• 1
    The missing charger
    First step of diagnosis was ordering a new power supply for the dyson DC16, since none was to be found in the scrap yard. The vacuum uses two metal contacts on it's underside to be slided into a charging station. The powersupply is 28V 700mA which was nothing I had at hand, so I had to order it. Together with some contacts from a car cigarette lighter plug and a printed case I could assemble a charging station. So the vacuum was charging and working for a couple of seconds, but displayed a dead battery immediately afterwards. There are replacement batteries, but I am truly not a fan of cheap chinese replacement batteries of unknown quality, so I figured I'd build my own since I had some laptop cells at hand.
  • 2
    Old batteries are old

    Getting the battery pack opened was not as easy as I thought. The visible tabs put up quite a fight, but I was able to open it without damaging anything. To my surprise the battery pack had no balancing circuit at all, despite it being 18650 Liion cells. Only Plus and Minus and a temperature sensor are on the connector of the battery.

    Since I had some batteries from a Thinkpad Battery at hand, which suddenly died on me, I was planning to build a new battery out of those. I discharged and charged all cells, matched capacities aaaand completly forgot about internal resistance... Since the vacuum is pulling 200W form the 6S battery pack, I should have been concerned by this... As an improvement to the original battery pack I included an battery protection and balancing circuit I found on Ebay. I also bought a cheap pcb spot welder which I connected to a car battery. It works quite well!

    I performed the first charging of the new battery pack on an old grill in front of the house. If it goes up in flames, at least it's outside, but everything went well.... expect.... it still showed the same error. So I tested out other known errors of the dyson DC16, but everything seemed to be working fine. Then I had the bright idea to actually measure the voltage of the battery pack under load and surprise surprise the voltage brakes down. So I now had two dead battery packs.

  • 3
    Go big or go home
    Even though I would have been able to replace the original cells with new 18650s and a balancing circuit in the original case, the required high current cells would have been quite expensive for a fun project with unknown outcome. So I decided to use 21700 which in general have higher current ratings due to the greater diameter. This meant printing a new case. I could have integrated the sliding mechanism seen on the top with the hook, but printing such delicate features with FDM seemed to much of a hassle and since the original case was to be thrown away either way, I packed out the saw. I sawed out the top piece of the original case and glued it to mine, reusing the connector which is put on the right side of the case.