Battery Deal: Genuine Dell Battery Inspiron 13R N7010 N5010 N4010 9T48V M511R GK2X6 | eBay

I ordered one of these “Genuine Dell Battery Inspiron 13R N7010 N5010 N4010 9T48V M511R GK2X6” from eBay seller for $17.99 and free shipping. Its a 9 cell, 90Wh pack, which, I estimate, probably has 2,800 mAh cells. It arrived quickly and was packed well, but I haven’t opened it yet.

Works out to be $2/cell and $0.19/Wh, which is a pretty good deal.

There are a couple of downsides though. The pack I got had ~40 cycles on it. Not bad, but probably 10% of the lifespan. It wasn’t a surprise either, since the pack wasn’t described as new, it was listed as manufacturer refurbished.

Which brings me to the second problem. Before purchasing, I asked the seller for more information about what “manufacturer refurbished” meant and they didn’t reply. After purchasing and receiving the pack, and checking the cycle count, I decided that it would be worthwhile to get another couple of packs if I could get them at a lower price, so I took advantage of the “Make Offer” featured on the listing and offered a lower, but still reasonable price for two. They ignored the offer and let it expire.

Battery Deal: Acer AS09D70 5600mAh 11.1v battery pack

I found a seller with a decent price on a few Acer AS09D70 5,600mAh battery packs on ebay.

These appear to be new, old-stock, packs. The listing has conflicting information. The title states they are 5,600 mAh and 56wH, which doesn’t quite make sense, since the nominal capacity is 11.1v. The listing explicitly states 4,000 mAh capacity, but the pack markings in the listing look like 5,600 mAh.

Someone cracked one of these packs one of these packs open, and found six Samsung 18650-28As, which are 2,800 mAh cells, which make these  62Wh.

The seller has these for $16 with free shipping, which works out to $2.66/cell. That also works out to  $0.26/Wh which isn’t bad, though I’ve seen $12 packs with 6 2,600 mAh that are a bit better deal.

One caveat is that these cells are supposed to be charged to 4.3v. Typical Lithium Ion chargers charge to 4.2v. If you charge to 4.2v, you’ll give up a bit of capacity.


Tips for identifying battery packs with high capacity cells

If you are interested in finding laptop battery packs with high capacity cells on ebay, it helps to know that government regulations require that battery packs with more than 100wH of capacity need to be transported as hazardous materials. Needless to say, no manufacturer sells battery packs with more than 100wH capacity.

The 100wH limit places an upper bound on the number of cells in a pack, and their overall capacity.

In the past, companies sold 12 cell packs. Those packs might seem like a great source of cells, but keep in mind that the cells won’t have more than ~2,300 mAh nameplate capacity. Actual capacity could be even lower, because 12 cell packs are probably more than 5 years old.

Improved energy densities mean that extended packs are now more likely to have 9 cells. A 9 cell pack at the 100Wh limit will have cells with ~3,000-3,100mAh capacity.

If you want cells with more than 3,000 to 3,100 mAh capacity, you’ll have to look at 8 or 6 cell packs. The best cells 18650 available today have a capacity of 3,200-3,400mAh. An 8 cell pack with such cells would be in the 95-100wH range. A 6 cell pack with such cells would come in at ~75wH.

I haven’t come across any packs in this range, but I’m also focusing my attention on packs that work out to $2-3/cell, which pretty much rules out anything using the latest and greatest cell technology.

So, bottom line, if you are looking for 3,000 mAh cells, you need to confine your search to packs with 9 cells or fewer. If you are looking for 3,200-3,400 mAh cells, you’ll need to narrow your search further to packs with 8 cells or fewer. Happy hunting!

Smart Battery Hacking Progress!

I finally made some progress on reading out data using the “smart battery” interface on laptop battery packs. I’ve succeeded in pulling a number of useful numerical values from three different MacBook Pro batteries from two different manufacturers and one Acer battery pack. I have, so far, failed to get anything out of a different model of Acer pack, an ASUS pack, and an HP pack, but I have some ideas about what to try next. I also have to do more work to make sense of a few of the values I’m getting, and figure out how to read out string data, and figure out if I can get at voltages for individual parallel banks of cells.

In the meantime, here is what I got out of an old Mac battery:

Design Capacity (mAh): 5800
Design Voltage: 10800
Manufacture Date: 15400
Cycle Count: 531
Voltage: 12.23
Full Charge Capacity (mAh): 3073
Remaining Capacity (mAh): 2812
Relative Charge PCT: 92
Absolute Charge: 48
Temp: 31.85
Current (mA): 0
Minutes remaining for full charge: -1

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.

Inside look at HP’s approach to laptop batteries (circa 2012)

While trying to find details of what’s inside HPs extended runtime batteries, I came across video shot by Tom’s hardware of a press junket / meet-and-greet with Dr. John Wozniak from HP talking about what goes into designing and HP’s battery packs.

