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802.11n
Posts: 508
Registered: ‎11-04-2010
Location: Sydney
Message 1 of 7 (900 Views)

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++?

Guru
Posts: 1,506
Registered: ‎04-20-2008
Location: US
Message 2 of 7 (891 Views)

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.


P70 XEON 1505, BIOS 2.08, UHD 4k Display, 64GB non-ECC RAM, M3000M NVIDIA GPU, RAID 1 512GB Samsung 951 PCIe-NVMe SSD x 2, 2x Samsung 850 Pro 1TB SSD. EM7455 WWAN

T460s, BIOS 1.15, WQHD display, 20GB RAM, I7-6600U, Samsung PM961 1TB PCIe-NVMe SSD, EM7455 WWAN
802.11n
Posts: 508
Registered: ‎11-04-2010
Location: Sydney
Message 3 of 7 (888 Views)

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
Posts: 1,506
Registered: ‎04-20-2008
Location: US
Message 4 of 7 (872 Views)

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.


P70 XEON 1505, BIOS 2.08, UHD 4k Display, 64GB non-ECC RAM, M3000M NVIDIA GPU, RAID 1 512GB Samsung 951 PCIe-NVMe SSD x 2, 2x Samsung 850 Pro 1TB SSD. EM7455 WWAN

T460s, BIOS 1.15, WQHD display, 20GB RAM, I7-6600U, Samsung PM961 1TB PCIe-NVMe SSD, EM7455 WWAN
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Guru
Posts: 9,240
Registered: ‎12-26-2009
Location: Toronto, Canada
Message 5 of 7 (865 Views)

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: 2720QM, Q2000M at 1082/1376, 32GB RAM, 500GB + 750GB HDD, FHD screen & MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 160GB HDD, WXGA+ screen
TPT1: 1839-23U
Guru
Posts: 1,506
Registered: ‎04-20-2008
Location: US
Message 6 of 7 (860 Views)

Re: 27++ battery discharge pattern

The behavior is normal. There are no settings in the power manger to change the switchover %

P70 XEON 1505, BIOS 2.08, UHD 4k Display, 64GB non-ECC RAM, M3000M NVIDIA GPU, RAID 1 512GB Samsung 951 PCIe-NVMe SSD x 2, 2x Samsung 850 Pro 1TB SSD. EM7455 WWAN

T460s, BIOS 1.15, WQHD display, 20GB RAM, I7-6600U, Samsung PM961 1TB PCIe-NVMe SSD, EM7455 WWAN
802.11n
Posts: 508
Registered: ‎11-04-2010
Location: Sydney
Message 7 of 7 (821 Views)

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.

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