Yesa vs Headway vs PSI vs Ebike.ca 12Ah LFP test graph

[Doctorbass]

i'm not disputing anything pat, i just wondered if it was possible to calculate the IR for me at extremes of temperature. since he has 3 different chemical formulations at the same age, and history, compared on the same equipment. maybe to establish a baseline for later lifepo4 formulations.

in his original headway thread, i was able to see that IR almost tripled from initial discharge to close to terminal discharge using RLT's graphs. and i could do that too from these graphs like i did last year, but doc wants to use the IR test he established and i thought that was ok since he has good experimental technique and i think the numbers will stick for a long time.

just curious about how lifepo4 works, and why one formulation or cell type maybe is better in different situations.

and i am also curious about the charge cycle, what is the equivalent to internal resistance then? i always think about the review i read where they were talking about the theory of the supersaturating phenomena where the lithium is precipitating out of the electrolyte separated from the anode, not touching it, that has always interested me. what other electrolytes could be used sorta thing.

anyway, that's why i asked, now i included a request for IR over the discharge cycle so it doesn't make it easier for him, plus the high current runs he wants to do.

Dnmun, this is faisable but that would take alot of time!!! .. test over cycles are ... well... hmmm... are... VERY LONG TO ACHEIVE !!!

the best would be to test them with normal ebike use and to know the mean current of use... that could happen for me when snow outdoor will have dissapear!

Doc

[dnmun]

ok,using my graphical interpretation on doc's CBA graphs to evaluate internal resistance. in milliohm.


manufacturer---1.11Ah--5Ah--8.85Ah
PSI-----------------6.8-----7.9----16.5
YESA---------------7.6-----8.2----15.6
Headway---------11.2----11.5----15.6
LifeBatt----------23.2----23.2----25.3 (added by edit using the lifebatt graph at 20A from bob's old lifebatt thread)
first 3 done at 22C by doc. if anyone gets some other numbers at different temperatures, try to keep track of where in the discharge it is so we can interpolate, thanks, dm

[oatnet]

LifeBatt----------23.2----23.2----25.3 (added by edit using the lifebatt graph at 20A from bob's old lifebatt thread)
first 3 done at 22C by doc. if anyone gets some other numbers at different temperatures, try to keep track of where in the discharge it is so we can interpolate, thanks, dm

I had forgotten about that LifeBatt graph. I really want to see Lifebatt/BMI on the same graph in comparison, but maybe this will do for the moment. Here is my crude 20aCBA headway test, compared to Bob's 20a graph using similar hardware:

38120 HH23 11572 20a-2c_shrunk.JPG

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lifebat%20curve.jpg

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I was babying the new cell and terminated at only 26v which makes the curves harder to compare, and the lifebatt has a lower nominal voltage, but...

The headway discharged 20a at 3.0v, at 6ah it has dropped .09v, and then trails off .4v to 2.6, where it has supplied 9.19ah.
The lifebatt- discharged 20a at 2.9v, at 6ah it has dropped .08v, and by the time it trails off an equivalent .4v it has supplied @9.75ah.

So based on these crude tests, I theorize that the lifebatt delivers a slightly flatter curve and slightly more ah, but at lower voltage meaning it probably delivers about the same wh as the headway. I know the lifebatt starts at a lower voltage, but if I remember correctly the headway was about 340g, I googled posts describing the lifebatt as 360g, so by weight/volume the headway is delivering slightly better voltage and probably equivalent wh. granted, this is only 2c, I wonder how the voltages compare at 5c.

So please bear with me as I reason out the pros and cons, as I see them, for MY application, a large-vehicle EV Conversion.

The Headway is rated at 5c continous, and the LifeBatt is double that for 10c. For my Bus, I really need at least 80ah/cell simply to have enough KW for a meaningful distance. 80ah at 5c that delivers 400a, more than enough to supply my 500a controller, so I don't really need to pay a premium to get 10c. For vehicles like ebikes and electric motorcycles that can only carry smaller ah packs, but still need high discharge rates, the lifebatt sounds like a good fit - if the packaging is compact enough.

The cycle life of the pack is another issue. A 120v80ah pack yields 9.6kw/cycle, at 350whpm that will deliver 27.43 miles, more than enough for my daily travels. Headway estimates 1400+cycles, so even if I used a full cycle every day, it should be good for 4 years/38,400 miles. LifeBatt claims 3000 cycles so it could be good for 8.5 years of daily full cycles, which is far superior, but for MY application I'm happy to save the money now and replace them with whatever hot new technology is around in 4 years.

