Converting a float into two chars

Projects Programming
1

I'm designing a small satellite, and I need to convert the float value of its battery voltage into two chars that I can send via morse code as its telemetry. For example, if the voltage is 4.9034v, I want a 4 and a 9 back. Do I have to convert it to a string first?

I want to limit the amount of memory/processor usage and avoid using large external libraries if possible.

3 
char unitsDigit = '0' + (char)((int)floatVariable % 10);
char tenthsDigit = '0' + (char)((int)(floatVariable*10) % 10);
4

Is there any chance of seeing voltage above 10 volts and, if so, what happens to the fractional component?