Cardo vs Sena

[Grumpy Goat]

...I've never had it notify me of low battery, it just quits working.
Most times it works perfectly.
User error or ......?

I don't think that it is user error exactly. Mine warns me when the battery is getting low (25%?) but if I have music playing it kind of beeps and mumbles the warning so sometimes I miss what is said, although I can usually hear the beep and can guess what it meant. Maybe you are just not hearing it if listening to something else.