Voltage sag under load - Some figures

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old4570
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Voltage sag under load - Some figures

I thought I would note some voltage sag figures ..  Used 4 batteries 

Trustfire Flame 18650

Yezl 18650

Xtar 2200

Ultrafire BRC3600  

I discharged at 1A - 500mA and 200mA to see battery voltage sag at various loads ..

Measurements were noted at 15 seconds , 30 seconds and 60 seconds ...  

@ 1A the largest amount of battery sag noted was to 3.72v , that's almost half a volt [ 0.46v of sag ] 

 

          Brand                 Starting Voltage             1A Discharge           
Trustfire 4.21 3.81v-15sec, 3.78v-30sec, 3.75v-60sec
Yezl4.2 3.93v-15sec, 3.9v-30sec, 3.89v-60sec 
BRC 36004.18 3.73v-15sec, 3.72v-30sec, 3.72v-60sec 
Xtar4.19 3.9v-15sec, 3.9v-30sec, 3.87v-60sec 

 

          Brand                 Starting Voltage             500mA Discharge           
Trustfire 4.19 3.99v-15sec, 3.99v-30sec, 3.96v-60sec
Yezl4.19 4.05v-15sec, 4.02v-30sec, 4.02v-60sec 
BRC 36004.19 3.87v-15sec, 3.87v-30sec, 3.87v-60sec 
Xtar4.2 4.08v-15sec, 4.08v-30sec, 4.06v-60sec   

 

 

          Brand                 Starting Voltage             200mA Discharge           
Trustfire 4.19 4.11v-15sec, 4.11v-30sec, 4.11v-60sec
Yezl4.2 4.16v-15sec, 4.15v-30sec, 4.14v-60sec 
BRC 36004.19 4.11v-15sec, 4.11v-30sec, 4.11v-60sec 
Xtar4.19 4.14v-15sec, 4.14v-30sec, 4.14v-60sec 

 

 

 Updated = Going the other way ...  

 Time to charge the batteries ...

Ive gone with the BRC3600 [ since this is time consuming ] 

 

 

1A charge rate :

Batt resting Voltage = 3.62v  [ after 1A discharge to 3v ] 

Put on the charger , and after the charger reached 1A  the voltage reading from the charger was 4.06v , if its the battery voltage , then thats a 0.44v increase . 

[ There must be some voltage overhead - higher charge voltage than batt voltage , but what is it ? = will have to test for this as time permits ] [ buy data logging MM ] 

 

 

500mA Charge 

Batt resting Voltage = 3.64v [ after 1A discharge to 3v ] 

Put on the charger , after charge current reached 500mA , the voltage reading from the charger was some 3.96/7volts  , a 0.32v increase 

 

200mA Charge 

Batt resting Voltage = 3.66v

Put on the charger , after reaching 200mA , voltage reading was 3.85v , after 60 seconds 3.83v and after 90 seconds 3.82v  [ well that was different , voltage actually dropping under charge , one possible reason comes to mind , = the battery had been rested after discharge - takes a long time to charge @ 200mA - so wanted to do most of it while I slept - so it may have initially resisted charging [ more than usual ] , but as the current flowed into the battery the resistance dissipated and the voltage dropped ] = I could be wrong !  [ so related to storing a discharged battery for several hours - Like 10 ]  

 

 

Charge VS Discharge 

1A - Discharge =  - 0.46v  , Charge =   +0.44v 

500mA - Discharge =   -0.32v , Charge =   +0.32v  

200mA - Discharge =   -0.08v , Charge =   +0.16v 

Hmmm , interesting .   

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

Edited by: old4570 on 11/01/2011 - 18:58
2100
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Thanks, that's why the regulated lights would give higher current readings for some batteries.

viffer750
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Sag depends on internal resistance of cells mostly. If the discharge current exactly 1A, and you measure the sag whitin 1-2sec, you  get the internal resistance. Sag= internal resistance.

I use 3-5 watt low value(2-5ohms) resistances for measuring internal resistance usualy. There are a couple of methods to calculate the internal resistance value, you have to use simply Kirchhoff and Ohm's law. 

 

 

 

unique engrish language... Smile

 

old4570
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Unfortunately I cheap'ed out on the Hobby charger , 1A Max Discharge ...  

ATM Im looking at spending money on a data logging Multimeter ...  Maybe the last purchase for 2011 , Ive spent plenty in the last month or so . 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

JHBUDGETLIGHT
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Thanks for providing the test results, very helpful information.  Would you happen to have 26650 batteries to compare?

-JH

Hikelite
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JHBUDGETLIGHT wrote:

Thanks for providing the test results, very helpful information.  Would you happen to have 26650 batteries to compare?

-JH

Yeah, that would be nice.

old4570
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No 26650 batteries [ in my collection ]  , though there have been some tempting lights lately for that battery . 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

old4570
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Last seen: 5 hours 10 min ago
Joined: 09/06/2010 - 02:44
Posts: 3328
Location: Land of Oz

Time to charge the batteries ...

Ive gone with the BRC3600 [ since this is time consuming ] 

 

 

1A charge rate :

Batt resting Voltage = 3.62v  [ after 1A discharge to 3v ] 

Put on the charger , and after the charger reached 1A  the voltage reading from the charger was 4.06v , if its the battery voltage , then thats a 0.44v increase . 

[ There must be some voltage overhead - higher charge voltage than batt voltage , but what is it ? = will have to test for this as time permits ] [ buy data logging MM ] 

 

 

500mA Charge 

Batt resting Voltage = 3.64v [ after 1A discharge to 3v ] 

Put on the charger , after charge current reached 500mA , the voltage reading from the charger was some 3.96/7volts  , a 0.32v increase 

 

Charge VS Discharge 

1A - Discharge = 0.46v  , Charge = 0.44v 

500mA - Discharge = 0.32v , Charge = 0.32v  

 

Hmmm , interesting .   

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….

 

old4570
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Last seen: 5 hours 10 min ago
Joined: 09/06/2010 - 02:44
Posts: 3328
Location: Land of Oz

200mA Charge 

Batt resting Voltage = 3.66v

Put on the charger , after reaching 200mA , voltage reading was 3.85v , after 60 seconds 3.83v and after 90 seconds 3.82v  [ well that was different , voltage actually dropping under charge , one possible reason comes to mind , = the battery had been rested after discharge - takes a long time to charge @ 200mA - so wanted to do most of it while I slept - so it may have initially resisted charging [ more than usual ] , but as the current flowed into the battery the resistance dissipated and the voltage dropped ] = I could be wrong !  [ so related to storing a discharged battery for several hours - Like 10 ]  

 

 

Charge VS Discharge 

 

200mA - Discharge = 0.08v , Charge = 0.16v 

 

 Always remember , the easiest thing in the world to do , is to expel hot air from your lungs and through some vocal chords ..
The resulting sound may , or may not be worth listening too ….