# ThunderSky Internal Resistance.



## dimitri (May 16, 2008)

Adam,

all 40 of my TS160AH cells have IR between 0.32 and 0.39 mOhm. This data was provided by manufacturer based on serial number of each cell.

You can ask your reseller to provide IR data for your cells, they have it from Thundersky.

After a year of use some of my cells have significantly increased IR compared to others, which is evident from deeper voltage sags under 3C load, especially when they are cold.

Hope this helps.


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## adamj12b (May 4, 2009)

dimitri said:


> Adam,
> 
> all 40 of my TS160AH cells have IR between 0.32 and 0.39 mOhm. This data was provided by manufacturer based on serial number of each cell.


Thanks!! I just need an idea of what it will be. I averaged your 2 values together to come up with an Internal Resistance 0f .355 mOhm.



dimitri said:


> You can ask your reseller to provide IR data for your cells, they have it from Thundersky.


I have not actually bought any cells yet. Im just working out some figures to see if I will be putting the 100Ah cells in danger.

Thanks!!

-Adam


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## dimitri (May 16, 2008)

adamj12b said:


> I have not actually bought any cells yet. Im just working out some figures to see if I will be putting the 100Ah cells in danger.


Just curious, how do you use IR to determine if you are putting cells in danger?

It all comes down to discharge current, if you run at 3C or higher a lot of times then you are putting them in danger.

Obviously I realize that IR is part of equation which determines the current levels, but I think properties of your load and controller are probably more important to determine max load than cell's IR.


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## adamj12b (May 4, 2009)

dimitri said:


> Just curious, how do you use IR to determine if you are putting cells in danger?
> 
> It all comes down to discharge current, if you run at 3C or higher a lot of times then you are putting them in danger.
> 
> Obviously I realize that IR is part of equation which determines the current levels, but I think properties of your load and controller are probably more important to determine max load than cell's IR.


Well I didn't really need the IR for calculating if the cells are in danger.

I am working on a spread sheet for performance that the car will be limited to by limiting battery current to 300A. I wanted to caculate the voltage drop of the batteries under load to more accurately calculate RPM and HorsePower of the motor. 

-Adam


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## dimitri (May 16, 2008)

Ahh, makes sense.

If it helps, under 3C load at normal temps I observe about 2.9V-3.0V on my cells while the pack is fully charged.

I strongly recommend avoiding 3C discharge unless its only a few seconds at a time. I think TS claims of 3C continuous are a little exaggerated . Either that or I have exceptionally crappy cells.

Hope this helps.


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