I don't think A123Systems is being completely honest about the "B" grade or clone cells. Some of what they have told us has not been factual. It may be posturing to keep the price and apparent value or their product high. Caution and testing as you are doing is excellent. Thanks for doing it!
Toolman did get a good looking sample. His was made in USA, too if I recall correctly. I think when you order just one cell for testing you are pretty sure to get an unblemished sample. That's why I wanted to test a large batch. I'm showing the worst ones in these photos. There's really only 2 out of the 30 that look like the tabs have been touched. We'll see what the testing tells us.
EDIT: Actually, it was webfootguy who got a cell labeled made in USA from a123rc. Toolman's was made in korea. Interestingly, several of mine have the same lot number and batch code as webfootguy's but are labeled made in korea.
I live in Michigan. A123 has locations in Livonia, and Ann Arbor. I recently applied for a quality control position at their Livonia location.
Hopefully they hire me and offer me loads of free cells. Probably not, but maybe at least a discount of sorts. Their Livonia office is right next to a 40 mile bike path.
If they hire me, I can afford their batteries. Oh the irony.
Don't know the price they'll put on the cells, but here you go guys:
http://www.mavizen.com/
They might even be willing to sell to the DIY crowd as this is what was said in Autoblog:
"Mavizen isn't limiting sales to bike builders though. They're about to ship 1,000 cells that we're told are for a non-motorcycle application with more in the works."
Finally got my CBA III and will do some testing this weekend and make an attempt to build a 48v20AH pack. I'll post pictures as I go.
I also got a story from the supplier about where this batch of cells came from. Apparently, they bought them from an electric vehicle company that had built them into packs but decided not to go with that design. The tabs have the unusual perforations and slightly shorter tabs as a result of having been built into the packs. So, supposedly, these are A-grade cells that are being sold as B-grade because of their previous handling. If that is true, then these are not the same source as a123rc is selling, although they do have the same lot number, batch number and "made in Korea" stamp as what toolman showed.
Did some intial testing today on my favorite cell, which I shall name Bob. Recall that Bob is the one that took a beating during shipping (see picture above). I charged Bob 10 days ago on a single cell charger to 3.6v. Today, it was still holding onto its charge at 3.56v. Just to see how much abuse these cells can take, I mashed Bob flat and smoothed its surface with a wooden dowel. I was suprised how well this method improved the look of the cell. Now it looks as good as the undamaged cells. Voltage, still checking good at 3.56.
My new CBA III arrived yesterday, so I used Bob as the test dummy for an easy 1C discharge rate of 20 amps. First thing I learned is how important it is to make good connections at the tabs. My cheesy copper spring clamps allowed a 0.15v voltage drop during most of the test. You can see on the graph where I messed with the connection by adding clamps to up the connection pressure, but to no avail. I'll work on a better clamping system before I up the amps with an additional resistive load. For now, though, you can see that old Bob delivered a solid 19.65 amp hours with a nice flat discharge curve. Accounting for the losses due to my poor connection system, it looks pretty clear that Bob was able to hold onto his full 20Ah over the 10 days since he was last charged. Way to go Bob!
High-amp tests to come as soon as I finish building a load and Bob gets a well-deserved recharge.
The flat discharge curve is the best thing about these cells. I'll test several more in the coming days. BTW, I like the new avatar---Blacky McLaser Eyes?
Good, i'd like to see these tests.
My avatar is a modified version of the energizer battery cat logo; i made it for use on my battery box and figured it'd be appropriate for ES too.
I bought 2 cells for $40.99 each (with free shipping) at a123rc.com. Price has since gone up to $59.99 each. My cells appear to have come from the new plant in Michigan as they have "Made in the USA" printed on them and appear new (no marks on the tabs or on the cells).
Yes, that was me trying to put more pressure on the terminal connections with more clamping force. There was a 0.15v drop between the terminals and the CBA due to not-so-great connection.
Working on it, Travis. This 1C test was just to debug the setup and check for total capacity . Should have some 5C or higher results to post later in the week. I can't afford a CBA amplifier so will have to use a resistive load in parallel with the CBA and calculate the added current---if the discharge curve is relatively flat, I should be able to get a good approximation of total current load by monitoring the voltage drop across the resistors. I imagine results will look like the earlier test you posted, at least I hope they will.
An auction for 8 20 Ah cells just showed up on ebay. Seller has zero feedback and is based in China. The cells have the tabs cut off but so far the price is right if someone wants to try to get some cells cheap.
An auction for 8 20 Ah cells just showed up on ebay. Seller has zero feedback and is based in China. The cells have the tabs cut off but so far the price is right if someone wants to try to get some cells cheap.
Wow, those tabs are completely cut. Interesting that he only rates them as 3C continous. Probably because you can't get a higher current termination. Price is definitely right when you factor in free shipping. Now if he only had 16 of them you could build a complete battery.
I finished making a resistive load and some aluminum clamps for the terminations today. Then I tested two more of the cells. Cell 1 at 25amps on CBA plus 40 amps on the load for 65 amps total. Cell 2 at 20 amps on the CBA plus 53 amps on the load for 73 amps total. Both cells stayed flat above 3.1 v until about 17 ah expended, then slow dropping until 2.0v test cutoff.
I need to add more power resistors in parallel to get the load over 100 amps, but so far these cells are looking strong. I'm satisfied enough for now to start building a battery. I just bought a new Crystallyte HS motor with 45 amp controller and these cells can certainly handle that kind of discharge. So far it looks like these cells are only limited by the quality of the terminations, so that will be my next battle.
A company has announced a reseller agreement with A123Systems for the 20Ah prismatic cells! And they will offer warranty support and intend to offer all the other A123 cells as well. This is great news as far as I am concerned.
I submitted a request for AMP20 Prismatic Pouch Cells a few days back, no response yet, has anyone else submitted a request here?
http://www.mavizen.com/contact.html
rant-mode
I find the story with batteries sickening. Just about in every other area of business you can get industrial grade materials and components in sample or small business quantities freely and legally via distributors (and this includes hazmat-grade stuff, that can burn, poison or cut parts of your body and/or damage your property). This is considered normal in terms of risk/reward for the society. But somehow if we want modern raw cells from any premium manufacturer we have to go through gray channels (and getting QC rejects, cells from disassembled packs and who knows what) as if we are buying drugs or something... This situation really kills innovation in the world of EV and the innovation is normally done in startups, not big companies.
/rant-mode
