ADCIN 4, adval 'Read channel 4 to adval
adval1 = adval*2/100
adval2 = adval*4//10
Lcdout "POWER: ", DEC2 adval1, ".", DEC1 adval2," WATT "
I don't think that's what you want.

Let's say that you have 4.8 V on the input. You'll get an A/D reading of 249.

249 * 2 / 100 = 4   This part is ok
249 * 4 = 996, and //10 gives 6
So that would display as 4.6 instead of 4.8

Or if you had 4.2 V, (214 A/D)

214 * 2 / 10 = 4   Still OK
214 * 4 = 856, and //10 gives 6
Still displays as 4.6 instead of 4.2

Here are some more results
Code:
Volts	A/D	Whole#	4*A/D	//10	Result
5.00	255	5	1020	0	5.0
4.90	249	4	996	6	4.6
4.85	247	4	988	8	4.8
4.80	244	4	976	6	4.6
4.75	242	4	968	8	4.8
4.70	239	4	956	6	4.6
4.65	237	4	948	8	4.8
4.60	234	4	936	6	4.6
4.55	232	4	928	8	4.8
4.50	229	4	916	6	4.6
4.40	224	4	896	6	4.6
4.30	219	4	876	6	4.6
4.20	214	4	856	6	4.6
I think you should take another look at the formulas in post #9