For Alta HR owners:

Hi, i’ve successfully repaired my Alta HR with this tutorial, even if it is actually intended for a normal Fitbit Alta.

The procedure is the same excepted the order of the steps 3 to 6.

At step 3, before unscrewing the 2x torx 2 screws, (Alta HR has 2 screws instead of one) let them in place.

1/ Unsold the 2 contacts with the red and black wire.

Otherwise you gonna get blocked for pulling the battery out because of the sensor ribbon connected in the middle of the MB.

2/ Unscrew the torx screws

3/ Replace the battery (only 7€ for me in 2021)

4/ Screw the two screws back to the MB.

5/ Resold the contacts and the wires: black on -, red on + (basically step 6)

Follow step 7.

IMO it’s easier to do it this way for the Alta HR because of this new ribbon. But the whole procedure is basically the same.