Thinkpads Forum

Im sure everyone but me knows this, but what are the advantages of telling a battery to stop charging at say... 95% as opposed to charging it up the whole way, does this increase the cycles you get or something?

I read that several people would like this option on their thinkpad, and I was just curious as to why...

Thanks

rcrooks wrote:Im sure everyone but me knows this, but what are the advantages of telling a battery to stop charging at say... 95% as opposed to charging it up the whole way, does this increase the cycles you get or something?

I read that several people would like this option on their thinkpad, and I was just curious as to why...

Thanks

I think that you are looking at it the wrong way -as I understand it. The battery starts charging when the charge drops to 95% or below (or whatever your limit is set to.) It then only charges it up a relatively small amount, to 100%, which must keep the temp down, hence saves life of battery.

I did think of reducing my charge setting to 50%, but then that would mean a long recharge with a big temp rise, hence reduced battery life.

As I run on mains power almost all the time, the short recharges are required once a week or so to top the battery up.

Hope this helps.

Nick

Actually, there is a setting for both of them: One to tell TP to stop charging when it reaches a certain value, and one to tell TP to start charging again when it drops down under a certain value. Also the diffecence between these two values must be higher than 4% (To avoid fluctuating in a short period of time)

The reason of setting such values is due to the fact that the battery capacity decreases much faster when it is stored fully charged. If the laptop is used mostly on AC power, the battery will be at 100% most of the time as well. At the end of my long experiments (took about three months) I decided to set those values to 90% and 94%. This way the capacity decreases only .004 Wh per day, comparing to .14 Wh per day when it was at 100% all the time. Personally, to have a longer battery life, I don't mind starting with 94% charge instead of 100% when I need battery power.

this sounds great, I went into the power management and told it to use the 90 and 94 settings, I am on AC alot, so this will hopefully increase my battery life, thanks for the tip sir.

On my old dell inspiron I had for 3 years, I had 2 batteries in that time, left the computer on AC like 24/7 almost, and found that both batteries would only give me around 20 minutes, now I know why

Can you note down the date and the capacity, and check back in two weeks?
I would be interested to see how is it going to work out for you.

sure will, I assume you mean total wear %, capacity, and full capacity??

Ill go ahead and post start stats now:


Thinkpad is 3 days old, battery was new at that point:

Full Capacity= 49250mWh
Capacity= 45760 mWh
Wear% = 4

Settings: 90 -> 94% start/stop charge

If it matters, I also have it undervolted, and running 800 Mhz @ .714 volts while on battery

You only need to check the full capacity at a later time again (like in two weeks), and divide the decrease in the full capacity by the number of the days. This will give you the rate of deterioration [Wh per day].

Also you can see how much Wh did you loose so far by comparing your current "Full Capacity" to "Design Capacity".

Well sorry if bumping this annoys people but Im bored and curious, so I just checked battery settings.

Yesterday I used the battery for about 1 hour.

After 1 day:

Full Capacity= 49210 mWh
Capacity= 45790 mWh
Wear%= 5
For a loss of....

.04 Wh

Day 2

Didnt use the battery, max capacity still at 49210mWh

Wear still at 5%

Loss of 0

hiyel wrote:Actually, there is a setting for both of them: ....This way the capacity decreases only .004 Wh per day, comparing to .14 Wh per day when it was at 100% all the time. Personally, to have a longer battery life, I don't mind starting with 94% charge instead of 100% when I need battery power.

Very interesting -and apologies to rcrooks; I had not found the two settings, only the one. Odd implementation in that the help info says "The settings are effective only when the Power Manager Gauge is running in the task bar."
Nick

Nick Y:
I'm using the latest version of power manager software (1.12). Go to "Battery Information" tab and then click "Battery Maintenance", there should be the "Custom" option under "Charge Treshholds", that allows you to set "start charging" and "stop charging" percentages.

