Electronics > Repair

AC to DC converter half voltage

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sdancer75:
Here the backside of the DC converter PCB

wasedadoc:
The diode immediately behnd the barrel jack is a half wave rectifier and there is no reservoir capacitor.  So a meter showing around 7 Volts is to be expected.

J-R:
What is the DC voltage displayed on the DMM when the battery is also connected?
I would suspect a bad battery at this point.  Is it SLA/AGM or perhaps NiMH?

wasedadoc:
Yes the voltage when the battery is connected will be informative.  Even though the meter is showing a little more more 7 Volts when the battery is not connected (as in the photo) the positive peaks will be about 23 Volts.  When a 12 Volt battery is connected some of the waveform will be above the battery voltage and charging current will flow into the battery during those periods.

sdancer75:

--- Quote from: J-R on June 07, 2023, 07:34:34 pm ---What is the DC voltage displayed on the DMM when the battery is also connected?
I would suspect a bad battery at this point.  Is it SLA/AGM or perhaps NiMH?

--- End quote ---

1) The DC Voltage when the battery is connected, is a little bit higher ~8V
2) The battery pack is  18650 Li-ion with Lithium Battery Charger Protection Board 18650 BMS (photo attached)


PS : How to know if a battery is bad? Currently, they are all discharged.

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