More about grading function on some XTAR chargers

XTAR Light

XTAR Light

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Apr 26, 2010
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China
A few customers asked the question about VC4S grading function before. "If I test the capacity of a brand new rechargeable 18650 battery on the VC4S, will it show similar capacity numbers regardless of what slot it's in? And how about the accuracy of this grading function? "

There are more info about it. A grading sequence on some xtar chargers consists of charging the battery, discharging it (generally to 2.5V-2.8V) while measuring capacity and then charging it again. The way of these chargers testing mAh is usually by using a current shunt and an internal clock. The slots on chargers have their own current shunt. And those PCB current shunts are usually slightly different in resistance, which causes differences in capacity ratings when the battery is tested in different slots. Even with calibration, there will be a little changes due to heat generation on the PCB, among other things.

Users probably get battery capacity readings that are within 10% or so of each other. Factors affecting the grading function, may include what temperature the room and batteries are, in combination with the small differences in shunt resistance...
 
KITROBASKIN

KITROBASKIN

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Good to know, and wondering if the connection between the battery ends with the charger contacts may also play a role: whether from varied resistance of the battery/slot surfaces or the strength of the spring in each slot.
 

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