New A123 Prismatic 20Ah cells 480g and 30C
- Thread starter lynchy
- Start date
cell_man
100 kW
More pics of 15Ah cells 
HI, I'm a long time lurker, this is my first post here. I have been trying to buy A123 cells for a long time. I've been driving on PbA packs for years, and it's time for replacement again. And now I saw the thread about prismatic cells being available. Wow.
The last real update was back on Dec 13 (a month ago) and since then... nothing.
One of the posters was really trashing on A123 cells in his other threads, and now he's in on buying samples
I sure hope the guys buying the A123 cell samples aren't being suckered.
The last real update was back on Dec 13 (a month ago) and since then... nothing.
One of the posters was really trashing on A123 cells in his other threads, and now he's in on buying samples
I sure hope the guys buying the A123 cell samples aren't being suckered.
liveforphysics
100 TW
No getting suckered here 
These cells are fantastic! It's like the weight and performance of LiPo, but with an extreme cycle life, and a safety chemistry.
The A123 cells that get made fun of are the 26650's, which require elaborate pack building processes, and have crappy energy density compared with LiPo or these cells.
These cells are fantastic! It's like the weight and performance of LiPo, but with an extreme cycle life, and a safety chemistry. The A123 cells that get made fun of are the 26650's, which require elaborate pack building processes, and have crappy energy density compared with LiPo or these cells.
so another silent month passes by on possibly the biggest leap forward for ev batteries ?
they have been out for a good few months now, and i cant yet find any test of capacity for the 20ah type (just at say 40a or so) or am i just looking in the wrong place?
your work (luke etc) with 400a is gold dont get me wrong, but many a cell that ive seen can take that (20c that is) for maby 10 cycles before turning into sausages..
i know that 26650 a123s are the toughest cells around, and your info on the prismatics has helped me to invest in them but these are from the first batch and
it just makes me i little nervous about the wad of these cells that i have committed to buy, when it all goes so quiet?
please just make the bad dreams about my new big dollar sausages stop.. :wink:
they have been out for a good few months now, and i cant yet find any test of capacity for the 20ah type (just at say 40a or so) or am i just looking in the wrong place?
your work (luke etc) with 400a is gold dont get me wrong, but many a cell that ive seen can take that (20c that is) for maby 10 cycles before turning into sausages..
i know that 26650 a123s are the toughest cells around, and your info on the prismatics has helped me to invest in them but these are from the first batch and
it just makes me i little nervous about the wad of these cells that i have committed to buy, when it all goes so quiet?
please just make the bad dreams about my new big dollar sausages stop.. :wink:
johnrobholmes
10 MW
search for "cell man"
yep, thanks, i did that and theres plenty of info from cellman about building packs etc and he said the 15ah are actually 16ah, but nothing more recent about the 20ah cells like actual capacity over a good few cycles or discharge curves (even at low c rates).
i have faith, i really do (in the a123 goodness), but i cant help but observe the 70% + disappointment that i have generally seen in long term use of many types of cells over the years.
haveing said that i will lay the cash out again for these cells, and do some tests of my own soon, but surely there's a bit more info from people out there somewhere?
i have faith, i really do (in the a123 goodness), but i cant help but observe the 70% + disappointment that i have generally seen in long term use of many types of cells over the years.
haveing said that i will lay the cash out again for these cells, and do some tests of my own soon, but surely there's a bit more info from people out there somewhere?
cell_man
100 kW
Here are some graphs of independent tests done by Rod Dilkes. You can see discharge at 140A or 7C and also a comparison with some other battery types at 3C where the 20Ah cells were 2p and compared to Thundersky 40Ah and Sky Energy 40Ah.
View attachment Rod Dilkes Test.JPG
View attachment Rod Dilkes Test.JPG
markcycle
10 kW
This is directed to cell_man
I it possible for you to set up a web page that I could direct my customers to. You have a great battery but my customers want to see a web page and not buy just from information off a fourm thread.
Thanks
Mark
I it possible for you to set up a web page that I could direct my customers to. You have a great battery but my customers want to see a web page and not buy just from information off a fourm thread.
Thanks
Mark
cell_man
100 kW
Hi Mark,
I am really sorry that I haven't sorted a website out yet. I know that should have been a top priority but it's been so hectic trying to sort out so many different things that I haven't got round to it so far. I've actually got a few domain names and a basic hosting package that I bought some time back. I've got a long list of excuses why I haven't done it but it really doesn't count for much. I do apreciate you spelling it out so clearly and I'll try to get something sorted soon ok.
