Repair of broken Nao robot battery pack

The battery pack for our Aldebaran / SoftBank Robotics Nao V6 robot broke and we are currently not able to find a reseller that ships to our country. Even contacting SoftBank Robotics directly did not result in any response. The official specifications are available here. Since the battery pack was clearly broken we decided to open it up to be able to find a replacement battery ourselves.

Opening the casing is difficult, since it is not only kept in place with latches, but is also glued together. We used a soldering iron at the seams to open open the case.

The battery back seems to consist of six Sony US18650NC1 2900mAh batteries. They are connected with seven wires to a PCB board. The power supply connects with two cables to the PCB board. In addition, the case has two contacts next the charger plug that could be used for detecting if the battery cover is closed. Five contacts connect the battery pack to the robot of which the first two bigger ones seem to carry the power. The four smaller contacts are probably to communicate with between the robot and the battery PCB board.

We ordered some new batteries and will keep you updated on the developments.

21 thoughts on “Repair of broken Nao robot battery pack”

  1. Hello, I teach at an High school and we are facing same issue. Please let me know if your fix will work. Thank you.

  2. Our battery pack died from lack of use. Replacements online range from $290~$490. Our NAO is a V5, the cells in the pack are grey; CGR18650CH. We’ve ordered 6 with solder tabs.

  3. Hi, is there any update on how it went. I’m curious if I should try to do the same. Anyone been successful?

  4. Hello. Can Nao be use without battery, just on sector ? (if battery is HS)

    My NAO shut down after boot…he say “gniark gniark” and shut down…

    Anyone repair a battery?

  5. Hi. After reading the comment that the batteries were Sony US18650NC1 2900mAh batteries, we ordered 6 from a UK supplier (£8.99 each). The original batteries were connected in series with flat plates which were spot welded to the cells. We soldered the new batteries together with wire as flat as we could and reconnected the wires that monitor each cell, but it was still a squeeze to get them back in the original case and then back into the Nao. Having done that, our Nao is back in action and working fine.

  6. Hi all, We have the same issue, and I found there are some suppliers on eBay and the price is about 450 pounds. Is that reliable or do I have to order some batteries and fix them by myself?

  7. Getting original new batteries would likely to be the best solution, if you can afford it. I found some web shops that listed these batteries, but they did not ship to New Zealand or they would just cancel my order.

  8. We planned to do a school project with nao but the battery is broken so our robot is a paperweight now. There are no web shops at all that ship to the netherlands. Pretty wierd that such an expensive robot has this lack of support.

  9. I do offer a repair service based in the Netherlands. I use quality cells from Sony, Panasonic or Samsung whichever are locally available at that time. Capacities vary around Typ. 2900 mAh, discharge current will be rated Min. 10A. All six batteries inside the pack will be replaced with new (non-refurbished) cells.

    Please contact me, Marco, on naorepair at Makerspace040 dot nl or Whatsapp, Telegram or Signal me at +31 (six) 2035 (zero) 823.

    To get a decent repair service running I need to receive 2 pack from the first repairs and I will return one working pack. Repair will take between 1 and 3 weeks. When sending me 2 battery packs, the repair will be free of charge.

    The individual cells will be properly spot welded and kaptop tape will be used identical to the original battery construction. To open the pack I will have to saw through the clips holding the pack. I will glue the pack together with a 2 component epoxy glue.

    Due to the way I need to open up the glues pack, the structural strength of the battery pack will be less strong as the original. Do not charge or use the battery pack unattended.

  10. Found batteries on Amazon.CA. Not the exact part number but specs look good. Anyone tried them?

    Green Us18650 Vtc6 3.7v 3000mah Lithium Li-ion Battery Replacement Battery

  11. My replacement battery cells have not arrived so I tried to fix them with the process above post from RoboHack forum. It worked! My two batteries are alive again. Thanks for the post.

  12. We have two Nao’s at the school I work for, and I have successfully re-celled both battery packs. I am able to open the battery packs without using a soldering iron, but rather a jigsaw to carefully open both ends of the pack. This allows for neat gluing the top and bottom part together after the repairs.

    I’ve used Sony / Murata 3000 mAh batteries, with maximum discharge rate of 30 A. Hot glued the six batteries together and isolated them with kaptop tape. Further, I used a spot welder to connect the batteries with 5 mmx0.13 mm nickel strips and insulated again with kapton tape.

    The battery pack I made looks pretty exact like the one originally used, and finishes charging in about an hour.

    just like Marco van Nieuwenhoven listed above, I am willing to provide the repair services to other educational institutions (in the Netherlands) for cost-covering prices.

    For further information, contact me at info at coderclass in the Netherlands (from this info you can make the e-mail address)

  13. Above I have offered a repair service.

    Due to circumstances responses to messages and repairs were taking unacceptably long. My apologies for those who were involved. Currently I am not accepting new repairs.

    I will resume the repairservice, but it will probably not be in 2022 anymore. A customer has asked me to make a mains connected battery pack, which does not contain any batteries. I will investigate this in 2023.

  14. We should actually design 3D printable cases for the battery pack to increase maintainability. I don’t understand why the manufacturer made the case so that you have to saw it open…

  15. So true, Ramin,
    Just like you I have been looking for a printable case which isn’t there. Up to now I only repaired two batteries, but if the need arises I will look into modelling it in Fusion 360 and making it available to all, to make it better serviceable for the future. Opening the glued battery case a second time will probably make the battery case useless, so the need for a printed battery case will probably come somewhere in time.

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