If you are using an Estes 'Solar' igniter you can pop it with four AA batteries in series. That is 1.5V each for a total of 6V.
Quest ignitors seem to take a little more. I have not used many of them (I use Estes igniters on the Quest motors) so I am not sure, but I think someone here on TRF said to use at least 9V, preferably 12V.