GoPiGo Power management issue

Going forward with the integration of my GopiGo2/Pi3B+ Raspbian for Robots OS with Google Cloud API, I’m experiencing some issues that I want to share with forum in order to understand if somebody else has already figure out a solution.

First, when I coding having pi3b+ powered via usb no issue at all. Power stability is ok, but commands that I send to the motors and servo don’t have the same effect. For understanding, running the command left() with time.sleep(0.5) generate a longer rotation when GopiGo is on battery rather then when is plugged on the Pi board. Of course there is a difference of voltage between energy provided by usb and battery through gopigo card, my question is if you all you guy have fixed it only via coding or by plugging a power supply through gopigo card…

Second, and this is a real problem, for some reason and I don’t know why after 10 minutes on battery the system becomes to be not stable and by connecting a monitor on hdmi board I see that raspberry is keeping rebooting itself.

At that point I have turned off the system. I have restarted but after a minute became unstable again. I guess some hardware issue may be involved.

After 15 minutes I have tried again and now the system seemed to be stable back on battery. The voltage measured was 8.7V.

Any idea? (thx)

It sounds like tired batteries:

  • Strongly suggest 8x Eneloop White 1900mAH NiMH cells - you will get a solid 5 to 6 hours run time.
  • Suggest a BT-C2400 Battery Charger Analyzer Tester to test and recondition if needed

DI does sell a good smart charger but their rechargeable battery pack is returning 404 page not found at the moment.

Sorry I didn’t get time to run the test you sent me. I have just took a look to code. Interesting. The issue I have described happened in different occasions. I have currently some sensors installed on gopigo but were not part of my test except the ultrasonic.
By the way, when I had the issue I have duracell batteries.
Hovewer, I have even rechargeable Ni-mh 2900mAh, the brand is Join

When those are new you should be seeing 4 to 6 hours of “just sitting there reading a sensor every once in a while”. (Pi3B+ idle draws 30-40% more than my Pi3B non-plus version)

After a while, the “playtime” will start decreasing and eventually one or two of the cells may not hold much capacity even though they charge up to the full 1.4v state.

I had one set last 55 cycles till half idle playtime, and another set last 150 cycles. Interestingly, the 1900 mAH class of NiMH cells start out with less play time, but go for more than 300 cycles before starting to decline.

New Batteries(7): Jan 18 2020 Eneloop (White) $25.70
“up to 2000mAh, min 1900, up to 2100 cycles”
Initial 6.4 hours
300 cycles: 6.3 hrs (98% Apr 24 2020)
(Still going …)

New Batteries(3): Apr 2019 8x EBL 2800 mAh AA cells
Initial 8h playtime (to 8.5v)
Jul 2019 4.5 hours playtime to 8.1v reading
(~150 cycles to half playtime)

New Batteries(2): Sep 2018 8x EBL 2800 mAh AA cells
New: 9h 20m to 7.4 cliff
(~55 cycles to half playtime)

I do remember someone posting about an ultrasonic sensor getting hot - perhaps it is drawing too much current - it is only supposed to draw 15mA which should not get hot and it should not shorten life very much.

Another thing - you do have some time.sleep(1) or so to keep the processor from eating up your batteries - right? (check that uptime command to see what your load averages are.)