Before you start

Installing BAT-BMS is straightforward, but the XAPK format throws a few people off on the first try. Set aside about five minutes and make sure your phone has a steady charge and a bit of free storage. You will also need an internet connection for the one-time install of a helper app.

If you have not grabbed the file yet, it is on the APK page. The rest of this guide assumes it is sitting in your Downloads folder.

Step 1: Get an XAPK installer

Android cannot open an XAPK on its own, so you need a small helper. Open the Play Store and search for "XAPK Installer". Any of the top results works fine — they all do the same job of unpacking the package. Install one, just like any normal app.

You can remove this helper later if you do not want it hanging around. It does not need to stay for BAT-BMS to run.

Step 2: Open the file with the installer

Find bat-bms-1.0.9.xapk in your Downloads. Tap it and Android will ask what app should open it. Pick the XAPK installer you just installed. If your phone does not prompt you, open the installer first and use its built-in file picker to locate the XAPK.

The installer reads the package and shows the app icon and the name BAT-BMS. That is your confirmation that you have the correct file.

Step 3: Allow installs from this source

Because the installer is not the Play Store, Android pauses to ask whether you trust it. This is the "install unknown apps" prompt. Toggle the switch to allow it for the installer only, then tap back. You are not giving blanket permission to anything risky — just to this one helper for this one file.

Why the prompt?

Android protects you from sideloaded malware. Allowing the installer for a single trusted file is normal and safe. You can revoke the permission afterwards in Settings → Apps.

Step 4: Install and open

Tap Install in the installer. A few seconds later you will see the BAT-BMS icon in your app drawer. Open it. On first launch the app asks for Bluetooth and Location permissions — both are needed to find your battery. Grant them, and you are ready for the connection step.

Troubleshooting the install

If the install fails with "app not installed", the usual cause is an older version of the same app blocking it. Uninstall any previous BAT-BMS, then try again. A "parse error" almost always means the XAPK was incomplete — re-download it from the APK page.