I have a foc.us tDCS headset that was becoming unusable due to a failing battery. I decided to replace the battery myself rather that take the time and effort to return it to foc.us for repair. I thought you might want to see what is involved in battery replacement. It’s not a job for a novice – good soldering skill (and good vision) is required. If you don’t want to tackle the job yourself, a local battery replacement shop might be able to do it as they often do soldering work.
The battery in the foc.us headset is a small 3.7V, 150 mAh lithium polymer type (model 041230) and like any battery is prone to eventually fail. It is available from a number of sources – including EBay where I purchased mine for $3. By the way a single AA alkaline battery has a capacity of about 2,000 mAh – thus explaining the need to charge the foc.us headset fairly often.
To replace the battery, you must remove the back cover which is held in place by two small torx-style screws. If you don’t have a small torx drive around, you may find a small flat-blade screwdriver will suffice. Once the screws are removed, gently bend the headband back and the cover can be lifted away. Inside you will find a small circuit board, the lithium polymer battery, and very thin, delicate wires. Use great care as you work to avoid breaking a wire.
You will need to gently lift the board off of the plastic pins that position it as the solder connections for the battery are on the underside of the board. You can then turn the board over for desoldering the old battery and soldering the new battery in place.
(With the cover removed, the battery, circuit board, and thin connecting wires can be seen.)
(I use a “third hand” to hold the board while I do soldering work. Note the red, positive battery lead is to the outside edge of the board.)
Once the new battery is soldered in place, you can return the circuit board to its alignment posts, place the battery on top of the circuit board, and then put the cover back in place. Be careful not to crimp the fine wires from the battery or those running to the electrode sockets. Once the cover is back on, reinsert and tighten the two torx screws and you are done!
I suggest you give the headset a good two or three hour charge and it should be ready to go.