Today I took apart two different 3rd party battery packs for the 2006-2008  15″ MacBook Pro. The OEM batteries had the following model numbers A1175, MA348, MA348G/A, MA348J/A, MA348*/A.

These packs probably date from early 2010.

NuPower and Lenmar batteries

The first is a Newer Technology NuPower 63Watt Hour Capacity Battery, part # NWTBAP15MBP58RS. There is a barcoded sticker on the outside with the number U091228A11753.

The second is a Lenmar, 10.8v, 60WH/5600 mAh. Model/Part LBMC348.

Superficially they look very similar, but their are some significant differences in their construction.

The NuPower has a relatively thick aluminum plate on the outer surface that is glued to the case. If I recall correctly, this glue failed prematurely and had to be redone. The bottom section of the battery pack is a single piece of plastic, though the back side is painted with a metallic paint to simulate the appearance of the original Apple battery. While this would seem to be a reasonable construction approach, one has to wonder why Apple chose to use a metal back in the first place. A metal back would be thinner than a plastic back, and also transfer heat more readily.

The Lenmar uses a thinner sheet of aluminum for its outer plate. This plate is then adhered to a thin steel sheet that has various bent tabs which catch and latch into the plastic frame of the bottom case. The plastic frame is then glued to a thin steel tray. This is closer to the construction of the original Apple battery pack

Internal view of NuPower and Lenmar battery packs

Once inside, we see a more significant difference in the construction of the two battery packs.

5,600 mAh Lithum polymer pouch cells in NuPower battery pack

Cells from Lenmar battery pack

The NuPower pack, on the left, has a single stack of three 3.7v 5,200 mAh cells. They are labeled as Yoku 3895130, 5,200 mAh/3.7v, BL9120407012749. They measure ~130x95mm and the stack of three is ~11.25mm thick.

The Lenmar pack, on the right, has 3 stacks of pouch cells, each stack is 2 cells deep, connected in parallel. They are labled as YLE 3.7v, ICS594395A280 468061801483. Each pair of cells is ~90x42mm and is also ~11.25mm thick.

I don’t have an original Apple battery around to use in a close comparison, but the Lenmar battery pack construction is much closer to my memory of the stock Apple battery, both in terms of cell configuration, and assembly. I’m still not sure what to make of the absence of a metal back on the NuPower battery. I thought perhaps the Apple and LenMar batteries used the metal back to accommodate a slightly thicker battery, but that doesn’t seem to be the case, since the thickness of the cells in both the Lenmar and NuPower packs is 11.25mm. I don’t know how thick the cells are in an original Apple battery, but I suspect that the metal is there for better heat transfer, and its omission seems like an undesirable bit of cost cutting.

Looking more closely at the cells, I see that Yoku is a battery manufacturer based in Fujian, China. I’m going to guess that the “3895130” gives the dimensions of the cell, 3.8x x95x130mm, which pretty much matches with the dimensions I measured. I don’t know what the remaining number is, but my guess is that it is a manufacturing lot code.

YLE is manufacturer based in Shenzen, China. and ICS594395A280 is a documented part number for a 5.9x43x95mm 2,800 mAh/3.7v cell.

Interesting that the nominal capacity of the Lenmar cells are higher than the cells used in the NuPower, but NuPower claims theirs is a 63 Watt-hour battery, while Lenmar only claims 60 Wh. At this distance though, what I know is that the Lenmar pack is well and truly dead. Two of the parallel packs had voltages ~1v, which is dangerously low. The remaining pair of cells was ~2.6v, which might still be safe to use, though I’d have to put it through testing to see how much of the rated capacity remains. The NuPower still works, and the cells were at something close to 3.7v each. The estimated capacity of the pack, as reported by System Information, is quite low though, perhaps 50% of original, which is why I decided to tear it open in the first place.

I’m not sure what I’m going to do next, other than recycling the low cells. I’ll probably set the good cells aside until I get a hobby charger that I can use to analyze them and decide whether they are worth keeping to power misc projects.

I’m also going to look into buying replacement cells and rebuilding the packs, provided that the price is right and the seller is reputable. I could just order a replacement for the whole pack, but I’d be a bit concerned about getting old stock at this late date.