Also, I didn't see the help info you mentioned but, I don't run the power manager gauge, and the treshholds work properly. This ugly gauge is just a gauge, what controls the tresholds is ibmpmsvc.exe running in the background.

hiyel wrote:Also, I didn't see the help info you mentioned but, I don't run the power manager gauge, and the treshholds work properly. This ugly gauge is just a gauge, what controls the tresholds is ibmpmsvc.exe running in the background.

Thanks and I am on 1.12 as well. I found the thresholds. If you then select the help box you get Tips for Maximising Battery Lifespan. Item 4 has, at the end of the paragraph, a link to 'Learn about changing the battery charge thresholds. ' The gauge info is at the end, in green.
As you said, I expected the power sensing to be done continuously by s/w, although I had not looked into the control, and hence I was surprised to find the stated need for the gauge to be running -taking up bar space. Help info not updated?

Nick

Yea, I saw it, it doesn't make sense to me, who knows!

Another example of battery life extension would be my settings.
Since I use the R51 everyday on batteries I have learned that I almost never need more than 50% of a charge. And given that I have set alarms and actions to protect my data at 10% and 3% I don't consider the bottom 10% as for anything but emergency use.
So... my charge start % is set to 40% and my charge stop is set to 70%.
When I know that I will be having an extra long day away from the line charger, I will set it to fill the battery. But this is less often than one day a month and as I have it set, each regular day has a 10% cusion built in.
I never turn the R51 off. I use standby mode, sometimes for up to 16 hours at a stretch.

update: Full capacity: 49170 mWh
Wear still at 5%

interesting thread. Got me to get the latest Power Manager (1.12) and install it on my X32.

Unfortunately, I still don't see the threshold settings options mentioned above by hiyel.

I double checked that the Power Manager had been upgraded to 1.12, and the About info confirms it. Any ideas? Thanks!

Well I got a 9 cell and a slimbay now, so I dont really care if my 6 cell wears out... I turned the charge back up to 100%

that said, I checked it just now

48500~ mWh, so it went down almost 50 mWh's per day over the past 10 days I havent been checking it

anyone know if its possible to set acpi to stop charging the battery at around 94-95 percent on Linux??

i havent found a specific option or script...wondering if anyone has already got a bash script going?

Hit www.thinkwiki.org. All kinds o' answers there.

hiyel wrote:Nick Y:
I'm using the latest version of power manager software (1.12). Go to "Battery Information" tab and then click "Battery Maintenance", there should be the "Custom" option under "Charge Treshholds", that allows you to set "start charging" and "stop charging" percentages.

Also, I didn't see the help info you mentioned but, I don't run the power manager gauge, and the treshholds work properly. This ugly gauge is just a gauge, what controls the tresholds is ibmpmsvc.exe running in the background.

Do these options still exist in newer versions of power manager? I am assuming that the program is the one that I access from either the control panel or access IBM folder. I just can't find the customise tab.

pksw wrote:Do these options still exist in newer versions of power manager?

Not for the earlier T4x models, like your T41, which have a fixed charge threshold point. The T43s have a variable point, but in practice there no noticeable difference in battery performance, in my experience.

Cheers,

Bill

are you sure setting at 90 and 94% is the best?
i was under the impression that you'd have a longer battery life if nearly fully discharging before charging, and when you do charge to let it fully go back up to 100%. so you don't get memory. otherwise when your battery gets lower than what it's used to, it won't really last very long.
am i just completely wrong?

Allen:
90% and 94% are for when it is on A/C power, to tell TP when to start and stop charging. If you are on batteries you will be discharging it anyways as long as you use it. If what you meant was using the batteries to drain them fully, even when you have access to A/C, I think that will kill the battery even faster because you would be constanly using the battery and increasing the cycle count. In the A/C case however, you are just "storing" the battery and not using it at all. What we were just discussing was that what is the percentage of charge is best for storing it. Plus, if you use your laptop the way you described all the time, what will happend if you need to take it away from A/C while the batteries are almost empty. You will have to wait until they are fully charged, which misses the point of having a battery powered mobile device.

allen wrote:are you sure setting at 90 and 94% is the best?
i was under the impression that you'd have a longer battery life if nearly fully discharging before charging, and when you do charge to let it fully go back up to 100%. so you don't get memory. otherwise when your battery gets lower than what it's used to, it won't really last very long.
am i just completely wrong?

