User`s manual

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possibly a whole flying weekend. You CAN use a battery as small as 200 mAH if you have a
small rocket and know that it’s not going to be “on” for more than 2 hours; we’ve done that with
rockets using 24mm and 29mm motors, but you have to recognize the limitations, and make sure
you charge it before every flight (which you should do anyway!)
We do NOT recommend using a 9V alkaline battery to power the Eggfinder GPS. The
Eggfinder GPS draws too much current, and you will find that your battery is only going to last
for 2 hours, if that. A 350 mah 2S 7.4v LiPo is about the same size and weight, and can source
much more current for much longer.
For deployment power, your battery is largely going to be dictated by the requirements of your
deployment igniter. Most igniters that are commonly used for deployment initiation nowadays
use relatively low current, well under 1A “all-fire” (the guaranteed minimum current
requirement for firing). Quest Q2G2’s will fire at under 200 mA. Typically, a very small LiPo
is more than adequate for deployment power, a 200 mAH battery will easily light any igniter up
to about 4A, and depending on the battery might be able to source up to 8A. Since igniters fire
for only a short time and typically will burn open after firing, that current may only be drawn for
a few tenths of a second. You generally CAN use a 9V battery for the deployment side,
assuming that it will put out enough current for your igniter. (It will work fine with a Q2G2).
IF AND ONLY IF you are using Quest Q2G2 igniters or other low-current igniters, you can get
away with using a single battery for both the computer and deployment side. We’ve done that
many times, it works fine if you make sure that your battery is large enough to handle a possible
short. We recommend that your LiPo battery has enough current capacity to handle 10x the all-
fire draw of the igniter. For example, if you are using a J-Tek ematch with a 1A all-fire rating,
your battery must be able to handle 10A of current continuously. To tell if your battery can
handle that, look at the “C” rating of the battery, and multiply the capacity by the C-rating. The
C-rating tells you how much current the battery can put out continuously; the higher the rating,
the more current the battery can source. If you have a 500 mAH battery rated at 20C, that’s
10,000 mA or 10A, so it would be OK to use that battery with a J-Tek match as the sole battery
on an Eggtimer TRS.
General Battery Procedures
TEST YOUR BATTERY WITH A DVM BEFORE EVERY FLIGHT!!!
If you do not have one, buy an inexpensive digital voltmeter and check the battery voltage while
the Eggtimer is powered ON, before EVERY flight. Your battery should be at least 80% of its
rated voltage; if you are using LiPo batteries, you should never let your battery go below 3.1v
per cell, i.e. a 2S LiPo should never go below 6.2V. If your battery reads below this, chances
are good that it is damaged and will not retain a charge.
Similarly, test the deployment batteries as well if you are using electronic deployment. Check
your igniter vendor’s guidelines for recommended voltage, and replace the battery if it’s close to
the minimum value, or if the voltage is less than 80% of its rated value, whichever is highest.
For example, a Quest Q2G2 igniter will fire with as little as 3.7v (a fully-charged LiPo cell), but