This was a quick test to see how much current at what voltage would be required to fire an igniter made from 40
gauge nichrome wire. I attached the nichrome wire between two copper wire strands .57" apart. Each battery
or pack of batteries were tested for open circuit voltage, then tested for short circuit amps.
When each battery/pack was connected to the nichrome wire, I recorded the amps that were drawn and the battery voltage under the load.
The nicad batteries were fairly new and fully charged, but not the greatest quality. The 9 volt transistor battery was used. The lithium battery was a new high capacity lithium thionyl chloride cell.
| Battery | Open Voltage | Short Circuit Amps | Current Draw | Volts at Draw | Watts | nichrome Wire Condition |
| 1) AA NiCad | 1.31 | 3.08 | .11 | 1.25 | .1375 | No Change |
| 2) AA NiCads | 2.63 | 5.11 | .38 | 2.34 | .8892 | No Change |
| 4) AA NiCads | 5.16 | 7.21 | .65 | 4.60 | 2.99 | Dark to Bright Red, Very Slight Delay |
| 9 volt Battery | 8.2 | 2.3 | .7 | 5.32 | 3.724 | Bright Red Instantly |
| 8) AA NiCads | 10.41 | 9.31 | ? | ? | ? | Burned wire too fast to record data. |
| 1) Lithium | 3.68 | 2.36 | .46 | 3.59 | 1.651 | Wired heated to blackened state, no glow. |
The results for the most part weren't a big surprise. Neither a single, or two AA batteries in series provided enough power to get the nichrome wire to glow red, the single lithium battery failed as well. 4 AA NiCads in series would seem to be about the minimum, while the 9 volt battery continues to be a good choice, and the pack of 8 AA NiCads in series are almost overkill.
What it boils down to is this. Amps alone won't do trick, nor would voltage alone. You could have a source of power that supplied 100 amps, but if there wasn't enough voltage to push the electrons through the wire, it won't light an e-match. Or you could have 100 volts, but if there isn't enough amps (flow), the e-match won't fire. I have heard people talk of amps lighting an e-match, they say you need X number of amps and that's all there is to it. But amps don't do work, Watts do work, or at least are a measure of work. Amps x Volts = Watts, you need both.
One thing I did find interesting. When you take 2 batteries and hook them up in series, the voltage should double, while the amps stay the same. If you put the same 2 batteries in parallel, the volts should stay the same and the amps double. In my tests I increased the battery count by hooking them up in series, and the voltage pretty much doubled each time I doubled the number of batteries. But look at the amps, the amps went up significantly as I added batteries. From 1 AA to 2 AA's the amps increased 66%. From 2 AA's to 4 AA's the amps increased 39%. And from 4 AA's to 8 AA's the amps increased 29%. I'm sure that's due to wiring resistance, and the very small diameter wires in my meter leads, but it's more than I expected to see.
In summary, a battery pack of six volts with sufficient current flow is about the minimum to light a homemade e-match. That's just the e-match and not the flight electronics. A fresh 9 volt alkaline transistor battery can source between 5 and 6 amps for a short time, but the current goes down quickly with use. A pack of 6 NiCads would seem to be about perfect for deployment purposes.