The battery does NOT mount inside the helmet.another question.
I read on Throttle buff https://throttlebuff.com/cardo-packtalk-bold-vs-slim/
Your decision may also depend on the type of helmet you going to mount the device on. Also, you need to consider the fact that the Slim doesn’t come with an integrated battery and you will need to mount the battery inside the helmet.
Was it any problem mounting the battery inside the helment?