I have two Roomba Discoveries, a 4220 and a 4221. Both have a problem with charging it seems. They will reach green afer the pulsing charge indicator (though one is very dim), but then when unplugged, they will not turn on at all.
I have tried:
buying new batteries (3 different ones)
doing the battery reset procedure (hold power for 5-15 seconds with battery out, replace battery, plug in directly and charge for 72 hours) multiple times
testing my chargers. Both have ~22.5 VDC
When I first got them, they ran fine for the first run, and then had this problem. I do not know waht the person I bought them from did to make them work, but I can’t’ replicate it. A couple times they charged enough to run for 20-30 seconds, then give the dead battery uh oh and turn red right away.
In this case, it appears that your robots are no longer able to charge batteries. This is caused by an issue with the robots charging system found on the motherboard. We suggest replacing the motherboard in this case.
You may be able to find a replacement motherboard online although these products have been discontinued for several years now.
Thanks. Are there any other model motherboards that are interchangeable? I’ve found a couple for the 4220 but none for the 4221, so I’m wondering if I can use a 4220 for both, or other 400 or 4000 series?
The motherboards for the 4221 and 4220 are interchangeable and will work without issues in your robots. As long as your robot has the same buttons, it will be able to be used.
So I have replaced the motherboard on the 4221, but absolutely nothing changed. THe charging/power light is still dim, and even after it turns a dim green, when I unplug it it won’t even turn on.
It is true that there are different connections depending on the wheel or dirt detector. But, by removing the connector, it is possible to plug in just one dirt detector in one row of 4 pins. It is also possible to plug in part of the swivel or non swivel caster wheel since the robot when updated no longer calculates the wheel rotations for the black and white wheel.
Have you purchased new motherboards or used ones? If the charger and battery are good and the motherboard is new, the only other issue left are the cables going from the motherboard to the battery. This is not an issue we see frequently though. Have you verified all motherboard connections? These blog posts will help:
It is also possible that your faulty charging system has damaged the new batteries. A faulty charging system on the motherboard can actually discharge batteries and cause issues. Do you have a battery you know works properly? Have you verified the voltage of your batteries?
It was a used motherboard from a a unit that supposedly had a non-motherboard related problem.
Regarding the plugs: for the dirt detector, I see that only 4 pins exist on both units, but I can’t see a way to plug the 8 pin connector into the 4 pin socket. Is this possible, or only the reverse? For the swivel, again how to go from the 6 pin plug to 4 pin connector? Also, what do you mean by updated? How would i know if mine has been or requires an update (I’ve never done one).
The charger is good, but I am not clear on how to tell if the battery is good since I can’t take a reading from it when charged. I will go ahead and purchase a new battery in case the current ones i have are damaged. Are off-brand batteries good, or is there really a difference that makes it necessary to buy the $60 roomba branded ones?
Thank you for the info on the motherboard. For the connectors, we suggest to remove the connector on the motherboard and plug only the first set of connectors (top 4 pins) for the dirt detector on the four pins on the motherboard which are now without a connector. This way only one dirt detector will work but, this is OK since all new robots only have one anyway. The second one will simply be unused.
This should also be possible for the swivel sensor. Remove the connector on the motherboard and connect the first four pins of the connector.
iRobot used to have what is called an OSMO updating device that you could insert in the Roombas Mini DIN connector and the robot would update it,s programming. This had the effect to correct some issues with the sensors by reading them differently or not at all.
At the moment, if the robot does not charge, these connections should not cause any issues.
The battery voltage can be verified with a voltmeter on the battery contacts. Under 12V, the robot will usually not turn on or indicate the dead battery song. But, if the battery is old it can show the proper voltage and get drained very quickly with load when the robot starts.
In your case, we are still leaning towards a defective charging unit on the robots motherboard since we cannot be certain the motherboard purchased does not have any issues. re-branded Roomba batteries are generally good but, not from all resellers. Only buy from trusted brands.
We sell a very good battery at a decent price on our website.
If the motherboards you purchased do not have a charging issue, we would suggest trying to charge the new battery with these motherboards. The swivel caster connections should not cause any issues for charging. If it charges, you could then try connecting the swivel connectors and see how it goes from there before buying another motherboard.
