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

[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.

[ZapPat]

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,

I picked up five zippy flightmax 15C packs when you pointed out the special a couple weeks ago, and I am very impressed by them so far.

Here's a picture of one pack (5 cells, 18.5V nominal, 5Ah), and it measures 145mm X 40mm X 50mm:

Zippy LiPo 15C flighmax 5Ah, 5 cell 18.5V nominal.jpg (73.55 KiB) Viewed 2046 times

Since a lifebatt/PSI/BMI is about 140mm long X 38mm dia, this would mean that a LiPo pack made with these would be almost 2.5X more energy dense than a same sized PSI/etc pack!

GO Doc, Go!!! You really should consider changing your name to DocBatt after this, since your excellent comparison charts are certainly going to be used by many internet surfers everywhere to make enlightened battery choices.

[TylerDurden]

I picked up five zippy flightmax 15C packs when you pointed out the special a couple weeks ago, and I am very impressed by them so far.

Blue flames... truth in packaging.

[liveforphysics]

I'm glad you are enjoying those batteries Once you go LiPo, it's very tough to want to lug around anything else, and put up with wimpy discharge rates, battery heating, saggy voltage etc. Of course if your application requires a saftey chemistry, then you gotta pick from the saftey chemistry batteries.

And Fantastic work Doc! You are a major asset to not only this forum, but to people all around the world who have an interest in making battery powered devices. PM me your address.

Best Wishes,
-Luke

[ZapPat]

I picked up five zippy flightmax 15C packs when you pointed out the special a couple weeks ago, and I am very impressed by them so far.

Blue flames... truth in packaging.

That's a pheonix, though, TD, so it'll just fly right back out of those nice blue flames to live again and again...

I actually ran three series packs to the ground the other day (until the power level dropped almost all of a sudden to almost nothing), without a BMS or any cell-level LVC. I then thought about all the over-discharged Lipo stories, where they catch fire while charging afterwards. So I charged them up anyways of course, and low and behold they sucked in all their Amp-hours without a problem, and still work great. Here's a site with very good battery info; read the end of the linked page, under "Lithium Charged but Not Guilty?". It's good to be vigilant and fully aware of possible dangers as with anything, but remember that fear is a mind-killer.

Anyways, anyone wanting to read/post about modern LiPos can check this thread here, and keep Doc's batt test thread here relatively clean (hit me Doc): LiPoly evolves while LiFePO4 is stagnant?

[Doctorbass]

like i said to Phil, this morning it was 4:20am when i was still playing with some A123 for preparing for test compare

I took some of those...(please note they come from "deffective pack" that had few cell low)

and i did a discharge to test the RI with 10 in parallel... and:

I measured....

1 miliohm.. lol .. exactly the corresponding 10 miliohm per cell but with 10 in parallel..

I'll measure every single cell of these 10 cells (picked from 2 or 3 dewalt pack) and will choose the 5 bests.

then i'll parallel them and measure them.

The pack with 5 parallel cells i showed was made owth the deffective low cells took appart from the deffective pack.

I always keep these cells eventhou they have 1700 or 1900mAh.. The last time i measured it it had 8750mAh out of 5parallel low cells.

I plan to test it too and will compare low cells with good cells.. that will give us a real comparaison with bad and good cells

In fact i would almost call them bad cause they had less than 1V each when i took them appart.

I plan that i'll need 4 days to measure them.

results soon!

Thanks for yuor encouragement guys!.. (is that the good word?..) I often use Babelfish translatoe..

Doc

[Doctorbass]

GO Doc, Go!!! You really should consider changing your name to DocBatt after this, since your excellent comparison charts are certainly going to be used by many internet surfers everywhere to make enlightened battery choices.

Yeah.. that might be an idea since on google there is only 5 or 6 entry on that name...

But i dont know... it's been for long time i was called Doctorbass and that i adopted that name..

When i was almost playing with subwoofer and car audio amplifier few years ago, some friends called me that name and that continued for me.. that began on Dbdragracing website.. years 2000 or 1999 if i remember correctly..

I agree that ending doc with "bass" does less sens than batt..

but you guys what do you think..? does it really matter rebaptizing me?

... replacing 2 S with 2 T





Doc

[dnmun]

stick with drbass, can you measure the internal resistance on the individual bad a123 cells with your mega charger thingy, before charging them up? and then later of course.

[Doctorbass]

stick with drbass, can you measure the internal resistance on the individual bad a123 cells with your mega charger thingy, before charging them up? and then later of course.

i'll put that on the Biiiiiiig to do list

Doc

[oatnet]

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

That has been my experience, but I thought a read somewhere that LifeBatt was peak-charged 3.35v, must have been wrong. Since it is 3.65v, I am really suprised that the Lifebatt in Bob's graph discharged 20a at @ .1v lower than the Headway. Granted this is an original green cell, but still... Of course, the current PSI=LifeBatt that Doc tested discharges at higher voltage than the Headway, I guess that is the relevant comparison.

-JD