Hi Luke,
liveforphysics said:
The .PDF from A123 said the 20Ah pouches are made in Korea.
These A123 pouches Lynchy is getting say made in Korea.
The only mention of Korea, so far in this thread is the picture from the Chinese sellor's picture on Alibaba. They could have obtained that the picture from the Web or from the pdf we downloaded.
To quote Jeff's response from A123:
"
Hi Jeff,
Thank you for bringing this to my attention. This cell is not available for quantity sale and I question if the cells that are being marketed are knock-offs or stolen.
We manufacture the prismatic cell in Korea , so I don't know how they could find their way to a china reseller....
Believe me, I have multiple projects that require this cell but it is on strict allocation for key automotive customers. If I can't get them, I don't know how this dealer can.
Best,
xxxxxx
"
liveforphysics said:
The grounds for them being fakes is based on some minimum wage PR email responding lady telling Jeff that she doesn't know how A123 cells would get to China from Korea?
Probably not a minimum wage PR lady. Jeff built this very nice ev with 3,360 M1 cells, purchased directly from A123:
http://www.evalbum.com/2621
3360 A123 Systems M1, 3.20 Volt, Lithium-Ion
Thirty cell parallel clusters, arranged as four series wired clusters in each battery module. A total of 28 series wired battery modules power this vehicle. Usable battery capacity: 23kW hrs.
In response to a question he said he purchased them directly from A123. He might have purchased a pallet. He said he got an excellent price but had to sign an NDA on pricing and agree not to use them in power tools and (I think) agree not to sell bare cells. After he built his pack he sold his welder on the ES sales forum, I think to John Holmes.
At work, I've bought 200million dollars of servers from HP. I still never had an email answered by anyone that has a clue WTF is going on. lol
liveforphysics said:
Furthermore, in the .PDF from A123, on page 33 where it lists:
3. First massâ€Âproduced HEV in China (Shanghai Automotive, largest OEM in China) to use A123cells"
…this leaves China as having the first EV produced with A123 cells. This tells me the odds are pretty damn good that at some point cells go from A123's point of origin in Korea to China, no matter what some lady paid to answer emails from the public happens to think/guess. China is like the wild west. We know they are getting cells, as China has A123's only successful production level EV application. If China is getting the cells, it's like the wild-west over there, cells are in the country, you're going to see people selling the cells. They bought millions of the 26650 A123 cells for cheap under an agreement to only supply them to OEMs, and of course they end up selling them on E-bay, alibaba, etc straight to us EV tinkerers. We know they are getting supplied with EV sized cells from Korea, why do we think it would be impossible that they are selling them openly as well?
Excellent point about the possibility of A123 cells being available in China.
Yep, we know the cells are in China, A123 acknowledges that.
liveforphysics said:
The folks on here looking for peak performance will want to run the packs at 26s to give them ~100v peak. All the power hungry hubmotor guys (and the few RC motor guys with sensors mounted, like myself) run 100v.
The RC motor guys will want to run 13s, as 50v is the limit of 99% of the HV RC controllers on the market.
Gary recommends using 12s for 36v and 16s for 48v packs as this allows the use of relatively inexpensive SLA Chargers (if you have a BMS). So 12s and 16s packs that could easily be connected (doubled) in series would take care of 36v, 48v, 72v and 96v if the 100v controllers can handle 3.7v (118v for 32s) per cell hot off the charger with 3.3v (106v for 32s) nominal (the M1 cells drop almost immediately to their nominal voltage of 3.3, then stay there until they are almost dead).
All the RC controllers that have 50V caps on them aren't going to want to see more than 13cells. A couple of RC controllers run 63v caps. Same with an IRF4110 modded controller like a Methy special, or an Infinion. If you run over 26-27 cells, you're not going to be able to connect your charged pack to your controller without risking damage. You could run more in series, but then you're making a 17-18Ah pack rather than a 20Ah pack, because you won't be able to fully charge them. You could do this if you have a BMS/charger setup to only charge them so far.
The Castle HV series run fine on 15s but 16s kills them.
lynchy said:
I will do my best to offer these at a fair and competitive price. However after some thought I am tending towards the idea of doing these cells as completed packs, with BMS and in a proper case. These cells are a bit special and to be honest they are not for everyone.
The main advantages (IMO) over M1 cells are the ease in pack building. If they are not available as bare cells and they require compression I don't see the advantage as compared to M1 cells which are currently about $6 per cell. I'd be concerned about flat cells compressed against each other overheating.
With a 30C rated cell, you can very safely put that fear to rest my friend. Ri in the 0.5-0.8mOhm/cell area puts thermal concerns on the cells at zilch. Even continuous 200amp continous loads would be making just 32w of heat at the cell for 6 minutes... aka, 11.5KJ. I couldn't turn up a specific heat constant for a LiFePO4 polymer battery, but we know it's somewhere inside the range of solid materials between graphite 0.710KJ/Kg-C and the greatest specific heat solid material on earth, Lithium metal, at 3.58KJ/Kg-C. This gives boundaries on a worst possible case temp rise of 24.25c (if the cell were solid graphite) to 4.81c (if the cell were pure lithium). This is assuming the cell is just continuously discharged at 200amps in a vacuum with all energy kept in the cell, absolutely zero thermal energy loss. Even in a worst case scenario, if the cell was pure graphite (which is actually worse than even if it were pure styrofoam lol), then you're still going to end up below the 70deg C operating range temp for the cells.
Rest your thermal concerns my friend
For a BMS you might want to consider Gary and Richard's (Goodrum and Fechter) BMS:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416
Another option that wouldn't have an 80a limit would be packs with Cell Monitors, like the following, configure to work with RC balancing chargers:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=12815
CellLog 8S battery monitor and logger - any reviews?
Great little device for monitoring cells.
Features include,
Bar graph display,
0.001V display,
Various configable alarms, including cell low voltage alarm,
Alarm port ( cutout for throttle or controller?),
and can log voltages for each cell.