# Manual LifePo4 top balance/equalizing, resting voltage



## Duncan (Dec 8, 2008)

Hi Steven

These are Headways??

I have 12 16Ah cells I bought as samples and I am doing some charge discharge cycles - be a few weeks before I have good data

Can you attach your spreadsheet somehow??


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## steven4601 (Nov 11, 2010)

Hi,

Yes. HW38140 12Ah. 
And

Not at this stage. Data is incomplete. Also, what would my data be of use for your pack assembly?


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## Duncan (Dec 8, 2008)

*Also, what would my data be of use for your pack assembly?

*I am trying to get my head around exactly how these cells will operate within my pack*, *from my initial charge discharge cycles its not as simple as I hoped, the more data the better,
I will be publishing my data on this site - when its complete!

also one of the 12 samples has died - I don't think I killed it - how are yours doing?


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## steven4601 (Nov 11, 2010)

Oh dear What did you do to it ? 

No killed cells on my end so far. But I have not used them up to their specs yet.I stressed a few only to 3C with my bench equipment. 

So far I have measured just over 200 cells before top balancing now, all somewhat in the same voltage of 3.315 to 3.335 (resting voltage) and their expected SOC is 90% or higher. (reason i know this is that on avarage only 390mAh is being added to each cells during top balancing. ~21000mAh added for 54 cells in parallel) 

I'm considering installing balancing plugs on the cell packs just in case I need to rebalancing while they are in the vehicle. Also voltage monitoring during 10C load would give insight in how well the cells are matched together. 

Are you considering a VoltageMS/BMS ?


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## jackbauer (Jan 12, 2008)

I have noticed this behavour with my headway pack. And i haven't done any balancing. I have a 48s4p pack of 16ah cells. I charge to 165v. At cuttoff , most cells are 3.4 something volts. A few hit 3.6v. If i measure voltage a few hours later they will be in the ranges you found.


I have four cells on the bench in a discharged state as i'm doing a small scale bottom balance experiment before doing the traction pack. I do find the headways to be much more "springy" in voltage terms than prismatics. I believe there to be very little energy storage in a headway much above 3.4v.


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## Yabert (Feb 7, 2010)

steven4601 said:


> Some strange results with my top-balancing has happened. Most cells are at either 3.350mV or 3450mV.


I saw the same difference in voltage with my headway 10Ah!

After a fresh charge at 3.6v, the resting voltage after 24h of my HW buy in April 2010 is 3.34v and the resting voltage of my HW buy in November 2010 is 3.43v.

Chemical differences??


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