Which gets us to cost. One can buy a 320 cells from Victoria to build a 120v80ah pack, shipped air to your door, for $4,960. For comparison to Lifbatt's products, a 144v80ah pack would be $5,952. Lifebatt's 144v10ah pack lists at $3,000, you would need eight of them to build an equivalent 80ah pack, or $24,000 before any 'volume' discounts. ( http://www.lifebatt.com/retail_sheet.asp - 14410-HPS 144V / 10Ah w/VMS, 2 Terminals 24.5 546 182 207 53.9 21.50 7.17 8.15 48 $3,000.00 )

So the way I look at it, LifeBatt's have twice the cycle life, have twice the c-rating, and include nice packaging/monitoring/charging. Headway's provide slightly higher voltage per cell, weigh slightly less, and cost 1/4 as much as LifeBatt, but you need to package them yourself - a learning experience I happen to enjoy and prefer

-JD

[olaf-lampe]

Hi Doc,
why don't you give peakbattery.com a chance? They have very nice 26650 cells and a quite competitive 90AH cell as well. (300/700A)

I'm not related to them, just a satisfied customer
Olaf

[TylerDurden]

JD,

Thanx for posting your cell comparison and pricing info... it looks like more large EVs can get lithium this year (without paying through the nose).

[Doctorbass]

Hi Doc,
why don't you give peakbattery.com a chance? They have very nice 26650 cells and a quite competitive 90AH cell as well. (300/700A)

I'm not related to them, just a satisfied customer
Olaf

I should receive 5x K2 cells to test next week that's for an electric 911 porsche battery pack... 2500 of these cells! I have the job to make the battery pack ... using brand spot welder!

150kW Motor ordered!

http://porschestrom.blogspot.com/2008/11/project-start.html

i'll post graph.. dont worry!

Doc

[dnmun]

you ordered a motor from unique mobility? that is really a nice car. why couldn't they scrap a honda CRX. the ones from 84-87 would weigh under 1400lbs without the motor, there is space up front for some batteries along with the motor, and in the rear too. plus they are easy to find with the head gasket blown because the head gasket seems to blow after 15-20 years, so you can get them cheap for $200-300. then you could use 70kW motor and still get to 55-60mph easily. i doubt if the porsche 911 is gonna have space for the batteries since it is already so compactly designed. i have seen several CRX conversions, and i have 3 or 4 of them myself, just don't have the heart to convert one since they are already so efficient.

[Doctorbass]

you ordered a motor from unique mobility? that is really a nice car. why couldn't they scrap a honda CRX. the ones from 84-87 would weigh under 1400lbs without the motor, there is space up front for some batteries along with the motor, and in the rear too. plus they are easy to find with the head gasket blown because the head gasket seems to blow after 15-20 years, so you can get them cheap for $200-300. then you could use 70kW motor and still get to 55-60mph easily. i doubt if the porsche 911 is gonna have space for the batteries since it is already so compactly designed. i have seen several CRX conversions, and i have 3 or 4 of them myself, just don't have the heart to convert one since they are already so efficient.

The porshe project is not MY project.. I am associated with the guys that work on it and my job is the battery and all surrounding stuff.

They did not choose a CRX like Metric mind did or any others.. simply because the car that have acces is a porshe.
The battery pack will be spit into 5 modules to get the same handling vs weight placement than a normal porshe.
Now let's return to the original thread

Doc

[Doctorbass]

UPDATE.. 6feb 2009.. Ypedal green 12Ah LFP from ebikes.ca tested!

Please note that thisone is a 12Ah and not 10Ah like the rest of the tests.

Compared to the other cells the curve look more regular from one discharge to another..

But it did not the 12Ah rated... eventhou at 1A

I tested it at 1, 5, 10, 20, 30 and 35A.. just like the other cells.. not in C rate.. like 1C 2C..etc otherwise i would need to discharge 1C at 12A and that just can not be conpared to the rest of cells...

Please note that the last 35A curve stopped before reaching the 2.0V limit.. that is due to the temp limit of the CBA so i tried to extrapolate and continu the curve by drawing the rest of it.. you can see if you zoom on it..

The voltage measured directly on the cell screw correspond in the +/-1mV percision compared to the graph wich is still good and confirm that every connections between the cell and the CBA are still ok.. (cheched the calibration it few days ago and it was also still perfect)

Now here is the graph for you Ypedal.. and others

Doc

[Ypedal]

Sweeeet !!

I need to whip out my ruler and calculate the volume of the 12ah cell vs PSI vs duct tape cell .. what an exciting friday night !!

Damit.. i totally forgot to include a foil 12ah LFP cell from the early Cheer Ocean days.. prior to Ping ! ( only other person who i know that has used these cells is Oatnet. )

[oatnet]

UPDATE.. 6feb 2009.. Ypedal green 12Ah LFP from ebikes.ca tested!

Thanks again for taking the time to do this testing Doc - I know these cells really well, they powered a whole series of prototypes for me, so your tests give me an excellent baseline to compare other cells to. Sometime I would love to see the 35ah curves for your recent tests (yesa, headway, PSI, and ebikes.ca) overlaid, ah and wh - but is Friday night, you have worked hard, I hope you are out having fun.

