Razer Battery Display

Your mouse battery percentage in the tray. No Synapse. No bloat.

A tiny Windows 11 tray app that does one job: it shows the battery percentage of a Razer Viper V4 Pro.

311 KB exe. 1.4 MB of private memory. 1 thread. Effectively zero CPU.

Why This Exists

Razer Synapse wants to run services, background processes, an account login, lighting, profiles, and update prompts, all so you can see one number. If all you want is to know when to charge your mouse, that is a lot of software sitting on a gaming PC doing nothing for you.

So this app keeps the one useful part and throws away the rest. It reads the battery straight from the mouse, shows it in the tray, and gets out of the way. You don't need Synapse installed at all.

What You Get

• The battery percentage right in the tray, as a live number you can read at a glance.
• Green, amber, and red colours, so a low battery stands out.
• The same percentage on hover.
• An automatic refresh every 5 minutes.
• A reading as soon as you touch the mouse. If it was asleep at boot, the first movement picks it up.
• Left-click to refresh on demand.
• One-click updates from the tray menu.
• Starts with Windows, and you can turn that off from the tray menu.
• A normal per-user install with a normal Apps & Features uninstall entry.

What You Don't Get

Razer Synapse	Razer Battery Display
Background services	None
Account login	None
Telemetry and online features	None. It only goes online when you click Check for Updates
Lighting and profile engine	None
Update prompts	None. You check when you want to
Large install	One 311 KB exe

How Light Is It?

Measured on Windows 11 with the release build installed:

Metric	Result
Exe size	311 KB
Private memory	about 1.4 MB
Working set after the first reading	about 0.4 MB
CPU time in the first minute	about 0.02 s
Settled threads	1
Handles	about 133
Services installed	0
Background network connections	0

The working set grows back a little with use, and most of it is shared Windows DLL memory.

That number is the result of deliberate choices, not just using Rust:

• Native Win32. No webview, no runtime, no framework, and one dependency: Microsoft's Windows API bindings.
• Asleep until needed. The app waits on the Windows message loop and uses no CPU between refreshes. There is no busy loop.
• Direct driver requests. Battery reads go straight to the HID driver, so hid.dll and setupapi.dll are never loaded.
• Built-in pixel font. Tray digits are drawn from a tiny font inside the exe, so no font or text-shaping libraries load. The icon is only redrawn when the percentage changes.
• Efficiency mode. The app asks Windows to schedule it as a low-power process and lets its timer share wake-ups with other work.
• Startup memory handed back. After the first reading, memory used only during startup is returned to Windows.

Safe While Gaming

The app never hooks your mouse and never reads pointer data. It only talks to the Viper V4 Pro's non-pointer HID feature interfaces (mi_03 and mi_04), then caches the working path. It never sends feature reports to the mouse or keyboard input collections.

If Windows starts the app before the mouse is ready, it retries after 10, 20, 30, and 60 seconds. While it has no battery value, it also registers for a single Windows Raw Input notification. The first movement removes that registration straight away, so the app never receives a stream of mouse events, even at 8000 Hz. It reads the battery 750 ms later, which gives a sleeping mouse time to reconnect, and the contents of the event are ignored.

If that read fails, the listener stays off for 15 seconds, so using a different mouse can't cause constant reads. The first good read removes the listener and returns to the normal 5-minute refresh.

Updating

Right-click the tray icon and choose Check for Updates. If a newer version is out, say yes and the app downloads it, verifies its SHA-256 checksum, installs it, and restarts itself.

Nothing checks in the background. The update check runs in a short-lived separate process using the curl built into Windows, so the tray app itself carries no network code and stays offline.

Supported Mouse

• Razer Viper V4 Pro wired: 1532:00E5
• Razer Viper V4 Pro wireless: 1532:00E6

The battery query follows the same command path as current OpenRazer Viper V4 Pro support work. Windows does not expose this mouse's battery through the normal device battery property, so the app reads the Razer HID battery report directly.

Install

Download RazerBatteryDisplaySetup.exe from Releases and run it. It installs for the current user, starts the tray app, and enables startup with Windows.

To build the setup exe yourself:

cargo build --release
New-Item -ItemType Directory -Force dist
Copy-Item target\release\razer-battery-display.exe dist\RazerBatteryDisplaySetup.exe -Force
dist\RazerBatteryDisplaySetup.exe

For a quiet reinstall from a fresh build:

target\release\razer-battery-display.exe --install-quiet

Tray Menu

Left-click refreshes the percentage. Right-click for:

• Refresh
• Start with Windows
• Check for Updates
• Uninstall
• Quit

Build Checks

cargo fmt --check
cargo clippy --all-targets --all-features --locked -- -D warnings
cargo test --all-targets --all-features --locked
cargo build --release --locked

Hardware probe:

cargo run -- --probe

Verbose probe with full HID instance paths:

cargo run -- --probe-verbose

Privacy

The app only talks to the local HID device and the current-user Windows registry entries needed for install, startup, and uninstall. Startup uses the normal per-user Run entry, not a service or scheduled task. The only network request is the one you start with Check for Updates, which talks to this project's GitHub releases. It collects no telemetry and stores no personal data.

License

MIT. Not affiliated with or endorsed by Razer.