The spec sheet for the IO Pi Plus states that there is a maximum of 125ma for all i/o on each chip. If I understand it correctly, it implies that an input (applying 5v to a pin) will draw 25ma. Thus, there can be a maximum of 5 positive inputs, out of 16 potentials) at the same time.
It also seems that it is impractical to drive an optically-isolated 8-relay bank at 20ma per channel, if all relays could be active at once.
Is this correct, please, or have I misunderstood?