2015, Mercedes GLA 250 auxiliary battery DIY 

Replacing the Auxiliary battery in a 2015 GLA250
It is located in the passenger front footwell

[@Elektrodrell]

thanks for the video. just a side note on order of operations :) be sure to always disconnect negative (-) terminal first - your entire car chassis is a negative terminal and if you start with positive and touch chassis with a tool - you can short it, potentially damaging electronics, producing sparks etc connecting terminals back is reverse: positve first, negative second

[@schehl614]

*** Remove the cabin air filter door to get hinge of the battery cover far enough to open; don't just break the hinge on the battery door. Good time to replace the cabin filter also.

[@EvangelistKia]

Ok friend did you disconnect the main battery first?

[@lizann5549]

No

[@PeterSchneemann]

why are there two?

[@miklmiklmtrcycl6009]

It keeps electronics working - stored codes etc-when the main is dead or disconnected

[@oldiam]

and now, let the rattling noise begging because you did not put the battery cover properly in the hinges. What a butchering job. But, thanks for showing the wrong way of doing it. I learned more than if it had been perfect.