As this thread turns into my personal highlights of silly mistakes: Another word of caution for anybody who wants raw battery values sent:
sendBatteryLevel only uses 8-bit: i.e. value from 0-255. Don't try to send your raw 10-bit sensed input from e.g. A0 directly with it.
bool sendBatteryLevel(const uint8_t level, const bool ack = false);
Make sure you divide by 4 or use something like:
int sensorValue = analogRead(ANALOGUE_SENSE_PIN) >> 2;
sendBatteryLevel(sensorValue);