Thanks
Paul
I am really sorry that I haven't sorted a website out yet. I know that should have been a top priority but it's been so hectic trying to sort out so many different things that I haven't got round to it so far. I've actually got a few domain names and a basic hosting package that I bought some time back. I've got a long list of excuses why I haven't done it but it really doesn't count for much. I do apreciate you spelling it out so clearly and I'll try to get something sorted soon ok.
Thanks
Paul
good to see the west mountain graph with a real 20.0ah capacity, but it indicates about 4.2m ohms internal resistance and this (at 140a) would have the cell dissipating 70 watts of heat -am i wrong in thinking that would take it well above 36deg c ?
its a fair thing i reckon that when you load a cell to the point where you lose 10% of its energy to heat (due to ir), then that should be the maximum c-rate for that cell -afterall we are not keen to lose 10% of our motor efficiency.
for this cell in this test, its lost .5 of a volt at 140a (giveing away 17% to heat) and that tells me its not really capable of 8c,
BUT my money is on luke here with his reading of .821m ohm ir giving us a massive 17c and 352a at around the 10% loss point.
kinda seems like the west mountain test doesnt add up right, maby he wasnt testing the voltage right at the cell tabs or something -easy to miss a few tenths of a volt at these amps i spose.
its a fair thing i reckon that when you load a cell to the point where you lose 10% of its energy to heat (due to ir), then that should be the maximum c-rate for that cell -afterall we are not keen to lose 10% of our motor efficiency.
for this cell in this test, its lost .5 of a volt at 140a (giveing away 17% to heat) and that tells me its not really capable of 8c,
BUT my money is on luke here with his reading of .821m ohm ir giving us a massive 17c and 352a at around the 10% loss point.
kinda seems like the west mountain test doesnt add up right, maby he wasnt testing the voltage right at the cell tabs or something -easy to miss a few tenths of a volt at these amps i spose.
CamLight
10 kW
Yea, something doesn't seem right on those graphs. Perhaps it wasn't a true Kelvin connection at the tabs so the voltage drop was larger?
My test results of the 15Ah cell shows an internal resistance of 0.94mOhm to 1.11mOhm for a range of 250A to 690A, at room temperature. The voltage-under-load for the current levels were as follows:
250A = 2.85V
430A = 2.65V
690A = 2.40V
And I'm pretty sure the 15Ah has an equal or higher internal resistance than the 20Ah cell. I'd expect the voltage under load for the 20A cell at 140A (in Rod's test) to be a lot higher than he measured.
My test results of the 15Ah cell shows an internal resistance of 0.94mOhm to 1.11mOhm for a range of 250A to 690A, at room temperature. The voltage-under-load for the current levels were as follows:
250A = 2.85V
430A = 2.65V
690A = 2.40V
And I'm pretty sure the 15Ah has an equal or higher internal resistance than the 20Ah cell. I'd expect the voltage under load for the 20A cell at 140A (in Rod's test) to be a lot higher than he measured.
cell_man
100 kW
Looking back at my own test results which are far from perfect as the cell voltage is being measured after the termination, I still see over 3V at circa 100A load. I think the results above are not taken from the tab directly but rather after the leads and junctions that are passing significant current. I think a cell voltage of around 3V at 140A would be closer to the true figure. The results below still only show a 12 or 13degC increase in temperature and the cell still has a long way to go before it hits anything like what would be considered a high temperature. At 140A there's still a long way to go before cell temperature becomes an issue but I still think some kind of heat spreader/heatsink is worthwhile when the constant/average current levels get up to maybe 8-10C.
themotorman
10 mW
- Joined
- Dec 9, 2009
- Messages
- 20
I can find 20 Ah prismatics for about $30 each but have only Chinese company, not A123's , data. Desperately need real data. If you have any please send it to me directly and also to grp. rdoctorsatgmaildotcom
something that might be useful is the little red and white stickers that a123 put on the tabs, out of the 24 cells i got (they are all 3.34v) the stickers have the internal resistance and the capacity (from factory tests) for each cell.
we dont know how they were tested or anything but they say 20.4 to 21.3ah and .8mohms to 1.3mohms for my batch, id be inclined to go along with that for now seeing as liveforphysics got .8 in his tests.
we dont know how they were tested or anything but they say 20.4 to 21.3ah and .8mohms to 1.3mohms for my batch, id be inclined to go along with that for now seeing as liveforphysics got .8 in his tests.
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