Damit.. i totally forgot to include a foil 12ah LFP cell from the early Cheer Ocean days.. prior to Ping ! ( only other person who i know that has used these cells is Oatnet. )

<grin> Oy, Cheer Ocean and the Flintstone Chargers (sounds like a cheap cover band) from the fleet of first generation of LiFePO4 packs I tested in summer of '07. This is the only one of those cheap packs I kept - I had overdischarged cell#11 on both 36v packs when bank#11 on a flintstone charger died , didn't seem right to pass them on like that. I later replaced the dead cells with two spare falconEV cells (like the ones doc just tested), and right now they are on the Prototype I am using to mess around with gear motors. That generation was the first and worst, but it definitely has lasted long beyond the three months an early naysayer was touting

I have a Cheer Ocean full-pack discharge curve from the dark ages, at a piddly 2.37amps:
viewtopic.php?f=14&t=2089&p=27604

BTW Gaston, thank you too, for sending the cell to Doc for testing!
-JD

[Doctorbass]

A little sumarry of all these 4 measureds cells.

(Important NOTE: all EXCEL data and CBA II files are still availlable to people that ask me for them )

[Doctorbass]

UPDATE.. 6feb 2009.. Ypedal green 12Ah LFP from ebikes.ca tested!

Thanks again for taking the time to do this testing Doc - I know these cells really well, they powered a whole series of prototypes for me, so your tests give me an excellent baseline to compare other cells to. Sometime I would love to see the 35ah curves for your recent tests (yesa, headway, PSI, and ebikes.ca) overlaid, ah and wh - but is Friday night, you have worked hard, I hope you are out having fun.

-JD[/quote]

Friday night.. lol.. I play with these cell measurement. this is not depleasant job for me!

here are your graph JD

[AndyH]

I have $10US that says the BMI cell won't perform significantly better than the PSI cell...

[Doctorbass]

Have you ever saw a Cells meeting?

[slayer]

hey doc how about a 5p a123 test.?
i would like to see that

[Doctorbass]

lol!!! Do you mean this A123 group?




you just read my mind man!

Comming soon!! watta nice idea !!!


Doc

[oatnet]

lol!!! Do you mean this A123 group? you just read my mind man! Comming soon!! watta nice idea !!!
Doc

Oh YEAH! Doc, this thread just keeps getting better and better.

Friday night.. lol.. I play with these cell measurement. this is not depleasant job for me!

Friday night... And we're sitting here reading it - not an unpleasant job for us either! Fascinating how the 10ah/5c Headway and 12ah/3c Green cells line up on much of both curves, similar powder? I wonder why the Headway's voltage drops off early and then aligns with the Green cell again.

I have $10US that says the BMI cell won't perform significantly better than the PSI cell...

Sucker Bet!

Ya know, I lost track of the fact that PSI=BMI, that discharge curve is higher than I would expect, having seen that early LifeBatt cell curve Bob published. I was thinking LifeBatt were 3.3v, am I confused, or are the later cells charged to 3.65v?

-JD

[GGoodrum]

Pretty much all LiFePO4 cells have a "nominal" voltage of around 3.3V, and all optimally get charged to 3.65V.

[liveforphysics]

I'm going to send you regular cheap zippy 5Ah LiPo cells soldered together to be a single 10Ah cell.

We can see if you can find any measureable voltage drop with just a 35amp load

Then you can calculate energy and energy density so people can see what the lure of the "darkside" battery chemistry is all about,

[olaf-lampe]

I'm going to send you regular cheap zippy 5Ah LiPo cells soldered together to be a single 10Ah cell.

We can see if you can find any measureable voltage drop with just a 35amp load

Then you can calculate energy and energy density so people can see what the lure of the "darkside" battery chemistry is all about,

yes, and after the discharge orgy, we overcharge all of them about 10% and then make a judgement

just kidding
Olaf

[liveforphysics]

Ok, but we do the overcharging at your house, not mine

[Deepkimchi]

I'm running the Lifebatt 10 ah pack & FalconEV Green 12 ah packs in series without an LVC. I'm glad in the past I picked 8ah as a "be home" point.

Namely if I went joy riding, wouldn't go past 4 ah use then I'd turn it back home.

The graphs seem to show my choice was a good idea. Not starting any long stories why I'm running w/o LVC.

DK

[Deepkimchi]

Since a 29V cutoff on a 36V pack gives 2.4V (when you have to start pedalling), I wonder which is better?

Seems like PSI and Yesa give more uumph V for a shorter time before pedalling.

Headway and the 12ah pack are lower immediately, but a longer time before the pedal point.

DK

[Toorbough ULL-Zeveigh]

man, that LFP discharge is billiard table flat
whats especially impressive that it holds steady even at the highest rates.
which means it can deliver even higher amps where the other would probably start to tank.

Doc, which characteristic do u place more importance on, higher voltage maintenance or flat discharge?
i'm thinking the latter is preferable since u can compensate for the voltage sag by adding only a few more cells.
this may be why Justin chose to sell these out of all the different ferro-phosphate flavours he tested.
a123 should be equally flat, but with 5 in parallel with little drop in V i expect, interested in seeing how much exactly.
great work as always.