Hi,

I bought this one at AliExpress for my TomTom Runner 2 Cardio and the battery totally fits but, be aware, the polarity is inverted. I had to pay an electronics technician to change the battery wiring. The connection plug is not symmetrical, which means that turning the wire isn’t enough, you need to change the connector.

Overall, it’s still a good deal, since I love this watch and payed around €22 for the battery and the technician.

I’ll post again once I charge the battery and evaluate how long it’ll run.