# Headway Internal Resistance



## DavidDymaxion (Dec 1, 2008)

*Endless sphere had a thread where some of their members measured much higher than spec internal resistance on Headway **38120P batteries. This was back in 2008. It looks like Cro has had good results. Has anyone done a recent internal resistance test? Has the anything changed from 2008? Thanks.

*


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## LithiumaniacsEVRacing (Oct 9, 2010)

I will be testing my Headway shipment soon. I will video all results, and post results. I will put a few to the torture test!  Boom!



DavidDymaxion said:


> *Endless sphere had a thread where some of their members measured much higher than spec internal resistance on Headway **38120P batteries. This was back in 2008. It looks like Cro has had good results. Has anyone done a recent internal resistance test? Has the anything changed from 2008? Thanks.*


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## crashnfool (Sep 26, 2009)

Good Idea we should all post up our numbers and see what we get as an average...


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## DavidDymaxion (Dec 1, 2008)

Thanks in advance for posting your numbers LEVR and CNF.

I just ordered a small number to test, I'll post up my results. I also ordered some new China High Power 10 Ahr cells to compare.

I trust you mad scientists are wearing goggles during the test! Also cover the batteries. I have liberated some electrolyte -- be careful.


crashnfool said:


> Good Idea we should all post up our numbers and see what we get as an average...


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## Yabert (Feb 7, 2010)

DavidDymaxion said:


> *Endless sphere had a thread where some of their members measured much higher than spec internal resistance on Headway **38120P batteries. This was back in 2008. It looks like Cro has had good results. Has anyone done a recent internal resistance test? Has the anything changed from 2008? Thanks.*


.....the cells and all are between 3 and 3.5 mΩ

http://www.diyelectriccar.com/forums/showthread.php/smart-fortwo-ev-high-power-version-51472p3.html


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## DavidDymaxion (Dec 1, 2008)

Yabert, many thanks for posting that. I had searched on Headway, tons of results, but apparently gave up too soon. < 3.5 mOhm is really good. Did you measure how hot they would get under test?

From the link below, Jack Bauer had quite the explosions via massive overcharging. The 10 Ahr China High Power cells I tested just let out some steam and a small puddle of electrolyte.


Yabert said:


> .....the cells and all are between 3 and 3.5 mΩ
> 
> http://www.diyelectriccar.com/forums/showthread.php/smart-fortwo-ev-high-power-version-51472p3.html


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## ElectriCar (Jun 15, 2008)

Yabert said:


> .....the cells and all are between 3 and 3.5 mΩ
> 
> http://www.diyelectriccar.com/forums/showthread.php/smart-fortwo-ev-high-power-version-51472p3.html


Did you mean less than .3 and .35? I thought these small cells had much lower resistance than prismatic cells, which are running .4 and up. If you draw much current through cells with those numbers you're in the lead acid realm of resistance and you know if you've ran lead what that's like. *I lose a full 20% of my pack voltage at 250amps on lead! *


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## DavidDymaxion (Dec 1, 2008)

Don't forget you'd parallel 25 of these to have the same Ahr as a 200 Ahr prismatic cell. That means the internal resistance would now be 3.5 mOhm / 25 = 0.14 milliOhms, about 10 to 20 times as good as a typical 200 Ahr cell.


ElectriCar said:


> Did you mean less than .3 and .35? I thought these small cells had much lower resistance than prismatic cells, which are running .4 and up. If you draw much current through cells with those numbers you're in the lead acid realm of resistance and you know if you've ran lead what that's like. *I lose a full 20% of my pack voltage at 250amps on lead! *


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## Yabert (Feb 7, 2010)

DavidDymaxion said:


> < 3.5 mOhm is really good. Did you measure how hot they would get under test?


I performed the test at room temperature (22 c).

I also test a first batch of cells I had buy for my motorcycle project in april 2010 and all cells was between 2.9 and 4.5 mOhm..... Only 6 or 7 cells had over 4 mOhm on 94 cells.

Don't forget the test is performed with 38120S 10Ah cells.
But for me 10Ah at 15C (150A) or 8Ah at 20C (160A) is realy close...


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