Those kind of charging and power management policies were designed primarily for NiMH batteries, which had memories and were best used when cycled periodically to reset/negate the memory effect. LiIon batteries, which are used on almost all modern laptops including Thinkpads, don't have that issue (they still develop a memory, but over a very long period of time such that it is negligible) so you don't have to worry about fully deep cycling LiIon batteries. In fact, deep cycles should only be done to recalibrate LiIon batteries as a true deep cycle to 0% indicated charge can reduce the capacity of the battery as well as increase the wear level.

wow, i'm glad to have found this post,
so hiyel, are you saying the 90 and 94% are the best settings you found after 3 months of testing? better than having a larger than 4% difference, or better than having it stored at 98 or 99%?

Hi Allen,
I posted some numbers here: http://forum.thinkpads.com/viewtopic.ph ... 956#235956
Power manager does not allow you to have a lower difference than 4% between the two numbers. So I kept it at 4%, this was more like a preference. I didn't want to wait too much before it starts to charge so in case I need the laptop off the A/C, I don't end up lower than 90% charge. What I was trying to find was a storing charge level (94% in this case). This number had to be a high number so that I always have a high amount of energy. But it also had to be low so that the wearing rate is slow (we already know that storing it in low charge reduces the wearing rate). So I started with 80%-84% and walked my way up from there. I was checking the wear every two weeks. At the end I decided to keep it at 90%-94% which gave me a wear rate of roughly .18Wh per month. For me, this means at least 2 hours of normal use charge, even after two years from now.

Also, one other thing that I noticed was that, sometimes the power manager sets back its default values. I'm not sure why but it usually happens when explorer.exe crahes (when you loose the whole taskbar). So I go to the task manager and rerun explorer.exe. After that, I get that ugly green battery indicator back on the taskbar (I always keep it hidden). So I know that the power manager's settings are back to default. I go and set the percentages back to 90 and 94.

thanks for the explanation, i really appreciate it, being kind of a control freak and obssessive, and wanting my expensive equipment to last as long as possible, and feeling like i need to know why i'm doing something, it's a big help
thanks!

Hey guys, what about storing your battery? would that work better or would it be worse off for the battery?
In my case I honestly only use the battery maybe once every 4 months or so (when i take my laptop on a trip). Other than that I use my laptop with the a/c. I kept my battery on the laptop since i got it in march and it's now in "poor" condition (although i did not use the power manager settings). I called Lenovo and I'm getting a replacement, just wanna make sure i this one lasts more than 8 months on me....
Given that I use the battery so seldom, am I still better off keeping it in the laptop and setting a 90-94 threshold? or maybe just charging it to a certain % and storing it, and maybe re-plugging it once a month or so to recharge?
Thanks!

Louis wrote:Hey guys, what about storing your battery? would that work better or would it be worse off for the battery?

My understanding is that Li ion batteries last longest when they are stored at about 50% charge. (They also do better if they are not fully charged and not fully discharged; as in the way battery packs in Toyota hybrids are run). Batteries loose capacity if they get warm, and there is some benefit to keeping batteries cool.

So, if you use your battery very infrequently, I would let it run down to ~50% +/- 10% and leave it at that point. You could keep it attached to your computer and set the Power Manager to start charging at 40% and stop at 60% so it would stay within that range while you are not traveling. Before a trip, set the start-charge threshold below the battery's current level (e.g. 30%) so it begins charging, and set the stop-charge point to 90-100%, depending on your capacity needs.

Some compulsive folk keep the battery in the refrigerator when it's not being used. This probably adds some lifespan at the cost of worrying about avoiding condensation; storage in a sealed plastic bag with desiccant is a good idea. I don't find this worth it and just leave the battery attached to my computer.

sorry if I missed this in the thread, but where do I see 'wear %' ? On the 'battery maintenance' tab, I see things like cycle count, remaining capacity, etc, but nothing about 'wear'.

Very interesting thread!