In Sena’s defense, at least the battery was easy to remove and replace, unlike the Cardo Packtalk unit I’ll describe next. Unfortunately, the Sena phone tech never mentioned the possibility of a battery failure, and Sena does not offer this simple service. Presumably, they expect me to chuck the old unit and buy a new one.
Cardo and Sena DIY Battery Replacement How-To: Sometimes it's easy, other times it's difficult, but batteries can be changed on these units.
However, you can perform a DIY battery replacement and save what it would cost to replace the whole unit. Some communication devices, such as the Sena SMH10 and the Sena-made Schuberth SC1, have external battery packs. Replacement of an external battery is easy—you don’t need me to explain it to you.
It was replaced by a 3.7V 380mAh 501646 Lithium Polymer battery which was only available from China and came without the correct connector. The construction of Sena SF series, 10S and 50S look similar so it might be easy to open the case and change the battery. I’ve got a little over a year on my 50S with no issues.
Unlike the Sena unit, this battery was hardwired onto the circuit board. The Cardo Packtalk board is very small, covered with surface-mounted components, and the tiny battery wires (about 26 gauge) are soldered on. The replacement is straightforward but not for the faint of heart.
Given the amount of time where these complaints have been present, it doesn't appear that Sena is attempting to address the concerns of its customers, other than by having their customers pay for shipping to have a new unit sent back, that potentially suffers the same issues. Regardless, your question was a fair one and I've reacted accordingly.