user 30299
L2 - NAR & TRA
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Every so often there are posts about the use & qualities of 9-volt batteries for rocket electronics.
I thought it would be interesting to grab a handful of 9-volt batteries and test their volts and
amps over several months.
Below are some pictures from the testing. I chose 11 batteries. I used two multimeters so that
I could watch voltage on one, and used another meter to “short” the battery and read the amps.
The last step in all this work was for me to tear apart each battery, take pictures, and see how
they were constructed.
It’s not super scientific. I did not have a data logger to collect the voltages and amps through
a test cycle. I read the numbers straight off the displays. What I did was read the voltage before
shorting the battery. I would short the battery for 2 seconds, then wait 15 seconds to short the
battery again for another 2 seconds.
I stripped the jacket off the 9-volt clip so that I could short the battery through the top contacts
with one multimeter, and at the same time read the volts with the other multimeter.
I read the amps after the 1st 2-second short, then read the volts at the end of the 15-second
“recovery”, and then read the amps after the 2nd 2-second short. I did this over a number
of months. I started back in May. Sometimes it was a few days between each test cycle,
sometimes it was a week, and sometimes a couple of weeks. It was irregular, just like what
we experience between launch dates and events. Each battery was tested 14 times between
May and December.
The two shortening events were to represent a dual-deployment launch for the firing of
two e-matches. Most fight controllers appear to use a 1 second count for firing (shorting)
the e-matches. I used 2 so as to make sure I put the battery through a solid shorting.
The 15-second recovery was not an arbitrary number. I looked at the flight simulations,
and actual flights, on some of my dual-deploy rockets and picked a happy medium.
This time period will vary greatly depending on a person’s rocket and launch conditions.
But hey, you have to start somewhere . . .
I thought I would start with some pictures of the batteries and what they look like inside.
Some have the nice (6) cell arrangement with welded connections. They always had the
highest amp readings; 4 to 5 amps. Four batteries are in this class.
Then there were the ones with a flat stack design, and a solid, clear plastic shell. Their amp
readings tended to run between 2 and 2.5. I have not cracked open a shell yet to see how
the top and bottom plates are anchored. The plastic shells looked to be very durable.
Five batteries are in this class.
Then there were two batteries that barely put out 0.75 to 1.0 amps. Look for the pictures
of the No. 5 and No. 7 battery. I will let you use your imagination as to what you think is
actually wrapped in the plastic wrap. Yup, no solid shell - just plastic wrap.
I plan on a Part 2 for this which will have some graphs showing how each battery's volts
and amps performed over time. It may be a week or two before I get that posted.
This exercise was not meant to create a definitive answer on the use & qualities of 9-volt
batteries. I did it because of shear curiosity. There are probably a hundred other ways to
test the batteries, and some may do a better job of replicating what we put these batteries
through in our rockets. I had fun, and I learned some neat things about 9-volts.
Pictures for Battery No. 6 thru No. 11 are in a second thread.
I thought it would be interesting to grab a handful of 9-volt batteries and test their volts and
amps over several months.
Below are some pictures from the testing. I chose 11 batteries. I used two multimeters so that
I could watch voltage on one, and used another meter to “short” the battery and read the amps.
The last step in all this work was for me to tear apart each battery, take pictures, and see how
they were constructed.
It’s not super scientific. I did not have a data logger to collect the voltages and amps through
a test cycle. I read the numbers straight off the displays. What I did was read the voltage before
shorting the battery. I would short the battery for 2 seconds, then wait 15 seconds to short the
battery again for another 2 seconds.
I stripped the jacket off the 9-volt clip so that I could short the battery through the top contacts
with one multimeter, and at the same time read the volts with the other multimeter.
I read the amps after the 1st 2-second short, then read the volts at the end of the 15-second
“recovery”, and then read the amps after the 2nd 2-second short. I did this over a number
of months. I started back in May. Sometimes it was a few days between each test cycle,
sometimes it was a week, and sometimes a couple of weeks. It was irregular, just like what
we experience between launch dates and events. Each battery was tested 14 times between
May and December.
The two shortening events were to represent a dual-deployment launch for the firing of
two e-matches. Most fight controllers appear to use a 1 second count for firing (shorting)
the e-matches. I used 2 so as to make sure I put the battery through a solid shorting.
The 15-second recovery was not an arbitrary number. I looked at the flight simulations,
and actual flights, on some of my dual-deploy rockets and picked a happy medium.
This time period will vary greatly depending on a person’s rocket and launch conditions.
But hey, you have to start somewhere . . .
I thought I would start with some pictures of the batteries and what they look like inside.
Some have the nice (6) cell arrangement with welded connections. They always had the
highest amp readings; 4 to 5 amps. Four batteries are in this class.
Then there were the ones with a flat stack design, and a solid, clear plastic shell. Their amp
readings tended to run between 2 and 2.5. I have not cracked open a shell yet to see how
the top and bottom plates are anchored. The plastic shells looked to be very durable.
Five batteries are in this class.
Then there were two batteries that barely put out 0.75 to 1.0 amps. Look for the pictures
of the No. 5 and No. 7 battery. I will let you use your imagination as to what you think is
actually wrapped in the plastic wrap. Yup, no solid shell - just plastic wrap.
I plan on a Part 2 for this which will have some graphs showing how each battery's volts
and amps performed over time. It may be a week or two before I get that posted.
This exercise was not meant to create a definitive answer on the use & qualities of 9-volt
batteries. I did it because of shear curiosity. There are probably a hundred other ways to
test the batteries, and some may do a better job of replicating what we put these batteries
through in our rockets. I had fun, and I learned some neat things about 9-volts.
Pictures for Battery No. 6 thru No. 11 are in a second thread.