Your NAO’s battery isn’t dead.
It just needs rebuilding.

Usually not. When a NAO pack sits uncharged for a long time the cells fall below their safe minimum and the battery management board latches into a deep-discharge protection state. Once locked, the pack will not accept a charge no matter how long you leave it connected, and the robot appears completely dead. The robot itself is normally fine — the pack needs rebuilding and the BMS needs to be brought back out of lockout.

The board can be brought back out of its protection state, but the cells that triggered it are no longer trustworthy. Cells taken that low suffer permanent internal damage and can behave unpredictably afterwards. That is why the service replaces all six cells rather than trying to nurse the old ones back — the safe fix is new cells behind a working BMS.

NAO V4, V5 and V6, which all use the same six-cell 21.6 V lithium-ion architecture, in both the 48.6 Wh and 62.6 Wh capacities. For older V3.x packs, get in touch first so I can confirm the revision before you ship.

All six, every time. Mixing new cells with aged ones creates a pack that drifts out of balance quickly and fails again sooner. New cells are capacity-tested and matched to each other before they go in.

New, brand-name, high-drain 18650 cells rated well above what NAO draws. Nothing reclaimed, nothing pulled from another pack.

No — send the battery pack only. It comes out of the torso without tools. Keep the robot and the charger with you.

The pack is rebuilt and shipped back within two weeks of reaching me. That window covers diagnosis, the rebuild itself and the full test cycle — it does not include the time your package spends in transit on the way to me. You will hear from me at each stage: when it arrives, what I find when I open it, when it goes on test, and when it ships back with the tracking number.

$250 per pack, flat. That covers all six new cells, the BMS recovery, the balance charge, the full load test and return shipping to your US address. There is no separate diagnosis fee and no parts surcharge — one price, whatever the pack turns out to need. You are charged only after the rebuild is finished and confirmed working: nothing up front, and nothing at all if it cannot be fixed.

NAO packs are bonded shut at the factory and there is no clean way in, so it can happen. If a shell cracks or chips while I am prying it apart I glue it back, and the pack goes back together sound — it holds, it seals, it seats in the torso properly, and it has no effect on how the battery performs or how long it lasts. What I cannot promise is that it will look untouched.

I replace cells, but I cannot replace the battery management board — it is specific to NAO and is not sold separately. If that board is genuinely damaged rather than just latched into deep-discharge protection, the pack cannot be rebuilt. Sometimes I can see that at diagnosis; occasionally it only becomes clear once the pack is open. Either way I stop there and tell you immediately — and there is no charge. I only invoice once a pack is rebuilt, tested and confirmed working, so you never pay for a repair that could not be done. I will not hand you back a pack that does not work and call it a repair.

Yes. It is built to the same electrical specification — 21.6 V nominal, same charge profile, same connector and cover-detect contacts — so your existing charger works normally and NAOqi reports the battery the way it always did. It drops into the robot with no modification.

I will tell you. You get a message when the pack arrives, another once I have opened it and know what I am dealing with, another when it goes on test, and a final one with the tracking number when it ships back. You are dealing with me directly the whole way through — there is no ticket queue and no handoff.

Deep discharge is what kills these packs, and it is entirely preventable. Fully recharge the battery at least once every three months even when the robot is not in use — that alone prevents most NAO battery failures. Remember that a NAO charges only when it is powered off and connected to its adapter, and that the pack refuses to charge if it is above roughly 50 °C, so let a warm one cool for 20 minutes first.

I am based in New York and this is a United States–only service. I accept packs from US addresses and ship them back to US addresses. I am not taking international work at the moment — shipping lithium batteries across borders adds customs and dangerous-goods paperwork on both ends that is not practical at this scale. If you are outside the US, there are repairers in Europe who do the same job.

A NAO pack ships by ground only, never air, with the contacts taped, the battery bagged and cushioned in a rigid box, and the box marked with the UN3480 lithium battery mark. At 48.6–62.6 Wh it sits inside the simplest set of carrier rules, so both USPS Ground Advantage and UPS Ground will take it. The shipping section above walks through it step by step, including the exact wording USPS requires on the label and links to both carriers’ official pages.

Send the form first — do not just ship it. USPS prohibits damaged or defective lithium batteries in the mail entirely, and while UPS will carry them by ground within the lower 48 states, it is under stricter packaging rules. A pack that is simply flat and unresponsive is normally fine to send. One that is swollen, cracked, leaking or has been hot needs a conversation first.