It’s from spring of 2012, which makes it a bit dated in some regards, but I still found it informative, particularly since most of the battery packs I’m getting are of a similar vintage.

Some things I found interesting:

  • Relative to 18650 cells, prismatic LiIon are ~1.4x more expensive, and pouch packs are 2x more expensive for the same capacity.
  • At the time, 18650 cells were clearly HPs focus for price/capacity. They were, however, using prismatic cells and pouch-packs for thinner form factors.
  • Pouch cells are relatively easy to get 1000 charge cycles from because they can expand and contract as needed when being charged and discharged, reducing the pressure that degrades the electrodes. The downside is that cells can also expand due to gas generation, which can damage the pack and/or other components.
  • At least for the products being discussed, HP seemed to be transitioning from prismatics to pouch packs.
  • Safety regulations limit companies from stuffing more than 100Wh into a single battery pack. This, combined with improved capacities, have lead to the demise of 12-cell extended runtime packs.
  • At the time, HP was using LG 3000 mAh cells for their high-capacity 18650 packs.
  • Apple shouldered the growing-pains of getting pouch-cell pack design and manufacturing right.
  • Because the cells are a commodity, HP tries to distinguish its packs on quality, reliability and manufacturability. This has led them to use conformal coatings on circuit boards to protect against shorts and corrosion. They’ve also switched from wires to flex circuits within the packs for improved reliability and their pouch-cell packs have moved to welding the cell contacts directly to a PCB.
  • Their primary suppliers are Panasonic, LG, Samsung.
  • Among Chinese cell manufacturers, they’ve tried to work with a few, but the economics haven’t worked out. B&K is a qualified supplier for some of their packs, but HP doesn’t ship many of their cells.

HP TD06 (Series HSTNN-UB85) 11.1V 62Wh battery pack teardown

I picked this HP TD06 (Series HSTNN-UB85) 11.1V 62Wh battery pack up at RePC for $1 at the same time I got the ASUS AL32-1005 pack I posted about earlier. Based on the nameplate pack voltage, it was one of only a handful that used newer 3.7v lithium ion cells out of the hundred or more packs they had.


It was also the only of TD06 pack using newer cells; there were 3-4 labeled with a 10.8v voltage.

Peeling the label back gave a tiny peak at the cells. I was able to separate the two halves of the pack case with a thin bade, pliers and a bit of elbow grease.


The lavender-wrapped cells are clearly made by Samsung (not a big surprised, given that the pack label indicated that the cells were made in Korea. The remaining marking is ICR18650-28A. These cells are rated for 2800 mAh of charge capacity, which isn’t a surprise given the 62Wh claim. Unfortunately, they must be charged to 4.3V to achieve that capacity. When charged to the more common 4.2V, they have about 7.5% less capacity.

The battery management seems to be divided between two chips with a lot of pins.  One is labeled M37512, FC024, J2C5D. The other is 20020 ??05. The first chip appears to be an 8-bit M37512-FC MCU from Renesas intended for…battery pack applications. I’m not sure what the second chip appears to be a RS20020. This is a companion chip for battery pack applications. I can’t find information on what it does, exactly, but it seems to have connections to each cell, and to the MOSFETs that can switch the flow of current to or from the pack on and off.

ASUS AL32-1005 11.25V 5600mAh 63Wh battery pack teardown

I picked this ASUS AL32-1005 11.25V 5600mAh 63Wh up at RePC for $1. Based on the nameplate pack voltage, it was one of only a handful that used newer 3.7v lithium ion cells out of the hundred or more packs they had.



Labels for the positive and negative contacts were, helpfully, molded into the plastic.


Removing the plastic sticker exposed part of the cells, but to get them out, I had to rip the plastic case apart, with some pliers and elbow grease. Pack voltage is reasonable, so its unlikely that any of the cells are completely shot, but at the point, I don’t know how much use they’ve suffered. I’m leaving the circuit intact for now so I can try and read out the smart battery information so I can see if there is any correlation between that and the results of testing the individual cells.

The cells themselves look like they are made by LG. They are all labelled LGDC118650. All the onces I can see also have I1245xxxxxx, MED45DxC1, where the ‘x’ represents a position with a number or letter that varies from cell to cell.

From what I can tell, the manufacturer is LG, and they are 3.7V, 2,800mAh cells, which is pretty much what I expected based on the specs printed on the outside. One of the only english-language pages I found mentioning these cells suggested they had a charge termination voltage of 4.35v, but I’ve found nothing else to corroborate that.

The battery management chip is labeled bq 20Z45, 95K, CP7L, which looks like the TI bq20z45, an all-in-one battery management chip.