John
From what I gather, Perfectflite did current measurements for the Sanyo battery and present the test results on page 11 of the timer manual. I performed a sanity check to his numbers by simply using the internal resistance of the battery as measured at 1000 Hz in the Sanyo data sheet to determine the short circuit current delivered for a millesecond.
R = .210 ohms, V ~ 8 volts, I = V/R = 8/.21=38 amps for 1 msec.
You can't pull that much current for a second due to diffusion limitations and other physical chemical phenomenon within the battery. (I won't go into details here, because it 's pretty high level chemistry.) (To add to the confusion, the Sayno data sheet use "lt" as the 1 hour rate current instead of the "C" (Capacity in AH) that is found in the American data sheets.)
The point I was trying to make (which was also pointed out by Steve) was that you have to pick out the right battery to fire high current ignitors. It's the current, not the voltage that fires an ignitor, and the internal resistance (impedence) of the battery is the determining factor. (The voltage is simply the force required to push the current through the circuit.)
For a given A-H capacity, a battery with a low internal resistance can deliver higher currents for shorter periods of time than a same capacity battery with a higher internal resistance.
Modern NiCad and NiMH batteries in a "9 volt transistor battery case" are made from either 6, 7 or 8 individual batteries connected in series rated at 7.2, 8.4 and 9.6 volts respectively.
Most 7.2 volt versions are made by packaging 6 1.2 volt cylinderical "AAAA" cells in the case. The cells have a large electrode area and therefore have a low internal resistance and are designed to deliver a lot of current in a short period of time. The 8.4 volt versions are typically 7 "pancake" cells with a relatively small electrode area (higher resistance) which is good for supplying lesser currents for longer periods of time. (The 9.6 volt versions are relatively new and I don't know much about them but are most likely "pancake" construction.)
Only the 7.2 volt versions can deliver the currents required to fire ignitors promptly.
What most folks don't know is that the most rapid ignition of an ignitor occurs when the resistance of the timer circuit is equal to that of the ignitor. That because the maximum possible power is being delivered to the ignitor so it heats up in the shortest possible time. I have attached a graph of the power delivered to an ignitor as a percentage of it's resistance in the firing circuit. For example if the ignitor has a resistance of 1 ohm, optimum igintion speed occurs when the resistance of the battery, firing circuit, and wires equals 1 ohm, but anything less is ok because that means you get higher current than required but it is way about the minimum all-fire current. If the circuit resistance is greater than that of the ignitor, you might not be able to deliver the minimum all fire current if the battery is not fresh.
Most ignitors are not well characterized, but DaveyFire had some great info that is no longer posed. For their e-matches, a current 3x larger than their all-fire rating usually resulted in a sub-millesecond ignition delay.
Hope this is not too confusing.
Bob Krech
