Mommy's golfcart doesn't have a usable fuel gauge (battery level meter), or a clock. I have fixed that.
I slapped an Adafruit OLED (same as on my skateboard) onto a Particle Photon. I used a simple voltage divider to split the ~56v battery string down to something measurable, and a 48V relay to turn on/off a lower-voltage (~18V) line to power the voltage regulator.
The Photon awesomely has a very simple battery backup connection (so there's a lithium battery in there too), and the clock awesomely syncs up whenever it finds the cloud.
The display currently shows a fuel gauge bar, under that it has raw ADC value (debugging), a calculated voltage level, and a symbol showing the device's state of connectivity -- z (sleeping), + (connecting), * (connected). The device doesn't like being disconnected generally, so I detect that state and disconnect manually. It will reconnect on power-up, or if it senses the cart being charged (e.g. in my garage).
The clock display uses the built-in font, has a blinking cursor (currently "off"), and a smaller seconds display (also for debugging).