Post Mortem of a robotic vacuum cleaner

I was told about this robotic vacuum cleaner with the symptom "not charging" and if it's of any interest to me, its mine!

Hey, a geek would never say no to a new toy, right? Moreover i'm secretly a fixer; one that is deeply curious about the WHYs and the endless (sometimes foolish) attempts to fix instead of the usual \ just throw / buy / why bother /.

robot

guess who is getting stripped today

tools

Having all your tools handy (omg so punny) makes a teardown easier. Yes, you need cold drinks to keep you going.

bottom-view

Always looks for the largest screw and the most obvious ones to be first removed.

innards

Did not take more than 10 minutes for the top cover to be removed.

controller-board

The electronics board is surprisingly well designed and spots a clean layout. The brain is a STM32F030 but i shall not go into the details (for now).

battery

Since the initial diagnosis is "not charging", the direction that i headed in was to determine if the batteries were dead. I did a simple voltage measurement and it says "0V".

OH NO... Ok side track... Luckily the robotic cleaner powers up fine (sings and lights up) so you know nothing is burnt and chances of fixing it is high.

I measured the resistance of the battery and it started doing something weird..... 600Kohms... open circuit, repeat.. Aha! digs further

battery stripped

Removed the clothes of the battery and you see those typical 18650 Samsung batteries which tells you that at least they did not use some cheapo ones that may cause a fire. Hooray responsible designers!

battery charger

Here comes another handy tool that allows me to charge and at the same time determine if the batteries are really dead!

fuel-status

Definitely doesn't bode well with a 0% battery but it managed to charge. :)

fuel-83

83% yay! At this juncture, i must point out that i headed in the wrong direction as the individual batteries had voltages but not the red/black wire. I should have realized that something is not right with the battery circuit

rubber-band-fix

Here's a tip! Rubber band saves you the pain of having to constantly hold the wires in place during a temporary fix. :)

battery-circuit

Yes...I checked every passive component on the circuit and there's a dead 1Mega Ohm resistor. Definitely not something intuitive and it's experience that told me, hey, check those cute guys out!

test-points

OH YES... I saw many test points too. Which means in no time, i can modify the vacuum cleaner and make it do more awesome stuff. :)

You know, it is only through doing that you gain the experience, and the experience is what makes the next doing easier.

Happy hacking!