Battery on T400 won't charge past 99%

I have a new T400 and previously it charged up to 100% and maintained that while plugged in but now I started it on battery power for a minute or two and it won't charge back to 100%.

What's going on here? Should I be worried?

 

I think the battery won't charge unless you start it from less than 95%

 

Default charge thresholds are start at 95% stop at 100%. All rechargeable batteries will lose a little bit of charge just as a consequence of existing. It could easily drop from 100% to 99% despite being plugged in.

You don't want it to be charging all the time anyway. It is bad for Li-ion batteries to be kept at full charge for long periods. It is also bad to just trickle in a top off charge all the time.

If you mainly use your computer at your desk you may even want to LOWER YOUR THRESHOLDS so it charges even less. I use 60% start and 95% stop on my x200 Tablet. I get enough battery life at 60% to get me through most days, and this method prevents my battery from being cycled too frequently (helps with battery capacity a year down the line).

 

Thanks, I'll do that. I've had the computer for less than two days old. Should it really drop to 99% after a day?

The default charge max is set to 100%.

 

This is great advice. Thanks!

My wife is of the mind-set that she ALWAYS plugs-in the laptop whenever she uses it regardless of how much battery is left. She will not change her ways.

If I lower the thresholds as you mention above will this prevent cycling too frequently and left the life-span of the battery?

Where do you specify the thresholds?

If I set the thresholds to what you mention above and my wife insisted, could the laptop be plugged in night & day without any harm (other than the green effect)?

 

Launch power manager and go to the advanced tab. You should see an option for battery maintenance. You can then specify custom thresholds.

These thresholds will prevent frequent cycling of the battery. This should improve long term life (more of the design WHr remains after a year).

The laptop can be plugged in all the time, with the battery inserted, if you set the thresholds this way. The battery will show activity as 'Idle' even when plugged in and running if it is above the thresholds (e.g. if I plug it in and use it with a 73% battery, it just stays there).

60-95% are just the thresholds I am most comfortable with. If you have it on the desk all the time you may want something even lower (e.g. 30-50%). If you need a lot of battery life on a day to day basis, you may be better served by something higher (e.g. 80-100%). Just experiment and find the setting that works best for you.

I believe Lenovo uses 95-100% as default primarily to minimize the number of support calls from people like the OP asking why their battery refuses to charge.

 

NM. Sloppy reading on my part.

 

You should stop charging at 95%. Lithium batteries do not like staying at 0% or 100% charge.

 

There should also be a battery refresh utility that will refresh it so it charges back up to %100. Frankly though since it's a new computer I wouldn't worry too much about it. I ran the refresh utility after about 6months when my R61 started stopping at %98 and all is good again. I think the other posters are correct though and your system is set to not recharge until it drops below 95%, that's how mine came, but like mentioned I lowered my recharge threshold to %75 to keep the number of recharges to a minimum.