I am having trouble using 12V input to the UPS hat on J4, with the UPS hat attached to a Raspberry Pi 4B+. My symptoms are as follows:
- From 5V to somewhere around 8.5V, the UPS Hat functions as I expect, and the RPi boots, whether there is a battery installed or not.
- With a battery installed, the UPS Hat functions as expected including J4 input voltages up to 12V.
- Without a battery installed and input power >8.5V, the Hat initially outputs 5V for 5-6 seconds, but then the output power abruptly drops to 0V. Obviously, the Pi does not boot fully.
I’ve seen this behavior on 100% of the Hats I’ve looked at so far (4 total.) Is the UPS Hat not expected to function above a certain input voltage without a battery (and if so, can you please tell me why?) And if this is the case, is it likely to function with a dead battery installed? I plan to use a battery, but my systems will be in remote locations, possibly powered down for long periods of time, so it is possible the 18650 will be fully drained when input power is applied.