The only way the G4 should drain your battery to the point where you couldn't start your car, assuming its hooked up correctly, is if there is something wrong with your battery.
If your battery is old or worn out, the G4 could drain it to a low, but startable level, but the battery could fail to retain its charge for much longer and then go dead. It shouldn't be possible to the G4 to completly "kill" your battery as it will stop drawing power as soon as low voltage is detected. Unlike what leaving the lights on in your car does which is it continues to draw power until the voltage is too low to power anything which is a much lower level then what the G4 will always stop drawing power at and not good for the life of your battery.
There are a number of things you can do to make sure that your battery can support standby without issue.
- Get your battery tested. Pepboys or other auto parts stores will usually test your battery for free and let you know if it needs to be replaced.
- Monitor the G4 closely for its abaility to remain on standby. If the G4 won't make it overnight on standby, its generally a bad sign that your battery needs replacing and if you wait too long before starting it again, you may need a jump.
- Switch the default shutdown method to use hibernate which shouldn't draw any power.
- Use the soft power switch in StreetDeck to shutdown and choose hibernate instead of standby when you are not at home, until you are sure of your battery