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05-21-2009, 01:59 AM

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StoneGod

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Location: Victoria, BC, CANADA

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RE: RE:

Hi everyone. Here is the "NEW" A123/M1 review I've been promising you, and for those of you that don't really want to read the entire review I've provided a summary.

Summary: The new (green plastic sleeve) A123 cells available at www.battlepack.com/a123.asp are of a much higher quality build than the older (white cardboard sleeve) A123 cells that we're all used to getting. Their IRs all meet spec., as do their nominal and peak voltages; however, (here is the BIG bonus) out of over 2700 cells obtained and sold through battlepack.com, they have reported that NONE have been found to be substandard/defective vs. 4-5% of the old version A123 cells. These new cells also appear to be a little lighter (by about 2.5g/ea) than the old M1 cells, and also seem (in my opinion) to solder more easily than the old style cells. Am I happy with these new cells? You bet...and I'll be buying more of them.

When I received the new cells from Battlepack.com, I opened the box and was surprised at the apparent quality of the cells. The lime-green plastic shrink wrap that covered the cells, as a replacement for the old familiar while cardboard sleeves, was flawless, professional, and made me immediately think that these cells where of a higher quality than the old ones.

First up, I tested each cell for its shipped voltage level. ALL eight(8) cells were at exactly 3.31v! That in itself made me wonder if my volt meter was working correctly, so I tested each cell again using my iCharger 1010B+ with the same results - 3.31v!!

The next thing I did was get setup for building my new 4s1p packs. Two 6" pieces of Deans 12 gauge wire (Black and Red), a female Deans connector, and three(3) shorter pieces of Deans wire for connecting the cells. All soldered onto the cells using Novak 3% silver solder.

Soldering the negative pole of A123s has never been very difficult, as they seem to take the heat well...but, soldering the positive pole has always taken more effort than I would otherwise like. The positive pole really sucks up the heat from the iron, and I've always been concerned about damaging the cells due to too much heat transfer causing them to overheat. This issue seems to be solved (or at least much improved) with these new cells. The negative and positive poles soldered up easily using my 80 Watt soldering iron, and very little excess heat was transferred into the cells themselves.

Once I'd finished installing the Deans leads, and connecting the 4 cells together in series, I installed a balance connector and then wrapped the new pack. I then repeated the process with the second pack.

Next up was testing Internal Resistance (IR) of the cells, so I connected the packs to my charger and ran the test. The IRs of the eight(8) new cells were: 8, 8, 10, 10, 11, 10, 11, 11. What does that tell me? Well, compared to my old style cardboard sleeved cells that I bought (supposedly new) off of ebay, these cells have lower IR readings. My old cells ranged from 12 to 14. That said, from a functional perspective I don't expect that there is much difference that would be seen...So, for all intents and purposes, I consider my new cells to be of equal IRs to my old style cells.

Next up was charging! I charge all my A123 cells to 3.65v (balanced) on my iCharger 1010B+. If a cell won't take a full charge, I write the max. voltage that it was able to charge to and put it aside (so I can later match it with other cells of the same max. voltage, and build a pack - at least that allows me to get some use out of them).

These new cells were all at 3.31v to start with, so balancing them shouldn't be an issue at all, but for the first charge - what the heck. So, I hooked up my packs and charged them. All of my new celled charged up to 3.65v without any issues. How does that compare to my last eight(8) cells of the old cardboard sleeve variety that I bought off of ebay? Well, of those eight(8) cells, only 5 would charge to 3.65v; two(2) charged to 3.35v; and one(1) cell wouldn't take a charge at all. In short, these new cells appeared to be head-and-shoulders above my old cells.

Now, having only a small number of old and new style cells, I decided to look into the rate of defective/substandard cells of both varieties. What I learned is that the old style cells (white cardboard sleeves) that we've been buying off of ebay or obtaining from DeWalt battery packs have a defect rate of about 4-5%. Further, these cells are the ones that A123 Systems has for R/C and tool uses.

In contrast, the new (green plastic shrink wrap sleeved) cells are not designated for R/C and tool use. They have the exact same specs. as any A123/M1 cell out there; however, they undergo a more stringent quality control process. From what I've learned from Battlepack.com, they haven't found a single defective cell in all of the new cells they've obtained from A123 Systems...and they've sold over 2700 of these new cells. So, even if I argue that 1:3000 of these new cells will be defective, that still leaves a huge gap in quality between the "old" and "new" M1 cells.

One last point I'd like to mention is their weight. I forgot about weighing the individual cells before I started building with them, because I just figured they'd be the typical 70g/ea. give or take a gram or two...BUT, when I weighed my two(2) new packs and compared their weights to my old packs, my new packs were a full 10g lighter! Could it be the difference between the cardboard sleeves vs. plastic shrink wrap, or is it that my soldering job has gotten THAT much better? Well, I don't think it's my soldering job.

Cheers and happy flying.

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