LaTop battery care and life expectancy

Tue Oct 11 14:01:47 MST 2011

Thank you Joseph for take the time to explain all this to me.  I think I understand better.  Since my laptop runs without a batter if plugged in I assume I should only place the batter in my laptop when I plan to run it on batter power only.

The battery has been out for several months and it is still at 80% .  Will it hurt the battery to let it self discharge for a few months?

Thank again for this wealth of info and thank you to everyone who responded.

------------------------

Keith Smith

--- On Sun, 10/9/11, Joseph Sinclair <plug-discussion at stcaz.net> wrote:

From: Joseph Sinclair <plug-discussion at stcaz.net>
Subject: Re: LaTop battery care and life expectancy
To: "Main PLUG discussion list" <plug-discuss at lists.plug.phoenix.az.us>
Date: Sunday, October 9, 2011, 2:47 PM

All Lithium-Ion batteries have similar issues and, in general, similar recommendations for care.
Keep in mind, however, that different chemistries produce very different results, lead acid is very different from NiCd, NIMH, or LiIon.  Different batteries using the same general chemistry may still have very different specific chemistry to meet particular cost/current/charge/voltage characteristics. Lithium ion, for example, has at least 8 primary chemistries (e.g. LiPo, LiFe, LiZnCo, etc...), each with a hundred or more variations.
Solar systems often use deep-cycle lead-acid because it is cheap, mature, and very rugged.  That makes comparing solar experience to laptops somewhat difficult.

Some newer Lithium Ion batteries use new chemistry (e.g. Si cathodes in charge-carrier flexible polymer matrix to accommodate swelling during charge/discharge) to adapt to the issues below, but all still face the same challenges to a greater or lesser extent.

1) Lithium Ion involves actual absorption and release of Lithium atoms by anode and cathode.

This means that there is physical stress on the battery elements, and over time this will damage the materials.  Deep discharge cycles and higher current drain will make these happen faster.
Your cellphone battery has low current drain and long cycles, compared to a laptop, and will tend to last longer as a result.
Letting your battery fully discharge before charging it will cause damage, but LiIon also has an explosive chemistry, so power management circuitry manages the battery, and turns off a phone when there is still about 20% charge left in the cell to mitigate this for cellphone batteries.
The ideal usage is to charge at about 30% and not leave the cell above 70% for too long (see issue 2 for the reason).

2) Lithium Ion current limits are dependent on the Li mobility, which requires highly solvent electrolytes to permit high current usage.

This means that the anode and cathode materials will dissolve in the electrolyte over time, and, because of the electrical potential between anode and cathode, will form whisker structures that eventually short across the gap between the electrodes.
Leaving the cell fully charged for a long time (or constantly charging it when not in use) will encourage these whisker structures to grow because it maintains a higher potential between the electrodes.  This is why leaving a battery in a charger for a long time (months or years depending on the battery and charger) will eventually result in a dead battery, even though it was never really used.
Modern charging circuitry could account for this by discharging the battery periodically, but laptops and other consumer-oriented devices generally do not in order to maintain immediate readiness for on-battery use while charging.
The recommendation is to actually use the device powered by the battery from most of the time, and only add A/C power to recharge, when planning to disconnect in the near future, or when usage duration is reasonably expected to exceed battery life (even then starting on battery and adding A/C when charge drops below 50% often helps).  It's also best not to leave a laptop always connected to power, and only plug in when charging is actually needed.

In the end, the reason a cellphone battery often lasts so much longer than a laptop battery (typically 2-3 times as many charge/discharge cycles) is more about the different power requirements of the two uses and the specific structure and chemistry choices made to match battery to load.
Research is constantly advancing battery and other electrical energy storage technologies, so the performance one may expect for a given usage are constantly changing, and different manufacturers may use very different approaches to meet specific cost and performance criteria.  This makes comparing, or even predicting, battery life very difficult, to the point of being little more than a guess, so the best advice I know is to simply use the device in a reasonable manner, and keep an eye on the lifespan indicator via the battery information probe available in Linux so you have some advance warning when you'll need to purchase a new battery.

==Joseph++

On 10/09/2011 01:22 PM, keith smith wrote:
> 
> 
> I've had several laptops and battery longevity has always been an issue.� Not how long it will run my laptop before completely discharging, but how long it will be before that battery is no good.� What I do not understand is why or how a battery can go bad from being in a laptop that is plugged in and why there is a overcharging issue. � 
> 
> I have two frames of reference, maybe three.� My cordless phone battery lasts for years.� I recently started researching solar power.� Seems some think the battery's life is extended by not draining it and having a constant change trickling into it.� One of the videos said the life of the battery was in cycles.
> 
> My cellular phone is 3 and a half years old.� My wife tends to forget to charge her phone periodically and the battery discharges to the point the phone shuts down.� We switch batteries because I keep mine charged for the most part and rarely leave home because I work out of my house.
> 
> The battery in my last laptop, about 8 years ago, went out in about 3 years.� 
> 
> I have removed the battery from my current laptop hoping to extend it's life expectancy.� I rarely using my laptop away from my home office.� When I do I try not to go on battery power, however the battery is being charged at that point.
> 
> My experience makes me wonder why my cellular battery can last 3 plus years and might last 5 or 6 years, maybe longer. � And my laptop battery is only good for 2 or 3 years.
> 
> I've read a lot about laptop battery care, however it is still not clear how to keep from wasting a perfectly good battery in just a few years .� I'd really like to be able to buy a laptop and be able to use it for 5 years.� What is the best way to approach laptop batteries?
> 
> Thank you for your help.
> 
> ------------------------
> 
> Keith Smith
> 
> 
> 
> ---------------------------------------------------
> PLUG-discuss mailing list - PLUG-discuss at lists.plug.phoenix.az.us
> To subscribe, unsubscribe, or to change your mail settings:
> http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss

-----Inline Attachment Follows-----

---------------------------------------------------
PLUG-discuss mailing list - PLUG-discuss at lists.plug.phoenix.az.us
To subscribe, unsubscribe, or to change your mail settings:
http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.PLUG.phoenix.az.us/pipermail/plug-discuss/attachments/20111011/cc8e2d14/attachment.html>