Battery 3,6 V for 3-in-1 unit
4004-1
Item numbers 4004 and 4004-1 are both for our 3-in-1 unit, but are compatible with different versions.
4004 is for our older model, whereas 4004-1 is compatible with our newer 2024 model.
You can check the version on the circuit board by unscrewing the four screws on the back.





