much as possible. They lose life when deeply discharged. The idea behind storing at 40% is a compromise. You need some charge to even recharge it, but you don't want to have it sit all topped off and nowhere to go as that lets the calibration of the internal charge monitor get messed up. So, in the MBP in service like the OP described, keep it topped up and you'll maximize the battery usefulness.