Are there power banks (portable battery powered USB supplies) that can be used as a UPS?
The problems are:
some require a button to be pressed, to start the output
some assuming they are ONLY charging a battery and may quit supplying current when the load falls below a threshold
I think the key word is “pass-through”, that is supposed to mean they can charge and discharge at the same time
But they would also need to satisfy 1. and 2. above…
(What is the use? USB powered cameras, for instance, for security systems… internet routers. (so you still have a phone if your phone is via internet).
So instead of powering via the regular USB 5V supply, you would use one of these things instead.
Would also be nice if they were cheap.
I’ve seen things on Amazon in the $40 range, that is too much.
The TP5100 chip used in the BLF LT1 lantern for charging can input/output at the same time. In fact, the lantern will be able to work without batteries if a power supply is plugged into the USB charging port.
I think the gen2 xiaomi 20,000mAh have 5V pass through but not sure if there is a switching
when input power is disconnected. Most UPS doesn’t have switching but DIY solar controller + 12V battery charger 2in1 does. I can check it out and let you know which powerbank in my collection have non-switching pass through (always on or separated buck-boost controller).
I have tested these DIY powerbanks below if they can be UPS for RPi, Routers, etc.
1. Tomo PowerBank S4 (4x 18650; Similar to M4/M2; 5V/1A input) - Can do pass-through charging but does not seem to be able to charge the battery while using the output, this maybe due to input power limited to 1A. Unplugging the input power does not cause a surge on the output USB.
2. Soshine E3S-QC (4x 18650; QC 3.0 on USB Out 2) - Can do pass-through charging, but unplugging output causes a less than a second power surge before switching to battery. While pass through charging, the USB output port 1 (5V/1A) is turned off.
3. Epilot E4 (4x 18650; 5V 2A input) - Similar to Soshine E3S-QC, but can still provide power to both USB outputs on pass-through charging.
Battery arrangement is 3S2P, but if I were to buy one I'd make windows on the cover and install more batteries (of course all soldered or spot welded).