10-01-2018 07:25 AM
Welcome to the Community Forums.
If you are referring to the RTC (real time clock) battery, then it is on the underside as shown in the image below:
I hope this helps answer your query.
10-01-2018 05:45 PM
10-02-2018 08:07 AM
Welcome to the Lenovo Community dika_widiyanto !
In addition to the information Spidey101 provided it would appear, from the image posted, that the RTC battery on your model is soldered directly to the motherboard. It's removal or replacement will take some soldering skills when working with batteries to safely remove it. If you are not comfortable in removing the battery then it is best if you seek out a service center to do this for you.