[GizmoEV]

Even with all the data I've seen, including JR's graphs, there is nothing saying that there is a difference in the charge profiles between the different LiFePO4 prismatic cells. Just because one manufacturer says 3.65-4.00V and another says 3.6V doesn't make them different. The discharge tests JR posted doesn't either. It merely shows that the internal resistance of one cell is different than another. That difference could entirely be because of the thickness of the coating on the plates. It is entirely possible that CALB is being more conservative than TS, et al.

[tomofreno]

Originally Posted by JRP3

Probably the easiest thing to do is compare curves of TS and CALB at the same C rate. Jack has done the work for us. You can see the differences the TS 160 voltage climbs much higher while still adding significant capacity, the TS 200 less so, and the CALB 180 even less.

http://1.bp.blogspot.com/_i_c2BM_uBw...argecurve2.jpg

During discharge the CALB's don't sag as much and have a flatter curve.

http://1.bp.blogspot.com/_i_c2BM_uBw...hargecurve.jpg

To me those are fairly obvious differences in behavior.

Those curves look a bit strange to me - smooth toward low V end, jerky toward high V end.

Keep in mind you are comparing two "populations" of cells, TS and CALB, based on a sample size of 1. Charging curves from 16 of my 180Ah CALB (2009 SkyEnergy) cells are below. The spread in cell voltages over most of the charging time is around 0.03V, but would be quite a bit larger if charging at 1 C as Jack did rather than at the 0.11C used here. Maybe on the order of the spread shown between TS and CALB on Jack's graph, if the spread scales linearly with charging current.
Cell V while charging.pdf

[JRP3]

Yes it is a small sample group, but the results are similar to curves published by the cell manufacturers. I suppose we'd need to test a few of the newest cells from each company, but the recent CALB CA cells appear to be even stiffer than the SE cells, so CALB may still do better than the others.

[JRP3]

As if on cue

Well it looks like jack finally put the screws to some 40ah cells. The results are definitely encouraging. Roughly half the sag at 2x the load compared to the old SE cells.

http://www.diyelectriccar.com/forums...tml#post319149

[EVfun]

Can you spare me the time of watching one of Jack's videos and just tell just where to look or what the results where?

I followed that test on the CALB CA 180 amp hour cell and it is impressive. It looks like around 0.3 milliohms of internal resistance. That is an incremental improvement that may be worth paying for. For comparison, my TS 60 amp hour cells are 1/3 the capacity and I would love the internal resistance to be 0.9 milliohms. The measured internal resistance is 1.4 milliohms. That is good for 6C, but not for 10C.

For Drgrieve, here is a video from a Jay Whitacre, a professor who really knows a bit about what goes on inside a LiFePO4 cell. A number of us here can share our experience with them, Jack and tell you about his too, but none of us are scientists or professors on the subject.

[Ziggythewiz]

Originally Posted by EVfun

That is an incremental improvement that may be worth paying for.

Paying what? The new cells are the same price as the old.

[EVfun]

"Paying for" in terms of consider replacement of perfectly working existing cells for more power. Still, by reports I've heard the CA cells are a little more than $1.21 per amp hour, which has been a common price for the SE cells.

[Ziggythewiz]

Oh sure, I wouldn't replace a working pack for the upgrade unless the old is getting used in the wife/daughter's e-mobile, but your price isn't far off. Most people seem to be getting the greys through Jack, and should know they're paying a decent markup but seem happy to do so.

[JRP3]

Originally Posted by EVfun

Can you spare me the time of watching one of Jack's videos and just tell just where to look or what the results where?

Nope, you have to suffer through it Actually I haven't yet seen it myself, just read it in the link I posted. Jack will reference it in his blog and post charts I'm sure eventually.

[tomofreno]

Originally Posted by JRP3

As if on cue



http://www.diyelectriccar.com/forums...tml#post319149

Yes, the CALBs seem to have a lower internal resistance compared to TS cells, but I thought you were saying they ran at different voltages compared to TS - something like the difference between lithium cobalt and LFP, but less. I think Gizmo and I are saying the TS and CALB are the same chemistry, LiFePO4, so operate at similar voltage levels, but yes there are some differences, such as internal resistance. There are also differences in internal resistance between different capacity CALB cells.

The battery stuff I've read recently makes me think that there aren't going to be any significant changes for quite a while, so performance and cost will likely float around about where they are now, with tweaks like lower internal resistance of the CALB gray cells. I don't much care about higher specific power, I want higher specific energy and lower cost.