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steve.taranovich
steve.taranovich
2/27/2019 3:45:24 PM
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Blogger
Re: balance during charge/discharge?
@Michele Kinman---thanks for that clarification Michele!

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Michele Kinman
Michele Kinman
2/27/2019 3:00:57 PM
User Rank
Newbie
Re: balance during charge/discharge?
SABMB6 board only balances supercapacitor leakage current. It does balancing charging and discharging current. Additional technical data is available at www.aldinc.com 

 

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Hooey0
Hooey0
2/27/2019 11:45:13 AM
User Rank
Teacher
Re: balance during charge/discharge?
DaveR1234 - Your question comes up quite frequently. As you correctly noted, these FETs are neither capable of, nor intended to carrying either charging or discharging currents. They are only there to balance the leakage currents. The leakage current in a particular supercapacitor, or any capacitor for that matter, can vary from capacitor to capacitor, and also with lot, time, temperature, phase of the moon, etc.

It's no different than when you have a high voltage application and you only have lower voltage rated capacitors. When you stack the lower voltage rated capacitors in series, you need a properly sized and rated shunt resistor across each one in order to to balance the input high voltage across each. That way, none of the capacitors will have a voltage applied to them in excess of their rated value.

If you check out the higher voltage supercapacitor modules, they will specify the "standby current". This value will give you a clue as to whether the balancing is active, as in the FET configuration, or passive, as in the shunt resistor architecture. The shunt resistor architecture is typically more reliable, given proper resistor selection, but comes at a cost of a higher standby current.

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DaveR1234
DaveR1234
2/27/2019 9:55:04 AM
User Rank
Newbie
balance during charge/discharge?
Unless the balancing FETs are big, it doesn't appear that they can maintain balance during charging and discharging.  In an automotive application, these currents can be in the tens or hundreds of amps.

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