Since the mini DIN power is limited to 250ma, has anyone found a way to tap the battery to supply power to added electronics?
I'd prefer this over adding a secondary battery and separate charger
Thanks, Frank
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1 Answer
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We have tried it and have a stably working system using a DC DC voltage converter directly off the battery. We have seen issues though where it will try to run the converter even when the 14-18v battery is at 4 volts so can extremely deep discharge the battery.
If you do this, I would suggest calculating your max current load you want to run and validating it won't over-tax the battery in an un-safe way or have significant spikes in power that will be a problem across the system.
Buffer voltage + UPS battery
Therefore, we introduced a buffer inbetween (OpenUPS or battery backup battery) to buffer it, clean things up better and allow the computer to function without the create being powered.
Compute platform shutdown on low power
We also set up an automatic shutdown of the laptop if voltage becomes too low and "return to dock" commands after 15 minutes to make sure it re-charges itself as regularly as possible if not being actively used.
Check charge regularly on charger
Additionally, we found that on the charger, when in trickle charge mode, the system does not actually test the voltage (Expects it to always be full), so the computer will discharge the battery and it won't turn the charger back on. You therefore have to pull it out of passive mode and then trigger it again (Back out then dock and charge) and it will correctly check the voltage and charge.
State
This is currently not a fully tested system, but have have tried it on multiple create 2's / NUC's / Laptops and have had the system recharging itself for 10+ days in a row while powering lidar, camera, NUC, create, etc.
If you try this, would love to hear how it goes for you and improvements you see as valuable.
Please also just be careful and have a fire extinguisher near-by. ;-)
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$\begingroup$ Wow! I am really impressed by al the testing you went through. Thank you! $\endgroup$– FaengelmCommented Apr 4, 2018 at 1:08
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$\begingroup$ I also had setup a similar approach using a dc-dc converter and was running a smaller load consisting of an iPad and an EZ-Robot. $\endgroup$– FaengelmCommented Apr 4, 2018 at 1:11
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$\begingroup$ @faengelm would love to hear how it goes for you and any issues you encounter. $\endgroup$– hcl337Commented Apr 4, 2018 at 23:06
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$\begingroup$ I know this is several years old at this point, but I'm trying and failing to do the same thing here. Could you elaborate on your procedure to force the Create2 to switch from trickle-charge to full-charge mode? I'm currently using the ROS create_driver and switching from Passive->Full->Passive does not seem to change anything (charge level is still incorrect) $\endgroup$– MindS1Commented Feb 15, 2022 at 21:21
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$\begingroup$ This was a long time ago, but my memory is that we created a watchdog timer every N minutes to toggle the robot into active state for a period of time to wake it up and then a few seconds later gave it the command to go back to sleep and start charging again. We had to fork the create driver. Looking back, I would suggest using the Kabuki instead as it is not much more expensive and has stable charging. We spent way too much time debugging a system which wasn't designed for long-term active use. $\endgroup$– hcl337Commented Feb 17, 2022 at 15:41