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Multimeter readings way off from Blue Smart charger settings

Hi. I have a 200Ah VRLA acid battery and Blue Smart IP22 charger 12/20A (3) hooked up 24/7. Latest firmware (I think 3.42..).

In any of its automatic charging phases, readings from a multimeter are off by a great margin - 0.10 to 0.20V. When in Bulk mode its about 0.1, and in Float/Storage, close to 0.2V. Tried three multimeters, they are correct, one is not cheap. I hooked up an oscilloscope and there I can see considerable ripple (maybe about 100 mV) but I can calculate good voltages that correspond closely to what's supposed and what on the app screen (14.4 or 13.8V). Why this discrepancy between multimeters and what's on the smartphone screen (and what's supposed to be by the currently selected profile)?


Err: The scope is about 0.1V off when calibrating with battery. Then the charger is approx. 0.15V off from what it's supposed to output at almost any moment! When the current is higher (1-2A+), the voltage seems much closer to the supposed value.

chargerBluetoothbluesmart ip22
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