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they're about 100mm x 18mm x 12mm, so it's easy to fit them on the back of the sled, and they
have a lot of capacity... about 1200 mAH. You can run all weekend on one charge.
While we're on the subject of 9V alkaline batteries, DO NOT, repeat, DO NOT use a 9V battery
to power the Proton. At all. They don't source much current, especially compared to a 2S LiPo.
While it will appear to work fine once it's new, it will quickly drain, and you will find that the
range starts to rapidly decrease, and the Proton will appear to become unresponsive. If you're
using the single-battery option, the chance of a low-voltage "brownout" is much higher than it
would be with a 2S LiPo. WiFi takes a lot of power, so make sure you feed it well.
In addition, if you are using a single battery we recommend that the current-sourcing capacity of
the battery should be at least 5x the all-fire current of the igniter (or the sum of the igniters, if
you're firing a cluster), to prevent any chance of the voltage dipping. To get that number,
multiply the capacity in mAH by the "C" number of the battery. For example, a 300 mAH
battery rated at 20C will easily put out 6,000 mA, or 6A. If you igniter is rated for 750 mA all-
fire, 5 x 750 = 3750 mA, so that 300 mAH/20C battery would be just fine.
If you're using a separate battery for the deployment side, whatever battery will fire your igniter
or operate your other deployment device (hot wire, servo, etc.) is fine. Little 1S 3.7V 150 mAH
LiPo batteries work great with most ematches, and are so small that you can easily mount them
with a little servo tape just about anywhere you want in your AV bay. The output drivers will
each handle up to 10A and 40V, so if you have something really power-hungry (like a solenoid,
for example), you can simply use a bigger battery. You don't have to worry about "burning out"
the drivers, because they're internally current-limited and thermally-protected; if you try to push
too much current through them, they'll simply shut off until they cool off (kind of like a thermal
circtuit breaker).
You can use a 9V alkaline battery too for the deployment side only with a dual-battery setup
if that's what you like, just be aware that they're pretty big and heavy by contemporary
standards. If you do use a 9V battery, one more thing you need to be careful about is that some
brands of 9V batteries simply have cells pressed together in a metal case, so high G forces can
cause the battery to fail. If you absolutely HAVE to use a 9V battery, we recommend Duracell
9V batteries, because they use welded cells internally and are less likely to come apart than some
other brands. If you do decide to use an alkaline 9V battery, we recommend that you replace it
after EVERY flight. Yes, that can get expensive. And yes, you don't have to worry about your
battery having been drained too much by a previous flight... enough said.
Regardless of what kind of batteries you choose, charge or swap out your batteries before
every session, and check the voltage with a digital voltmeter before every flight. The
voltage check on the Proton is only on the processor battery, it does not test the deployment
battery (assuming it's separate). You don't want to spend all the time to find the "perfect"
battery combination for your 54mm minimum-diameter mach-buster only to realize after you dig
it out of the ground after lawn-staking it that you forgot to charge the deployment battery.
Although you probably won't hurt the Proton itself by dead-shorting the outputs, the voltage drop
due to the short may cause the battery voltage to drop low enough to cause the processor to reset,
although the drivers have a low-voltage cutoff at about 4V that's designed to prevent this from
happening. This is why we recommend having a battery current capacity of at least 5x the all-
fire current of your igniter; if you get a short, chances are that the battery is going to simply
generate a little heat in the drivers and wires for the few seconds that it's on, then it will be
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