Looks like a Diode, 0,438V Drop with no battery attached.
Thanks.
What this means is that in a multi battery device, when the first Batteroo shuts down, the current goes through this diode. The device could still keep running as if it uses 4 batteries, the other Batteroos are still providing 4.5v and this diode completes the circuit. If the current was 1A, the voltage drop at 1A may be 0.6V and so there is a 0.6W dissapation in the chip.
How hot does the chip get with a 0.6W dissapation?
It is not that hard to measure as diodes have a reliable -2.1 to -2.2mV per degree C temperature coefficient. So if measure the ambient temperature and do a current versus voltage drop curve, you can convert this to a current versus die temperature curve. If the chip gets to 150 deg C, it is getting close to failure. Usually the chip fuses - it turns into a lump of low resistance metal.
It may be that this factor decides the real maximum current the Batteroo can supply in a multi-battery device.
The other thing that this can mean is that if you put a new battery with a Batteroo in a multi battery device, and put it in a multi battery device as the last battery, and the device was switched on as you are inserting the batteries, it may be possible to cause the Batteroo to latch up - which could cause it to try and pull the battery down to perhaps 1.2V. This would cause the Batteroo chip to overheat, and fail as above. This is a possibility, but the chip could also be a latch-up resistant design which would prevent this condition.
Dave did a video on this latch-up effect with cmos chips:
So here are two possible Batteriser failure modes that do not involve the clip shorting to the battery cell case. Both could end up with a Batteroo that shorts out the battery.