Hello again,
[1]
I fear you did not understand me correctly or i didnt explain the relationship between the physical positioning of the primary and secondary so let me try to expound that a little more first.
Originally you had shown a drawing where the primary turns were wound on one side of the core and the secondary was wound on the other side of the core, so that the two windings never touched at all. This means the two windings did not overlap at all in any area, but more basically that means that there was separation distance ALONG THE CORE DIAMETER, or to put it another way, the two cores were placed in entirely different sectors of the toroid. The distance between windings along the core diameter is the most important distance, more so than the distance between vertical distance between windings when they are wound one on top of the other. So it was never a question of if the primary went on TOP of the secondary or the secondary went on TOP of the primary, it was only a question of if the two windings overlapped, and thus making the distance between winding (along the diameter) zero or very small and thus they are wound in the same sectors and actually take up the whole diameter, both of them. There may be a small advantage to placing the secondary right on the core and primary wound over that, but in this low power design it probably wont matter much.
You'll notice that in physical inductor equations the length is in the denominator, so as the length increases the inductance goes down. That length is the "magnetic path" length and so windings that are actually separated ALONG THE LENGTH of the magnetic path will have less coupling than those that are not.
[2]
It sounds like your main problem is the drive method. You should probably look into the line of transistors made by Zetex (Diodes Inc) if you want to use bipolars for a low voltage application like this.
[3]
Your run time target goal does not seem reasonable, sorry to say. That is because of the limited energy available from a single AA cell. Even an alkaline may only be able to put out 2 amps for 1 hour at most, and assuming the voltage did not fall (which it really does) the max energy output would be 2*1.5=3 watt hours, which means even with perfect components and really ideal battery you would only see 1 hour of run time. This means you need to change something drastically if you want 4 hours run time. Also sorry to say, but the ONLY way to improve this is to add more batteries or a bigger battery or a different type of battery which would be bigger also.
[4]
Not sure how you are measuring this. If you have the cap across the input of the board and your meter external to that, it should work.
Summary:
1. Wind primary and secondary one on top of the other.
2. Look for bipolars made by Zetex.
3. Use bigger battery or more batteries.
4. Draw picture of your measuring set up and post here.
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