the battery pack from the iRobot with a much more efficient one. Even though it uses very simple batteries Ni-MH that are quite safe it still has three safety features and NTC, a safety switch and a resettable fuse.

the battery pack of the iRobot braava
the iRobot braava battery pack without its protective sheet
the battery pack of the iRobot Braava is made of six rechargeable batteries of 1.2 volt each totaling 7.2 volt
the white rectangle is a circuit breaker or a resettable fuse
this would be an NTC resistor of 10 kohm.
there is an additional safety feature which is a switch that goes off if the temperature exceeds a certain temperature
Using a lithium ion batteries it lasts much longer. But it definitely doesn’t look good. Also don’t do this at home this is just a demonstration a not for a frequent and normal use