Note: There is a report that cells from this pack came out with a voltage of 1.7-1.9v. New cells at this level pre-charged at 50-100mAh for a few minutes until they reach 3v before charging can have a good useful life, but you should keep an eye on them during charging. They should get to 3v within 10 minutes or so, and shouldn’t heat up significantly during charging. Once charged, check the voltage after a few days and make sure they aren’t lower than 4.1v or so.
Over on Ebay, Red Planet Trading is selling Dell 9 cell, 80Wh, 7200mAh battery packs for $14.99 with free shipping. They currently show more than 10 available.
The pack is labeled that the cells are made in Korea, which means Samsung, of LG. Capacity is probably 2,400-2,500 mAh/cell.
This isn’t the pack to tear down if you are looking for high capacity cells, but at $1.66/cell and $0.19/Wh, its a good value.
Looks like the same pack is listed a few different ways:
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.
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.