Who leaves their battery in when using AC power?

I was wondering whether I should leave my battery (9-cell Lithium Ion) in when using AC power?

Most of the time I use my T61p with AC power but the battery is always in. Should I take it out or just leave it in?

If I leave it in, will it degrade the battery?

What's the best way of getting the longest life out of my battery?

Thanks

 

Hi,

With cheaper laptops it may be worthwhile to disconnect the battery whilst on AC power, avoiding unnecessary charge of an already charged battery, but with a Thinkpad it is not necessary, because the battery is not charged anymore one it is fully charged. In actual fact you can set it up in Windows that the battery won't be charged if it is above a certain level (my T43 is set up to 96%). I hope this helps.

 

theoretically, batteries degrade also from heat. So if you could pull out the battery when not in use it's better. Now it up to you if it worth the inconvenience.

 

I have always left my 6/9 cell batteries in my T43 for the past 3 years. The argument I heard was that if the power suddenly went out I risked loss of data as well as physical damage to the hd. (Is the latter true?)

after 3 years of use, my batteries hardly hold 1+ hour of usage anymore. In fact my 6 cell now lasts longer than my 9.

For my next Thinkpad, am thinking I should leave out the battery unless I am traveling. My laptop gets continuous use during normal work hours and then at night I would sometimes move it into the living room & bedroom. forgive me if this is a silly question, but can batteries be inserted while the machine is on?

 

Yes, it can.

As for battery deterioration, I have used my 6-cell for 2 years and 9 months; going through 237 cycles during that time. It still holds 84% of its designed capacity. The only time where my battery has lost its charge was from:

1) Going below 5% battery charge left
2) Going above 95% battery charge left

 

Has anyone seen a scientific study of whether removing your battery while on mains power makes any difference to its life? As pointed out, if it is fully charged, the ThinkPad is not charging it any more, so what difference does removing it make? It also seems that a major factor is cycles, which are still going to happen whether you remove the battery or not.

I also note that ThinkPads are designed to run with the battery in! For example, if you remove the battery the maximum CPU speed drops 50%.

 

I believe you are mistaken. I ran my T61p for 3 months with no battery and I noticed no such performance loss (playing games like COD4, Mass Effect, etc).

On the other hand when you have the battery in, and then unplug AC, you will see a noticable performance loss.

 

I don't believe I am mistaken. It is certainly true for the T61 and X61, and I thought most ThinkPads. Maybe the T61p is different?

Perhaps you could check your T61p? Just fire up Resource Monitor and watch the CPU Maximum Frequency when you remove the battery while on AC power.

 

Rightmark CPU clock utility shows no difference when I remove the battery from my T61p.

 

To me, it seems like a huge advantage to be able to take the battery out.

Like probably a lot of people, I commute with my laptop and leave a charger at work. I'd like my bag to be as light as possible...

 

Woo Rightmark CPU clock is a cool little utility. I like the System Tray frequency display.

Anyhoo, it shows clearly that when I remove the battery from my X61, the maximum CPU frequency drops 50% i.e. goes from 2.4GHz max to 1.2GHz max. Seems like the X61 and the T61 do it, but not the T61p.

 

Its probably just speedstep kicking in. You should be able turn it off in BIOS and test it again with your battery out. Or just run Prime95 or something to tax your CPU

 

Or the power profile he has active.


If you set it to Maximum, the processor will always run at full speed. Balanced and Minimum allows Speedstep to kick in and it will drop your processor based on load. Removing and adding the battery also affects this.

 

Yeah I didn't believe it either when I first saw threads about this appearing.

It's nothing to do with the power profile or Speedstep. It appears to be by design. When you remove the battery, the max cpu speed is halved. I checked this out on my X61. Also, interestingly, if you disable Speedstep, the cpu speed is limited to half by the BIOS.

 

Lithium Ion batteries degrade from three things:

1. Time - Nothing you can do about it, only slow it down.
2. Heat - The hotter the environment the battery is operating in, the less life your battery will have.
3. Charge - A battery at full charge will degrade faster than one at 40-60% charge.

Typically you can expect to lose 15-20% of the battery's capacity every year.

