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Posts: 11
Registered: ‎01-31-2013
Location: Ohio
Views: 16,696
Message 1 of 2

Battery design capacity and full charge capacity are lower

I have an X230 with 6 cell battery. The OS is Windows 8. I've noted that the design capacity and full charge capacity are both lower with 9 cycle counts. The design capacity is 57720mWh and the full charge capacity is 57420mWh while these two figures should be 62160mWh for the new battery. I know that the full charge capacity will be reduced after use while I have two questions:


1. Considering there are only 9 charging cycle, now the figure are too low for the full cycle charge. It means 7.6% loss after 9 cycle charge. It is so ridiculous.


2. Why the design capacity is reduced? Is it should not be changed, right?


I noticed a knowledge base lead abt the design capacity.


While my OS is Windows 8, there is no Power Manager, so I can not understand the explanation exactly and do not know how to recovery the battery.


Pls kindly check my questions and help me to figure it out, thanks!

Posts: 146
Registered: ‎02-06-2009
Location: Portland, OR
Views: 16,278
Message 2 of 2

PowerManager battery charge threshold function in Windows 8 through registry edit.

I could think of one reason why it might be like that. Lenovo might have artificially limited the max full capacity of the battery in the batterypack firmware (it was suprising to me that battery also has its own firmware!) so that there is never a overcharge on one of the cells inside the battery pack. I've seen this in a Toshiba Portege R835 laptop too.


It's nearly impossible to have exact same capacity for each cells (called cell balancing), so when you try to charge a batterypack with 95% charge all the way up to 100%, one cell might already have reached its 100% (this is the inferior cell) while one cell is only at 90% (this is the superior cell). The batterypack will try to keep charging all the cells resulting in overcharge for the inferior cell and degrade it even more quickly.


By limiting the maximum capacity to less than 100%, it helps prolong the battery life, and similar effect can also be achieved using using the PowerManager tool in Windows 7 by restricting the charge threshold (configure the setting so it stops charging at 90% for example). I don't know why they don't create a Windows 8 version though. So in Windows 8 what I do is add a registry key which limits the max charge capacity. This needs to be done only once, but if you ever see it behaving differently, then you could re-add the registry key and it should work again.



Below is a .reg file that I use to set the battery charge only starts at 70% and stop at 90%.


Windows Registry Editor Version 5.00




I bumped into your thread while I was searching if I could manually set the max capacity of the batterypack through altering the firmware, but that may be a hard work with no knowledge about how the firmware works. I have a X230T with a Sanyo 6cell by the way.


I have 51 cycles on my 6cell battery with design capacity of 62.16Wh, full charge capacity 62.10Wh. It's working well so far after one year.

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