KanoMaster22 wrote: ↑
Thu Jun 14, 2018 11:20 am
Okay, so the batteries contained inside this power bank are 3.7V what could go wrong if I connected one of these to a board like the Zero Lipo or an Adafruit Feather?
They are not 3.7 volts. Rechargeable lithiums are 4.1 or 4.2 volts when fully charged. The voltage falls as charge is expended. Typically you should stop taking current from them when the voltage reaches the region of 2.6 to 3.0 volts.
While some RPis may work OK with such low and changing voltage compared to the specified 5 volts, any attached peripherals may not.
An additional advantage of keeping the cells in the powerbank is that contains a circuit for safely charging the cells and a circuit to prevent them being over-discharged. Lithiums are dangerous* if not charged properly and over-discharging damages them.
(* risk to property, limb and life in respect of which your insurance company might refuse to honour a claim.)