[BSDfan666]

Let's try that again...

#include <stdio.h>
#include <sys/types.h>
#include <sys/sysctl.h>

int main(void) {
	int mib[4], life;
	size_t miblen, lifelen;

	miblen = sizeof(mib);
	lifelen = sizeof(life);

	if(sysctlnametomib("hw.acpi.battery.life", mib, &miblen) == -1) {
		return 1;
	}

	if(sysctl(mib, miblen, &life, &lifelen, NULL, 0) == -1) {
		return 1;
	}
	
	printf("%d\n", life);
	
	return 0;
}

Hope it helps..