Author Topic: someone LIPOs expert there???  (Read 747 times)

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Offline dramoto

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someone LIPOs expert there???
« on: July 23, 2016, 02:21:01 am »
Hi...
Just trying to look at the doors of the knowledge of batteries. I began to use "logview studio" to check what is happend during the charge of my RC lipo´s. And I notice that the voltage current make a strange change in the curve from 4.05V to 4.1V cell voltage, during the constant current charging fase. Looking the curve it´s like inside the cell they are two batteries in serie (like two different chemistry), and from 3.70V to 4.10v is charging the first one, and at 4.10 begin the another one.
Someone can explain for a dummy what is the reason for this? if they are one...
It´s normal on all Lipo´s or maybe only in the brand that I have?

Thanks

From the attached graph, it´s the charge of a 3S Lipo. The upper blue line is the total battery voltage. Red line is the current. Next green line is the capacity.
And at the bottom, three lines together of the voltage of each individual cell. 

[Edit] Interesting too the peak in the voltage at 3.85V. Like it´s a point with more activity. I see interesting beacouse 3.85 it´s the recomended value for "storage" a LIPO.

 
« Last Edit: July 23, 2016, 02:27:44 am by dramoto »
 

Offline Kilrah

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Re: someone LIPOs expert there???
« Reply #1 on: July 23, 2016, 02:45:12 am »
Not sure what you mean. The last graph clearly shows your 3 cells are well matched.

 

Offline dramoto

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Re: someone LIPOs expert there???
« Reply #2 on: July 23, 2016, 03:07:25 am »
Sorry for my poor capacity of explain me in English.

The information of the curve is great.
I´m speaking about the "non-lineality" of the cell voltaje between the chart points 16:45 to 16:55. The "hump" that the cell voltage does from 4.05V to 4.10V.
I suppose that it has a chemistry reason. I didn´t see until now jump´s or hump´s in the charging curves of NIMH or NICD

About the little peak that is in the blue line at the chart point 16:20. I find it curious that it coincide with the recommended "voltage storage".
« Last Edit: July 23, 2016, 03:08:57 am by dramoto »
 

Offline Kilrah

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Re: someone LIPOs expert there???
« Reply #3 on: July 23, 2016, 05:07:11 am »
Could be temperature, could be the quality of the contact in the charging wires, could be chemistry...

The jump at 16:20 is very typical of a change in contact resistance in the charging cable, e.g. by just moving the battery or cables/plugs given that the cell voltage doesn't have the same jump.
 


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