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Token Ring
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Posts: 486
Registered: ‎11-04-2010
Location: Sydney
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27++ battery discharge pattern

So, I have two batteries.  55++ and the 27++.  Both are 9cells each, and with a designed capacity of 93.24Wh.

 

The dischrge pattern between the batteries while they're both hocked up to the W520 is that the 27++ will first get dischange...all the way down to 0%, then and only then will the 55++ start to discharge.

 

This is potentially damaning to the 27++ in terms of faster wear, and long term battery health.

 

Is there a way to configure the system to switch over and use the 55++ battery once the 27++ drops down to a particular level, say, 25%.  ...without manually disconnecting the 27++?

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harrisb
Posts: 1,017
Registered: ‎04-20-2008
Location: Cary, NC
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Re: 27++ battery discharge pattern

[ Edited ]

The slice battery is protected from total discharge.The system will switch over to the internal battery when the microprocessor on the slice battery signals that it is at 0%. The microprocessor will protect the battery from further discharge when that power state is reached.

W520, i7-2820QM, BIOS 1.41, 1920x1080 FHD, 32 GB RAM, 2000M NVIDIA GPU, Samsung 840 Pro 480GB SSD, Hitachi 1TB 7200rpm HDD, WD 2TB USB 3.0, eSata Plextor PX-LB950UE BluRay

W520, i7-2760QM, BIOS 1.41 1920x1080 FHD, 32 GB RAM, 1000M NVIDIA GPU, Crucial M500 480GB mSata SSD, Hitachi 500GB HDD, WD 2TB USB 3.0
Token Ring
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Posts: 486
Registered: ‎11-04-2010
Location: Sydney
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Re: 27++ battery discharge pattern

So even when the slice is reporting 0%, it in fact is not the cells' 0%?  Am I understanding correctly?

 

Does this logic also apply to the 55++?

 

 

Guru
harrisb
Posts: 1,017
Registered: ‎04-20-2008
Location: Cary, NC
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Re: 27++ battery discharge pattern

[ Edited ]

Yes, the 0% is not the cell discharge level, but the 0% of power that can be safely drawn from the battery. All Li-on batteries from Lenovo have the builtin microprocessor that protects the cells.

W520, i7-2820QM, BIOS 1.41, 1920x1080 FHD, 32 GB RAM, 2000M NVIDIA GPU, Samsung 840 Pro 480GB SSD, Hitachi 1TB 7200rpm HDD, WD 2TB USB 3.0, eSata Plextor PX-LB950UE BluRay

W520, i7-2760QM, BIOS 1.41 1920x1080 FHD, 32 GB RAM, 1000M NVIDIA GPU, Crucial M500 480GB mSata SSD, Hitachi 500GB HDD, WD 2TB USB 3.0
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ColonelONeill
Posts: 6,293
Registered: ‎12-26-2009
Location: Toronto
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Re: 27++ battery discharge pattern

While the cells will still have charge at "0%", the closer to the reported 0% you drain, the faster the battery wears out. The declared 0% is simply the somewhat arbitrarily determined threshold set in the controller.
W520: i7-2720QM, Q2000M at 1099/688/1377, 22GB RAM, 500GB HDD, FHD screen
TPT1: 1839-23U, stock ICS
X61T: L7500, 3GB RAM, 500GB HDD, XGA screen, Ultrabase
Guru
harrisb
Posts: 1,017
Registered: ‎04-20-2008
Location: Cary, NC
0

Re: 27++ battery discharge pattern

The behavior is normal. There are no settings in the power manger to change the switchover %
W520, i7-2820QM, BIOS 1.41, 1920x1080 FHD, 32 GB RAM, 2000M NVIDIA GPU, Samsung 840 Pro 480GB SSD, Hitachi 1TB 7200rpm HDD, WD 2TB USB 3.0, eSata Plextor PX-LB950UE BluRay

W520, i7-2760QM, BIOS 1.41 1920x1080 FHD, 32 GB RAM, 1000M NVIDIA GPU, Crucial M500 480GB mSata SSD, Hitachi 500GB HDD, WD 2TB USB 3.0
Token Ring
Chatbox
Posts: 486
Registered: ‎11-04-2010
Location: Sydney
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Re: 27++ battery discharge pattern

I wonder if there's a way to submit a feature request to Lenovo...

Or maybe they just want the batteries to wear out quicker...so they can sell more.