Hello,
My Robot hat (V4) on Picar-x lately has not been able to boot-up the raspi 4b. It has worked plenty before now. When I plug in the power cord and flip the switch for the raspi, it will make a clicking sound and jerk a little as if it is trying to start a motor. However, it should not be doing this yet because it has not booted the raspi . The raspi is fine as I can plug the power directy to it and it boots. I wanted to just replace the hat but Sunfounder website shows out of stock and not sure if or when available again.
Please provide us with a video of the issue.
It’s possible that the battery has been completely drained.
Please use a multimeter to measure:
The total voltage of the battery.
The voltage of each individual cell separately.
While the device is turned off, connect it to a Type-C charger to charge the battery for 2 hours. After that, measure the battery voltage again.
Please observe the indicator light status during charging:
A solid red light means the battery is charging normally.
A flashing red light indicates a charging abnormality, meaning the battery is not charging.
After charging for 2 hours, unplug the power supply, turn on the expansion board’s power switch, and check if the battery level indicator lights up.
Please compare the battery voltage before and after charging.
robot_hat_at_raspi-reboot.MOV
Video link of issue provided. Attached photo of restart after charging. The battery before charging was 2.84v on each cell and 5.6v total. After about 2.5hrs of charging, they only got to 4.12v each, 8.24v total. The charge led was a solid red. I unplugged power and flipped the switch and things booted ok this time.. I think the battery level indicator lit up I believe. However, I am not getting to 5v per cell. Does Sunfounder sell that battery replacement ? Thanks for the quick-response help
Your battery is functioning normally.
Key Voltage Specifications:
A single fully charged lithium-ion cell should measure no higher than 4.2V.
Two cells in series have a combined maximum voltage of no higher than 8.4V.
Your Device Setup:
Your device uses two 3.7V Li-ion cells in series, for a nominal total of 7.4V. The readings of 4.12V and 8.24V per cell and in total are normal, near-full-charge voltages.
Understanding the Indicator & Voltage:
The constant charging light is likely normal during the trickle/float charge stage and not a fault. The 5V mentioned is the regulated output voltage supplied to your device (like the Raspberry Pi) by the power module. The battery itself is not charged to 5V.