 

I never take the battery out, because it removes one of the primary advantages of using a laptop, that is, having a battery backup in case of power failure! With the battery out, a power failure or someone accidentally kicking out my power cord will be bad...how bad is just a matter of luck. The good news is that with Lenovo's ThinkVantage Power Meter, you can maximize the lifespan of your battery by configuring the power profile intelligently. Check this Wikipedia entry on Li-Ion batteries for an awesome chart on how much capacity loss to expect per year for a typical battery: http://en.wikipedia.org/wiki/Lithium_ion#Storage_temperature_and_charge

I keep my battery charged 35% - 45% most of the time, except if I'm about to leave on a trip, at which point I'll charge it to 95% - 100%. One caveat, I'm not sure if the Power Meter settings are used while the laptop is hibernating or powered off (but plugged in). Does anyone know? I almost never turn my laptop off, but I've never noticed it at 100% charge unexpectedly, so I assume it works even when the OS isn't running. This one "minor" convenience really makes me happy with my Thinkpad, vs. all the other laptop brands where battery management like this is not possible and you're ususally left with an overcharged battery that hardly holds an hour charge after a year or two.

 

on my T42P few back i started taking my battery out but unfortunately lots of times the power cable gets removed for sudden move and i feel sorry

let that battery burns to hell rather than losing data

battery now is only 18% of its power so its time to replace it (i dont use the laptop without charger these days heh)

 

@Fignuts:

this figures are amazing!! so how come Lenovo sets the power manager to automatically charge to 96% when you define in power manager that you want to work mainly on AC and not battery?

 

Agreed.

I really don’t understand this behavior. I’d rather have my almost completely full battery ready to go at all times—and spend 50 bucks every two or so years (and this assumes I keep the notebook that long)—than only have one-third battery life at any point in time.

 

I always leave my battery in.

1 - like others have mentioned if the power goes out my laptop is fine.

2 - I'm too lazy to take take the battery out and store it somewhere.

3 - All batteries will eventually lose capacity no matter what you do. After a few years it's probably time to get a new battery. By that time it might also be time to get a new notebook.

 

Batteries, whether in a flashlight or a notebook, are consumables. I value my data over my battery, so the battery is in place at all times.

 

So, you are saying that my allwaaaays plugged battery and power cord makes my battery to lose charge??? because I use it almost everyday charged!

 

gosh why dont they develop better batteries already...it seems like taking care of a lithium ion battery is like taking care of a friggen child...

 

Are you sure about this, I mean have you tried inserting and taking out the battery with the laptop on and plugged in to AC power? Or is there any documentation that says this is OK?

For me the chance of accidental loss of power during work hours are very low so I am willing to take the chance and leave the battery out. If I could simply insert a battery while Windows is still running that would be great. I've never tried it but I've always shut down (or hibernate) the laptop before changing batteries.

 

I just took out my T61p 9-cell and reinserted it with Windows XP running earlier today. No incident.

 

I think it's a usability choice. For people who are always using their laptop on the go, I agree it would be an inconvenience and a waste of the battery's intended function. I work from home full time, rarely travel far from an AC plug, and my laptop is plugged into AC power at almost all times, so I really never need the battery except for a cross-country flight or something (or when switching locations in my house). I've never once been inconvenienced by keeping my battery at 40% charge, so if doing so extends the life of the battery significantly, then great! Honestly, I'm more just curious to see how long I can make this battery last (I know from personal experience how quickly batteries die when kept fully charged all the time). I agree that li-ion batteries (as they are currently designed) should be treated as limited-lifespan devices. I'm very much looking forward to laptop fuel cells and perhaps MIT's ultracapacitors...

 

Thanks for the confirmation.

I work from home like you, and didn't know that keeping them charged at 100% degrades the life of a LiIon battery faster. After subjecting my batteries to 3 years of 100% full charging, I doubt anything I do now can help, but I'll start getting into the practice of not keeping the battery charged fully all the time.

Out of curiosity, what should my settings be? Should start charging when below and stop charging both be the same %?

 

I've seen recommendations of start charging when below 36% and stop charging at 40%.

 

You make it sound like it is so easy....

We really need a mechanical way of storing energy instead of the chemical battery.