battery discharging even when plugged in

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amb00 · #1 Post by **amb00** » Wed Apr 27, 2011 7:31 am

I have a t400 and my battery (9cell) is discharging even when the laptop is plugged in.
BIOS is verified, so when shutdown it won't consume useless power (lan, usb, etc).
Even if the laptop is plugged, when _shutdown_, it still consumes power from battery. Apparently it also happens if it is _on_.

Power manager is on "always fully charge". It was also set on "optimise battery".
But I really don't trust Lenovo with the batteries. It seems they kinda forgot they only have Li Ion and not also NiMh because some tips are specifically for nimh and _will ruin_ liion.

The power consumption is not much but is decreasing by 1% every 1.5 days.

Is this normal ?

hunterman223 · #2 Post by **hunterman223** » Thu Apr 28, 2011 4:08 pm

Which wattage of power supply do you have? Is it genuine lenovo?

Do you mean the capacity is degrading by 1% every 1.5 days?

craigmontHunter · #3 Post by **craigmontHunter** » Thu Apr 28, 2011 7:57 pm

Yes it is normal to loose some power over time. The battery uses the charge to keep the internal circitry going. The reason this appears in the thinkpad and not other systems is because thinkpads (by default) only start charging when the precentage drops below 96%, to reduce the number of cycles on the battery. That is adjustible in power manager, but in answer to your question, that is normal behaviour.

Colonel O'Neill · #4 Post by **Colonel O'Neill** » Thu Apr 28, 2011 8:22 pm

Doesn't it also use a bit from battery for peak power draws?

craigmontHunter · #5 Post by **craigmontHunter** » Thu Apr 28, 2011 9:10 pm

It may - especially if you are using a smaller power supply (which would answer the question about why it throttles if running without a battery) - I have never seen that with my t61 (with intergraded graphics), but I have seen ~6hr charge times when using the 65 watt adapter and a heavy load.

I think the issue here is just the battery uses juice, and it does not top up. In regards to the instructions, while it is true that deep-cycling a li-ion battery is bad for it, if you don't do it occasionally the gauge will become inaccurate. In this case, it is not the memory effect of the battery that you are correcting, but the memory effect of the electronics, which cannot calculate the wear (or lack thereof) if it cannot see how much power the battery actually holds.

amb00 · #6 Post by **amb00** » Sat Apr 30, 2011 6:27 am

hunterman223 wrote:Which wattage of power supply do you have? Is it genuine lenovo?

Do you mean the capacity is degrading by 1% every 1.5 days?

Wattage is 65 and yes, it is genuine.

Yes, I loose 1% of the battery every 1.5 days even though it does nothing. Of course it can be charged back to 100 but these are useless cycles.

amb00 · #7 Post by **amb00** » Sat Apr 30, 2011 6:31 am

craigmontHunter wrote:Yes it is normal to loose some power over time. The battery uses the charge to keep the internal circitry going. The reason this appears in the thinkpad and not other systems is because thinkpads (by default) only start charging when the precentage drops below 96%, to reduce the number of cycles on the battery. That is adjustible in power manager, but in answer to your question, that is normal behaviour.

I know this. Li Ion batteries discharge over time but not this fast !.
The "is this normal?" question was more like a rhetorical question because it is not normal in such a short time.

Edit: For now it stopped (I think)... The percent is still 100 and I haven't done anything special. Just reinstalled some drivers, messed with the bios again and reconfigured the power manager settings.
I mean 28 hours passed and no discharge. I hope for the best

Colonel O'Neill · #8 Post by **Colonel O'Neill** » Sat Apr 30, 2011 3:21 pm

A cycle is every full charge equivalent, not every time it hits 100%. You generally don't want to charge it to 100% anyway. IIRC, discharge rate is proportional to stored charge, so a full battery might discharge a lot more at 100% than at say 40%.

Tableteer · #9 Post by **Tableteer** » Wed Jun 15, 2011 9:31 pm

It happens too on my W701 too although at a slower rate than on your T400....0.24 or 0.25 WHr per day, approximately 1%/3 days.

At the 95% capacity, the battery is recharged back up to 100% as usual for the Lenovo power manager. BUT here's the difference: the total (or full charge capacity) lowers slightly each time. This cycle keeps repeating. So now the battery's total capacity is only 72-something Whr, down from the design capacity of 84 Whr! That's down to 86%. And there are ONLY 10 battery cycles!

Battery self discharging even when plugged into AC also occurs on my X201 tablet BUT the full charge capacity doesn't decrement. In fact, with 16 cycles, it's still ABOVE the design capacity.

I think there's something wrong with select Lenovo batteries and/or power manager software in some models.

craigmontHunter · #10 Post by **craigmontHunter** » Wed Jun 15, 2011 9:44 pm

@tableteer - the age of the battery also affects the charge capacity, regardless of the use, with an *average* capacity loss of 30% a year (at the end of the standard 1 year warrenty, a normal battery can hold 70% of it's design capacity) - on my T61, the battery is at 90% of design with 182 cycles and first being used in september 2010. For the first while (80 cycles or so), it was above the design capacity, decreasing fairly consistantly, I expect I will be at or just over 70% of the capacity when the one year point comes around.

Tableteer · #11 Post by **Tableteer** » Wed Jun 15, 2011 10:09 pm

Understood about the battery capacity decreasing with age. What I find curious is the 72 Whr capacity (a decrease to 86%) was at the 9 month mark with less than a dozen charge cycles (about 1 cycle per month). It's been more or less my desktop replacement computer so the battery has not been stressed.