Laptop Battery Life

[Joseph Sinclair]

The full discharge-and-recharge was for NiCd batteries, and helped to limit memory effect, it does not apply to NiMH or LiIon batteries (anything fairly recent), nor did it ever apply to lead-acid and it's derivatives.
LiIon is the only one that has particularly big problems if discharged to 0%; although it's best to not leave any battery fully discharged too long, for various reasons depending on chemistry.

It *used* to be that chargers were quite dumb and just "shoved" charge into a battery.  Most good quality chargers are much more nuanced than that today, and will charge at different rates depending on the charge state of the battery which further extends life.
Most laptops, in particular, have quite intelligent chargers and will not overcharge the battery or charge too fast/too slow for the charge profile; this is particularly important for LiIon as overcharge and overly aggressive charge/discharge can result in thermal runaway (c.f. the various laptop "explosion" videos).

So, for LiIon, just charge it when you need to, and if you intend to store it for a while, discharge a bit (around 80%) and check it now-and-then to make sure it gets recharged before it drops much below 30%.
For NiMH, it's a bit more nuanced, but still amounts to charge-it-when-you-need-to, just not as much to worry about when storing as long as it doesn't spend too much time completely discharged.

For both LiIon and NiMH, there are several common chemistries used (both are families of battery, not particular implementations), and each has different advantages and disadvantages.
It's worthwhile checking which you're dealing with if you wish to maximize the life of your particular device.

These wikipedia articles have some very good details on the chemistry, including some of the differences for recent alternate chemistries.
http://en.wikipedia.org/wiki/Lithium-ion_battery
http://en.wikipedia.org/wiki/Nickel%E2%80%93metal_hydride_battery

I hope that helps, Rusty.


On 07/23/2012 09:13 AM, Carruth, Rusty wrote:
> Warning - what you are about to read is from the "king of rechargeable
> battery killers", so take it with a few metric tons of salt!
> 
>  
> 
> I have recently been told that, for newer-technology batteries:
> 
>  
> 
> 1 - you do not want to overcharge them - a sure killer
> 
> 2 - charging to 100% all the time risks overcharging.  Charge to 90-98%
> instead.
> 
> 3 - discharging to some point below 20% reduces battery life, avoid it.
> (I'm not sure what the lower bound is)
> 
>  
> 
> However, I have also been told:
> 
>  
> 
> A - always fully a discharge new battery and recharge fully 3 times
> before use - this is supposed to make batteries more prepared or
> something.
> 
> Vs
> 
> B - never fully discharge a battery.
> 
>  
> 
> Do we have anyone who works in the battery industry who can give us some
> real insight?
> 
>  
> 
> Rusty
> 
> From: plug-discuss-bounces at lists.plug.phoenix.az.us
> [mailto:plug-discuss-bounces at lists.plug.phoenix.az.us] On Behalf Of
> keith smith
> Sent: Monday, July 23, 2012 9:05 AM
> To: Main PLUG discussion list
> Subject: Re: Laptop Battery Life
> 
>  
> 
> 
> That would make sense.  I still do not understand why my cellular
> battery lasted over 4 years and was still viable when retired.  I had
> much less from laptop batteries. 
> 
> ------------------------
> Keith Smith
> 
> --- On Sun, 7/22/12, Michael Havens <bmike1 at gmail.com> wrote:
> 
> 
> From: Michael Havens <bmike1 at gmail.com>
> Subject: Re: Laptop Battery Life
> To: "Main PLUG discussion list" <plug-discuss at lists.plug.phoenix.az.us>
> Date: Sunday, July 22, 2012, 10:18 AM
> 
> I think it would because a rechargeable  has a maximum amount of charge
> time on it. at least that is the way it USED to be!
> 
> On Sun, Jul 22, 2012 at 9:12 AM, keith smith <klsmith2020 at yahoo.com>
> wrote:
> 
> 
> Sometime ago we discussed laptop battery life.  I asked the question
> about leaving the battery out and if that would extend the life of the
> battery.  I'm not sure that option was explored.
> 
> Last December I took the battery out of my two lap tops.  I use both
> daily for about 15 or 16 continuous hours.
> 
> I have been thinking the batteries might be fully drained by now.  Much
> to my surprise the newer laptop's battery was at 81% and the older
> laptop's battery was at 58%.
> 
> Both are taking a charge.  After they are fully charged I will put them
> back in my desk drawer and charge them again in 3 to 6 months.
> 
> I've have had poor performance from laptop batteries and did not want to
> "cook" these.  It will be interesting to see if this extends the life of
> the battery.
> 
> Any thoughts?
> 
> ------------------------
> Keith Smith
> 
> 
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