Context
I’ve been keeping the charger tethered on the SUPPLY mode while using Stretch, but this evening I started to hear an intermittent double beep sound suggesting that the battery voltage had dropped below the low voltage threshold (as per Battery Maintenance Guide - Stretch RE1 - Hello Robot Documentation). When I then plugged in the charger in 12V AGM mode, I saw the charger switching off intermittently as shown above.
Questions
Is the discharge despite keeping the charger attached in SUPPLY mode expected? Or does this suggest some other issue with the charger.
I have now placed the charger in SUPPLY mode again based on the instructions for recovering from low battery voltage. But if there is an issue with SUPPLY mode (since the charger was in this mode all through Stretch’s usage), I’m not sure if this will work. What are some ways to debug what the issue might be here? Or to make sure that the SUPPLY mode (and the charger generally) is working correctly? I’m curious if there are some quick ways since waiting for the charging to finish could take 4 to 8 (or more) hours.
Thanks for the writeup and the very helpful .gif. That behavior (bouncing rapidly between standby and AGM) isn’t something I’ve ever seen before.
The first thing I would check is that all of the cable connections between the battery charger and robot are secure and not loose. The behavior in your video is what you might expect to see from an intermittent connection - the charger will enter and fall out of AGM mode based on whether or not it detects a battery attached, so if the connection is poor it might bounce back and forth between standby. In Supply mode this will not happen - you can unplug the robot and the charger will remain in Supply mode - so a poor connection could also explain why your robot batteries started to run down without your noticing. I would unplug, inspect, and securely reattach the two sets of connectors between the robot and charger, as well as the connection to the robot. If the AGM bouncing behavior disappears, that was probably the issue.
You could also unplug the charger from the robot and use a multimeter or oscilloscope to check the voltage output out of the charger in Supply mode - it should be a steady, consistent 13.8 volts. If you are not getting good voltage from the charger and the cables/connections don’t seem to be the issue, it could be a hardware failure in the Genius10 itself, and we can ship a replacement.
It is relatively normal to run the robot until the low-battery beeping warning begins. If you did not run it for a long period of time after this, and especially if the battery voltage did not get low enough to cause a system crash, you should be within the expected range of operation and the regular charging procedures and timing of ~2-3 hours likely still apply.
