Tag Archives: battery

The humble Smart Battery reveals its secrets

It took me a little longer than I’d hoped, but I’m able to get most of the information I want out of most of the laptop batteries I’ve tested.

ASUS AL32-1005

Manufacturer Name: AS085NJ35E
Device Name: 1005-28
Chemistry LGC0
Design Capacity (mAh): 5400
Design Voltage: 11250
Manufacture Date (Y-M-D): 2009-6-21
Serial Number: 937
Specification Info: 49
Cycle Count: 254
Voltage: 10.28
Full Charge Capacity (mAh): 1680
Remaining Capacity (mAh): 0
Relative Charge PCT: 0
Absolute Charge: 0
Minutes remaining for full charge: -1
Cell 1 Voltage: 2642
Cell 2 Voltage: 3820
Cell 3 Voltage: 3817
Cell 4 Voltage: 0
State of Health: 0
Charging Current: 0
Charging Voltage: 0
Temp: 20.25
Current (mA): 0

You’ll see that this pack is 5 years old, and has had 254 cycles, which probably puts it near the end of its useful life. Looking at the individual cell voltages (actually banks of parallel cells), you’ll see that that one of them is quite a bit lower than the others, suggesting those cells are closer to failing.
I’m still having trouble with the Dell packs I’ve tested. I can get most of the information I want from them, but they don’t report the capacity of the individual cells properly. The individual cell data isn’t part of the official smart battery standard, but it seems pretty standardized. It may be the Dell packs don’t report that information at all, or it may be that they use a different set of commands to reveal it.

Dell 9T48V

Dell 9T48V
Manufacturer Name: SMP-SDI2.8
Device Name: DELL YXVK234J
Chemistry LION
Design Capacity (mAh): 8400
Design Voltage: 11100
Manufacture Date (Y-M-D): 2013-4-19
Serial Number: 181
Specification Info: 49
Cycle Count: 44
Voltage: 10.03
Full Charge Capacity (mAh): 8428
Remaining Capacity (mAh): 0
Relative Charge PCT: 0
Absolute Charge: 0
Minutes remaining for full charge: -1
Cell 1 Voltage: -1
Cell 2 Voltage: -1
Cell 3 Voltage: -1
Cell 4 Voltage: -1
State of Health: -1
Charging Current: 4214
Charging Voltage: 12900
Temp: 23.25
Current (mA): 0

HP Packs have been a mixed bag. I’ve been able to get a full compliment of data out of some of them, and none at all out of others. I’ll work on fixing it after the initial release.

The code runs on an arduino Yun now, and should be easily adapted to any arduino compatible. I’m going to write a little documentation and release it while I continue to work on it.  If you are interested in getting early access, leave a comment here.

Acer AS11B5E (4INR 18/65-2) 14.8v 6000 mAh 84wH Battery Pack Teardown

I’ve been trying to get my hands on some higher capacity cells than the 2,600 mAh Samsung cells I’ve accumulated so many of, so I’ve been looking through ebay listings for reasonably priced new  battery packs and then checking the photos, descriptions, and even the web for specs and other information that will help me figure out whats inside.

I recently ordered a Acer AS11B5E (4INR 18/65-2) battery pack fro $21.99 with free shipping from In And Out Electronics. They shipped it out quickly and I received it today.


As you can see, its not like most packs made with 18650 cells. Rather than a tough case with connectors and latches for easy installation and removal, this pack has a thin flexible case ribbon cable with a connector. Its clearly meant to be an internal battery that isn’t swapped, but replaced when it wears out. This has been Apple’s approach for about 6 years now, but Acer is using standard 18650 cells, while apple is using custom sized pouch cells.

Apparently the laptop this was designed to power was an absolutely huge media laptop with a 18.5″ display. Crazy!


This pack was incredibly easy to open! .Getting the batteries out of most packs is like shelling a crab, or getting the meat out of a ripe coconut, this was like shelling shrimp, or a soft-shell crab. I just had to pull off strips of tape to get to the sweet sweet battery meat inside.


Look at those juicy cells!  Those are Panasonic NCR18650A cells with a nominal 3,100 mAh capacity! Even better than I expected, and I’ve got 8 of them!

I was hoping for 2,800 or 2,900 mAh cells, based on the specs for the pack that I was able to find which rated it at 14.8v and 84Wh, so the extra nominal capacity was a nice surprise. I’m not sure the source of the discrepancy though. It could simply be that Acer derates the cells slightly.

Another explanation is that these cells tolerate discharges down to 2.5v (most cells should only be discharged down to ~3v) but the capacity between 3v and 2.5v is less than 10% of the total. From the specs for Panasonic NCR18650A cells, it looks like the capacity is ~2,950 mAh if you only discharge to 3v. Avoiding maximum discharge also increases the useful life of the cell.

In any case, in retrospect, some of the clues were there before I opened the pack.


  • 4INR18/65-2: A series of four cells 18mm in diameter and 65mm long (aka 18650), with two cells in parallel.
  • 14.8v: 4 cells in a series works out to a nominal cell voltage of 3.7v (panasonic actually lists 3.6 as the nominal cell voltage for these batteries, but I think thats because of the discharge profile that reaches lower voltage than typical for cells of this chemistry).
  • Panasonic P/N : NCR-B819: This suggests that the pack is manufactured by Panasonic, and so not a surprise that it includes panasonic cells.

Once I had the pack apart, I checked the voltage and found that it only measured 7.8 volts or so, or a bit under 2v for an individual cell. With ordinary lithium ion batteries, that would be a worryingly low voltage. I’m hoping that its less of an issue with these cells. I immediately applied a low charging current (200mA) to bring the pack up to ~3V.


It appears to me that this pack was manufactured in June of 2011, or a bit over 3 years ago. Thats a long time to sit without being recharged, though I’ve had older packs that have discharged less.

I’m keeping the circuitry of the pack intact so I can try to read out information from the battery management board. Once I’ve done that, I’ll put these cells through a few charge/discharge cycles and see how they perform.

Notes: Smart Battery Hacking 2014-08-27

I’m trying to read out information from three different laptop batteries by taking advantage of the smart battery system interface.

The batteries are:

So far, I haven’t had any success in reading out data from any of the batteries, but I have figured out the pinout of the connectors:

MacBook Pro Battery ConnectorIMG_6028

From left to right, inside the wide guide slots on either side:

  • P-
  • Temperature
  • Data (SMBus)
  • Clock (SMBus)
  • Unused
  • P+

 Acer Battery Connector


From left to right, inside the wide guide slots on either side:

  • P-
  • P-
  • Data (SMBus)
  • Clock (SMBus)
  • Temperature
  • Battery Activate / Enable
  • P+
  • P+

The MacBook Pro battery packs make power available all the time, while the acer batteries require a short or low resistance connection between the P- (system ground) and the Battery Activate pin in order to “wake” the battery so it will present voltage, or receive charging current. Furthermore, the Acer packs only wake up briefly if the overall pack voltage is below ~9v or so.

I’m currently using an arduino and using this post as a starting point on how to (try) to talk to a smart battery.