Quote:
Originally Posted by MetroMPG
So with the Super Brain setting at "5 mV per cell peak detection" for charging the 6 cell subpack, it waits until it detects a voltage drop of 30 millivolts or more (30 = 6 cells times 5 mV) from the highest peak seen so far before concluding the charge cycle.
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Shown bellow are some of the common end of charge detection methods different NiMH chargers use.
I suspect the Super Brain also uses some of these other methods as fail safes ... for instance it has an optional temperature sensor could potentially be used for the dT ( change in Temperature ) , and the dT/dt ( Change in Temperature per unit time ) , and the TCO ( Peak Temperature Cut Off ) ... I suspect it also has a maximum peak voltage based on selected chemistry and selected number of cells ... but sense it tracks voltage and current over time ... it could potentially be doing any of those methods ... including the CV@CC ( Constant Voltage @ Constant Current ) , at a CC the voltage will eventually level off ... if +dV or -dV are too small to detect the CV@CC can still be detected.
A side note ... a less common method deployed in the IC4 NiMH batteries ... is the change in internal pressure detection ... as non-charging chemical reactions being to dominate the reactions the internal pressure also increases ... the IC4 NiMH cells used this with a internal resettable pressure switch as a fail safe ... and the Prius NiMH cells don't detect the pressure change ... but the battery pack is designed to reenforce the plastic NiMH cells cases ... which if not thus reenforced would swell outward with the increasing internal pressures ... so they reenforce the cells from the outside ... while Panasonic in the Honda design instead uses a stronger metal cell casing to contain the changes in internal pressure.
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Unfortunately ... all of these methods have a good chance to do some amount of overcharging ... the up curve in the dV bump going up and then back down ... is a symptom of the dominate chemical reaction in the cell changing from a charging one to a over charging one ... the up swing in the temperature slope is also a symptom of the dominate chemical reaction in the cell changing from a charging one to a over charging one ... so unfortunately all the commonly used end of charge detection methods for NiMH look for things that only show up when the dominate chemical reaction is no longer a charging one... but NiMH is a abuse tolerant battery chemistry ... so speed of charging is usually a greater concern than battery cell service life , which is why these common charging methods are common.