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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 12-15-2012, 10:21 PM   #1
mclarkson
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Default Revolextrix Cellpro Multi4 - what's it doing?

I have a Revolextrix Cellpro Multi4. The charger works great and Iím very happy with it, but Öhereís what I donít understand:

I put on a 3S LiPo and start charging on setting #1 Ė Lipo Generic Accurate Charge. (The only setting I use.)

Now, as the battery crosses past 12.6v the charger beeps at me. 12.6v (4.2V/cell) is the nominal full voltage of a 3S Lipo.

The individual cells show something like 4.206 v/cell.

The charger fuel gauge, though, shows 93-94%. And the charger keeps going.

What I think is the display for total amps put into the battery (CAP 36mAh IN) keeps going up as the charger puts more amps into the battery.

The fuel gauge slowly climbs to 100%. Individual cells continue showing 4.206 v/cell. Eventually it finishes and gives me a series of beeps to let me know.

What is the charger doing between the first beep (12.6v) and the second beep (100%)?

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Old 12-16-2012, 12:01 AM   #2
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Hi Mark,

I have a Multi4 as well. (But I have upgraded to a Powerlab 6 this year.) The first beep is when you hit 90% charged, then the series of beeps when complete. The charger "knows" that while flowing current into the battery, the voltage is higher than while resting. So the % charge calculations are not just based on voltage. It must take into account the amount of current that is flowing as well. (And probably a bunch of other things.)

If the charger stopped as soon as it reached 4.20 volts per cell, the battery would actually sag back to a lower voltage and not truely be 100% changed. They slowly ramp the current back while maintaining a constant voltage untill the current is low enough to be considered fully changed. I think that is the last 10% of the charge.

Steve

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Old 12-16-2012, 01:44 AM   #3
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Originally Posted by Stevephoon View Post
Hi Mark,

I have a Multi4 as well. (But I have upgraded to a Powerlab 6 this year.) The first beep is when you hit 90% charged, then the series of beeps when complete. The charger "knows" that while flowing current into the battery, the voltage is higher than while resting. So the % charge calculations are not just based on voltage. It must take into account the amount of current that is flowing as well. (And probably a bunch of other things.)

If the charger stopped as soon as it reached 4.20 volts per cell, the battery would actually sag back to a lower voltage and not truely be 100% changed. They slowly ramp the current back while maintaining a constant voltage untill the current is low enough to be considered fully changed. I think that is the last 10% of the charge.

Steve
Great explantion! I concur! The charge is considered "DONE" when the charge current drops to the charge termination current level defined in the preset. Generally this is C/20 which means (Capacity / 20) or in most cases the set charge current / 20. But this cutoff is adjustable using the CCS application and you'll find the parameter on the Termination tab.

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Old 12-16-2012, 02:10 AM   #4
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Originally Posted by Tim Marks View Post
Great explantion! I concur! The charge is considered "DONE" when the charge current drops to the charge termination current level defined in the preset. Generally this is C/20 which means (Capacity / 20) or in most cases the set charge current / 20. But this cutoff is adjustable using the CCS application and you'll find the parameter on the Termination tab.

Tim Marks
Tim,

I also have a Multi4 and use a CCS. You say the termination current level cutoff can be changed but what is the advantage or disadvantage?

Allan
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Old 12-16-2012, 05:34 AM   #5
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Originally Posted by swimmer View Post
Tim,

I also have a Multi4 and use a CCS. You say the termination current level cutoff can be changed but what is the advantage or disadvantage?

Allan
Hi:

Good question. The lower the current falls off at the end of CV mode, the more electrons you pack into the cells (without over-charging because you're always going to regulate the per cell voltage), the better the pack will be balanced, and the less the cell voltages will sag after the charge is DONE.

Example:

Termination set: C/20

Charge rate set: 2A

Charge will go until current drops to 2A/20 = 100mA

Termination set: C/10

Charge rate set: 2A

Charge will go until current drops to 2A/10 = 200mA

C/20 termination will result in a fuller, more balanced charge. The price you pay is the charge will take slightly longer.

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Old 12-16-2012, 10:04 AM   #6
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Thanks guys. I trust the charger to know what it's doing, but I was curious just what that was.

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