Hi Steve
Yes, but the e-match fires with much less current before the FET fails...
And those FETS ... They can take short pulses of current far beyond
What they are rated for ...
Anyhow, I thought that may be an issue but I haven't had a problem with the
setup using ematches.
I think the concern is if the ematch fires but somehow the leads get shorted -
I can see that messing things up and maybe even
actually starting a fire!
Thank you
-James
Sent from my iPhone
On Jul 14, 2015, at 7:06 AM, Steve Sawyer <steve@xxxxxxxxxxxxxxxx> wrote:
I agree with Bob, if you want to turn to later technologies, the 2S LiPo is a
very nice small package - just watch out for the FET rating for firing the
pyros. A 180mA LiPo with a 40C rating means that it can deliver 7.2A into a
1 Ohm pyro load (this exceeds the PerfectFlite 5A FET rating).
I've also had discussions with PerfectFlite - they are fairly clear about
recommending the 9V Alkaline batteries (9V NiMH can also be used from Harbor
Freight).
However, I'm using a 3S LiPo (Turnigy nano-tech 180mah 3S ~40C from HobbyKing
or Amazon). This is very small but as I mentioned, requires the added series
resistors on the outputs. The voltage regulator on the PerfectFlite will
allow operation from either a 3S or 2S LiPo.
Steve
From: tccrockets-bounce@xxxxxxxxxxxxx
[mailto:tccrockets-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Feretich
Sent: Monday, July 13, 2015 6:43 PM
To: tccrockets@xxxxxxxxxxxxx
Subject: [tccrockets] Re: battery for stratologger CF
7.4V LiPo (Li-Ion) will work in 95% of all 9V alkaline battery electronics.
The rated voltages are confusing because that 9V alkaline battery advertises
its starting voltage and the 7.4V LiPo battery advertises its discharged
voltage.
Compare the discharge curves...
http://www.feretich.com/Rocketry/Resources/lipotests.html
http://www.feretich.com/Rocketry/Resources/Pdfs/7v%20Li-Po%20vs%209v%20Alkaline.pdf
Assuming your electronics draw 100 mA of current, the cross-over point is at
30 minutes of use. After 30-minutes, the voltage of a 7.4 V LiPo is greater
than a fresh 9V Alkaline.
A fresh (newly manufactured) 9V alkaline battery starts at 9.25V, drops to 9V
after about 7 minutes of use (at 100 mA), and to 7.4V after about 2 hours.
(If the battery has sat on the shelf for a while, it may start at 8.4V.) See
the discharge curve at the provided link. One alkaline battery was freshly
manufactured the other had one month still remaining before its expiration
date.
A fully charged 7.4V LiPo starts at 8.4V and declines slowly to 7.4V. Below
7.4V, the voltage on LiPo (and Li-Ion) batteries drops quickly.
Given that at the end of its rated life, a 9V alkaline battery is only
sourcing 7V, electronics designed correctly to use 9V alkaline batteries will
work fine with 7.4V LiPo batteries.
Regards,
Bob
On 7/13/2015 3:02 PM, Mike Hubble wrote:
Manual says standard 9v is all you need.
On Mon, Jul 13, 2015 at 2:39 PM, Peter Hackett
<peter.hackett@xxxxxxxxxxxxxxxx> wrote:
I've always used a standard 9V alkali battery. Never had any battery problems
with it.
On Mon, Jul 13, 2015 at 2:07 PM, Steve Sawyer <steve@xxxxxxxxxxxxxxxx> wrote:
I've been using 180mah 3S 25~40C Lipos.
For the stratologger CF required protection of the FETs (i.e., short-circuit
or 1 Ohm pyros), I use series 3 Ohm resistors on each output.
Lots of flights are possible.
Steve
From: tccrockets-bounce@xxxxxxxxxxxxx
[mailto:tccrockets-bounce@xxxxxxxxxxxxx] On Behalf Of Ben Sandoval
Sent: Saturday, July 11, 2015 11:01 AM
To: TCC Chat
Subject: [tccrockets] battery for stratologger CF
Which battery are you using for your stratologger cf. I'm getting ready to
order a few batteries and I'm still on the fence. Appreciate your input.
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