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Hi everyone,
my setup is a Raspberry Pi Model 4B with a WittyPi L3V7 and a battery attached. Additionally i have a USB touch screen connected to my Raspberry Pi.
When i have the 5V USB connected to the WittyPi everything works like a charm but when i then disconnect the power i'd have expected the battery to take over any my PI including my screen to stay on. However, both devices immediately turn off when i disconnect the power.
I've tried this without the screen attached and then it works again like a charm.
Do i have to configure some special settings in the WittyPi to get my setup to work or is it just not possible to power the Pi including a screen via the WittyPi battery?
For details i have the following devices:
- screen: https://www.amazon.de/dp/B0D2QTZRPP?ref=ppx_yo2ov_dt_b_fed_asin_title
- battery: Panasonic NCR18650GA Lithium-Ionen Akku, 3450mAh, Flat-Top
- pi: 4 Model B
Thanks in advance
Posted : 21/10/2024 6:28 pm
I think it is better to first figure out how much current your setup actually consumes on 5V. You may use a USB current meter to find out when powering the device via USB 5V.
When powering the deivce with battery, the actual current from the battery will be about 1.35 (5/3.7) times that current. If your battery could not deliver that much current, its voltage will drop immediately and the deivce will be off.
Witty Pi doesn't know about the peripherals you connect to your Pi, and hence it can not control whether or not to power the screen along with your Pi. If the battery can not deliver the required power for both your Pi and the screen, you may consider adding a control circuit to cut the power for your screen, when the device is powered by battery.
It is possible to check I2C register #7 to know whether it is currently powered by battery.
Posted : 22/10/2024 11:28 am
lbachert reacted
Topic starter
Thanks for that answer.
I've read that the WittyPi l3v7 only supports battery sources with at most 3.7V. If that's the case i don't have a possibility keep both my Pi and my screen running in battery mode?
Posted : 22/10/2024 1:44 pm
@lbachert Witty Pi 4 L3V7 can only work with 3.7V Li-Po battery, which can reach 4.2V after being fully charged. Witty Pi 4 L3V7 has on-board DC/DC converter and can convert the battery voltage to 5V for Raspberry Pi and its peripherals (up to 3A).
Whether this setup is possible depends on how much current is needed by the screen, and how much current can the battery deliver.
Posted : 22/10/2024 5:15 pm