Optimum China Batteries

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Headway
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Post by Headway »

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Last edited by Headway on Tue, 03 Nov 2009, 10:55, edited 1 time in total.
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Post by falconEV »

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BEWARE false claims of chinese cell suppliers

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Post by antiscab »

Im guessing the top lines are rated, and the bottom actually measured?

the rising voltage under load is something ive also seen when testing TS cells, the heat causes the internal resistance to fall, which causes the loaded voltage to rise.

curious that the voltage is around 2.35v at all loads.

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Post by falconEV »

this is a test of the new headway blue cells
Their claims of 10C+ are pure B.S.
high impedance is indicated by the heat rise under load
the dotted lines are the temp rise, not voltage
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Post by woody »

Hi Falcon,
thanks for this testing.
Could you post the raw data?
Are these the 38120p cells or 38120l/s?
Up to 6C looks like a voltage drop of 0.1V / C I.E an internal equivalent series resistance of:
V=IR ; R = V/I = 0.1 / 10 = 0.01 = 10 mOhm
this would be heating the cell at P=I^2R @ 5C = 50^2 x .01 = 25W.
From the voltage 6C looks a bit better than it should, 7C looks worse like 8C should.

for the 38120S/L headway claim 10C continuous 100Amps for 6 min)
evcomponents have reduced this to 5C
Based on the graphs I'd say 5C continuous looks like nice treatment of the cell.
It would be very interesting to see 100amp graph, the voltage should be at most 2.2 volts.
the 38120P is claimed 20C continuous (200amps for 3 mins)
cheers,
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Post by woody »

The difference between the published impedance (1.8mOhm) and the equivalent series resistance (10mOhm) means:

Each cell can deliver 250W, not 440W.

I.E. I'm only going to get 50kW from a 200 cell pack, not 88kW :-(
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Post by acmotor »

Ummmm, I wonder what the manufacturer means by 10C in any case ?

I would have thought 10C for a minute. i.e. doesn't go below Vmin or burn out terminal wiring at that rate / in that time.

How significant is 10C for the full battery capacity ?
That is not what an EV would do.
How long does it take to do 0-100kmph anyway ?

Despite that, the headways seem in this data to be rather avarage.
LiPo still looks the best for continuous high rate discharge.
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Post by woody »

Hi FalconEV,

Hemonster did some testing a while ago at 75A and got 7.1 mOhm.

Have you got details of the testing?

cheers,
Woody
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Post by woody »

Richo pointed out in Hemonster's thread that 1.8mR is the BMS (fet?) resistance.

I found this
Headway 38120L Spec
which says <8mOhm.

Edit: forgot http:// in front of URL
Last edited by woody on Mon, 19 Oct 2009, 08:52, edited 1 time in total.
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Post by coulomb »

I'm getting a 404 on the .pdf file.

Edit: now fixed. Thanks.
Last edited by coulomb on Tue, 03 Nov 2009, 17:49, edited 1 time in total.
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Post by Johny »

Click on it then once the browser complains, clip the AEVA stuff off the front of the address. Woody must have posted in the "Quick Reply" editor.
Last edited by Johny on Mon, 19 Oct 2009, 08:47, edited 1 time in total.
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Post by woody »

Edited the link, http://www.evfr.net/uploads/headway/38120S.pdf for those in email land - I forgot the http://.
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Post by Johny »

This report that Ian at Zeva (as it was) compiled on the headway 38120 cells still appears to be one of the better resources on these cells. There appears to be a bit of miscommunication over whether Headway claim them to be 5C or 10C. Ian(Zeva) clearly stated that they were claimed to be 5C cells with a 10C peak.

Unfortunately the Headway spec. that woody found doesn't help too much as it states Maximum charging current twice. The second one looks like it is supposed to be maximum discharge current. Nowhere does it state the capacity at stated discharge current, however my take on all the various discussions I have read is to expect rated AH at 1C tapering down to 90% of that at 5C. USA vendors of these cells haven't helped with confusing details that changed a few weeks ago.

Edit: Not to ignore hemonster's Headway cell testing which I also regard as an excellent reference.
Also added missing URL.
Last edited by Johny on Mon, 19 Oct 2009, 09:10, edited 1 time in total.
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Post by falconEV »

Testing is done using a CBA II Pro and two amplifiers
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Post by woody »

Hemonster wrote: Though I've written to EVPST to send me 2 samples of each 10AHr adn 12AHr cells. I plan to test these using a labjack setup such as Ian did on Zeva.
Hi Hemonster,

I found this old post and was wondering did EVPST get around to sending you some samples eventually?

cheers,
Woody
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Post by Headway »

Yes, Headway have new product now --38140S cell(3.2V12AH),its height is 142±1(mm),its Diameter is the same as 38120(38±1mm), so 38120 assemble block can be used on 38140S cells. its weight is about 400g.

please contact me,if you want.

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Post by falconEV »

I don't want
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Post by Richo »

Not unusual for another battery seller to put down other batteries.
falconEV wrote:BEWARE false claims of .. cell suppliers


Good advice Image
So the short answer is NO but the long answer is YES.
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Post by Johny »

Sorry to ask the dreaded $$$ question but how does the 38140S compare in price to the 38120S?
Also, can packs be made up in the Al-alloy boxes with the 38140S cells?
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Post by woody »

Headway wrote: Yes, Headway have new product now --38140S cell(3.2V12AH),its height is 142±1(mm),its Diameter is the same as 38120(38±1mm), so 38120 assemble block can be used on 38140S cells. its weight is about 400g.

please contact me,if you want.

Image
Hi Lorraine,

is the internal resistance lower for the 38140S?

What is the price difference?

cheers,
Woody
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Post by woody »

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New Specs for headway cells.

From DIY Electric Car Forums

Internal resistance lowered all round.

Larger range of cells from 8Ah to 16Ah.

I believe the price/Ah is consistent except the 38120P has the 25% premium - i.e. 38120P 8Ah costs the same as 38120S 10Ah.

cheers,
Woody

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