Just wondering if a 5Ah SLA battery would be sufficient for Aerotech G motor ignition. It would be connected to the PSII controller through a JST connector.
I have never tried to fire an Aerotech G motor, but it seems to me that any battery with enough current to set off the igniter for the engine will get the engine ignited. Per the post by
@tokind in this thread, check out the igniter continuity article by J. R. Brohm (2009). Brohm measures the firing current for five different igniters, including the Q2G2 and Copperhead igniters commonly used with composite motors. The Copperhead needs 1.6 amps to fire, so about 2 amps ought to set off the Copperhead very reliably. The Q2G2 takes only about .27 amps to fire, so about 1 amp ought to set it off reliably. If the igniter inserted into your motor is firing reliably, the rocket motor it is inserted into, as long as you have done everything else right, should also ignite reliably. The First Fire Junior igniter required 1.78 amps to set it off.
So, as long as you are igniting only one motor (not a cluster), and as long as you are using the right igniter for the motor, I don't see why the short term current capability of the battery needs to be more than 2 amps. So, a sealed lead acid (SLA) battery with a 2,000 mAh rating ought to be sufficient.
(I am assuming a 12V battery, which should be enough voltage to send a high current pulse through a single igniter.)
NOW, with that said, if you are launching all day, over and over again, rocket after rocket, with no recharge of the battery, and with each launch of a rocket making the battery send at least a 2A current down the wire, you might want a higher amp-hour capacity (say, your 5 Ah battery) for one very good reason: The higher capacity will not go flat as fast and can launch more rockets before needing to be recharged.
Here is a spec sheet for a typical 5Ah SLA battery:
https://batteryguy.com/files/techni...g-1250f1&f2-technical-specification-sheet.pdf
It supposed to be able to sustain a 5 amp output for 30 minutes, ending at a charge of 9.6 volts (flat and needs to be recharged).
That should be plenty of battery capacity for an afternoon of launching from one pad.