Chosen Solution
I am getting 2 volts DC out of the terminals in the charger for a roomba robot 621. It is that correct? What should it be? Thanks
@decolores add some images showing us where you are measuring. The DC output on your power supply should be between 21V and 24V. Your battery voltage should be between 15.5V and 18V. This could be an issue with the power supply. Adding images to an existing question
I have just been working on a base station. The power supply PCB inside these is not a normal, constant voltage power supply. It is a constant current supply. It supplies 1.2A at up to 22 volts. If you use a power supply that supplies more than 1.2 amps, the Roomba will stop charging with charging error 2. The roomba does measure the charge current and stops charging with that error if it is too high. As for the voltage across the terminals - I would expect that it puts 2 volts across it to detect the vacuum. Once it detects it, it then provides the voltage to charge the battery. I have been unable to locate a replacement power supply PCB for the base station, but there are power adapters used in more modern ones, but I don’t know if they would work if wired in. I have ordered a replacement dock - running it off an adjustable step down adapter is a bit messy.
