How do I apply a load test to a Roomba or Scooba battery ?
This picture shows a 12 volt 20 watt electric light bulb part number (MR16) connected to a Roomba battery using test leads with alligator clips on each end. The test leads can be purchased from your local electronics shop or Radio Shack. The lamp is positioned on top of a ceramic coffee cup since the lamp will get hot when connected to the battery. This particular test involves a 3.2Ah Roomba battery with a voltage level of 16 volt. This will create a current load of approximately 1.87 amps. The Roomba will draw about 2 amps under normal load conditions so the test setup is very similar to an actual load that a Roomba would experience.
The actual electrical connection is accomplished by cutting two short pieces of insulated solid copper wire (20 ga). I used Red for (+) and Black for (-). Connect the Red copper wire to the battery terminal that is furthest from the battery case and connect the Black copper wire to the battery terminal that is closest to the battery. Then connect the two alligator clips to the copper wires and finally connect the other two alligator clips to the 12 volt lamp.
Once the electrical path is complete the lamp will turn on and should stay on for at least 2 hours. If the lamp does not last that long then your battery is defective. This load testing of your battery should not be left unattended and the voltage level should be monitored to make sure the battery voltage does not drop below 12 volts.
Finally, if you don't have a digital multimeter to monitor the battery voltage level during the load test then please invest in a $10 DMM from Radio Shack or elsewhere or do not proceed with this load testing.
How do I measure battery voltage on a Roomba or Scooba ?
You can head down to your local electronics shop, (I use Radio Shack) and purchase yourself a low cost Digital MultiMeter or you can order one from me for $10 including USPS shipping, just paypal me at firstname.lastname@example.org. Connect the Red (+) lead to the positive terminal on the battery and connect the Black (-) lead to the negative terminal. Turn the meter on and set it at the 20 volt dc scale. The battery should indicate between 16 and 17 volts if properly charged. The picture represents a Scooba battery but the same connections are done when measuring a Roomba battery.
How do I test a 5XX Wheel Motor ?
The first components that one will need in order to test the Wheel Drive Motor either Left or Right is a working 9 volt battery and a 9 volt battery cap with the positive and negative leads attached. The cap will snap onto the top of the battery and then the leads will have battery potential and all that is then required is the actual electrical connection to the motor.
In addition to the 9 volt battery and 9 volt battery cap, life can be made easier when testing by obtaining a couple of small test leads with clips. Once the test leads are connected to the motor leads the motor should begin to rotate. If the motor fails to rotate verify that you have made good electrical contact to the two solder joints on the PCB. You can also attempt to rotate the wheel by hand and see if the motor will take over and spin the wheel. Once that is accomplished if the motor runs you can reverse the two leads and the motor should run in the opposite direction. If the motor still will not function verify that the electrical wires on the PCB are making good contact and that the wires are not broken either at the PCB end or at the Paddle Board end of the same wires. If excessive resistance is felt when attempting to rotate the wheel then you will need to dis-assemble further and inspect the drive motor gear assembly.
Use caution here when removing the screws that hold the gear access plate. The very top two screws are phillips head machine thread screws that hold the electric motor in place. Don't get them mixed up with the lower 4 phillips head self tapping screws. Once all 6 screws are removed the cover can be opened.