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Oct 17, 2021, 10:36 AM
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Question

Gas Ignition Battery


What size packs are you all using for your gassers? I am getting back into flying after a number of years and bought a couple used planes with gas ignition, and a couple new engines for builds. I see some rather large packs in the front of some of these planes, and some experienced flyers asking why so big a pack? I am assuming on a larger WWI bird you need the nose weight so why not make it up with something useful? What are you all running?
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Oct 17, 2021, 11:05 AM
Still gassin' it.
I am usually running a single pack for both receiver and ignition, size of course depending on size of plane and anticipated total flighttime per outing.

Small planes (60" ish trainers) can be flown with as little as a single pack 4S NiMH 2000 mAh, larger planed I typically use 4S NiMH 3000~3500 mAh.

But check your ignition for specs, the older types could work on 4,8V, the later types sometimes need a minimum of 6V, which is not a problem unless you do not want your RX and servos to run on 6V, then it is better to have either separate packs or voltage regulators.

Separate packs, your ignition will typically work all afternoon on as little as 1000 mAh.
Oct 17, 2021, 05:01 PM
Registered User
I also run only one battery for both radio and ignition. But as mentioned, you need to check the limits of the ignition module and servos.

In my case, I'm using servos that need to run on LiFe 2 cell batteries (6.6 volts). The ignition modules I have can handle the high volts ( 8.4+ volts). Another consideration is running 2.4 GHz radio. In the old days of 72 MHz you needed to separate the ignition from the radio. But 2.4 GHz is immune to that problem.

For my 2 large gassers (20cc and 50cc), I use 4000 mAh 2 cell LiFe batteries.
Oct 19, 2021, 07:19 PM
Play that funky music right
kenh3497's Avatar
"I am usually running a single pack for both receiver and ignition, size of course depending on size of plane and anticipated total flighttime per outing."


Do you use any kind of opto kill switch ? Plastic pushrod to the carb or metal (cable or solid)I plan in heli ball links for the actual connection to the servo or throttle arm.


I'm putting a RCEXL ignition on a YS 140DZ for what that is worth.



Ken
Oct 19, 2021, 08:16 PM
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Quote:
Originally Posted by kenh3497 View Post
"I am usually running a single pack for both receiver and ignition, size of course depending on size of plane and anticipated total flighttime per outing."


Do you use any kind of opto kill switch ? Plastic pushrod to the carb or metal (cable or solid)I plan in heli ball links for the actual connection to the servo or throttle arm.


I'm putting a RCEXL ignition on a YS 140DZ for what that is worth.



Ken
I always use a RCExl opto kill switch for safety and convenience. One of my gassers has a flexible nyrod pushrod and the other straight metal rod. But both have plastic ball-and-socket links at the engine end.
Oct 20, 2021, 03:09 AM
Still gassin' it.
Quote:
Originally Posted by kenh3497
"I am usually running a single pack for both receiver and ignition, size of course depending on size of plane and anticipated total flighttime per outing."


Do you use any kind of opto kill switch ? Plastic pushrod to the carb or metal (cable or solid)I plan in heli ball links for the actual connection to the servo or throttle arm.


I'm putting a RCEXL ignition on a YS 140DZ for what that is worth.



Ken
Yes, I always use the RcExl opto kill switch. Most modified to feed directly from the receiver busbar, a few still with separate feed, but always a killswitch, never fly without.
Also, never a mechanical switch (regardless of manual or servo operated) because thise can still keep the ignition alive when RX has no power.

An Opto killswitch combined with the proper fail-safe settings will safeguard against 100% of possible runaway situations.

Throttle rods, depend. I have one plane with a metal throttle rod, Z-bend in the carb arm, and it does not create any issues, but usually, I use non-metallic, non-carbon rods and the most accurate links/clevisses availlable. Preferrably ball links to eliminate all play and slop. Not always possible.
Oct 20, 2021, 09:31 AM
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Gary Cee's Avatar
I have always used a separate supply for the receiver. Often use the ignition battery as a reserve supply for the receiver by diode isolating the batteries .(When voltage requirements permit)
Thus allowing the receiver to run from the ignition source and/or the receiver supply. The diode averts the ignition from using the receiver supply.
Latest blog entry: Responsible fliers.
Oct 20, 2021, 09:47 AM
modulate your mixture
i'm sure you're aware (although others may not be) that the diode drops the ignition battery voltage to the receiver by about 0.7v.
Oct 20, 2021, 10:18 AM
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Gary Cee's Avatar
Quote:
Originally Posted by raleighcopter
i'm sure you're aware (although others may not be) that the diode drops the ignition battery voltage to the receiver by about 0.7v.

Yes, I actually count on that as it allows the receiver battery to function as the primary receiver power source.
Latest blog entry: Responsible fliers.
Oct 22, 2021, 03:34 PM
Registered User
Quote:
Originally Posted by Gary Cee
Yes, I actually count on that as it allows the receiver battery to function as the primary receiver power source.
Some years ago, for my first big gasser I used a battery redundancy module. It receives 2 battery inputs and continuously selects the higher voltage source to feed to the Rx. Both inputs dropped by 0.7 volts because of the use of diodes. That unit worked well until one day it got zapped. Thankfully I caught the failure while the plane was on the ground. I never used one again since I was not sure how the module failed.


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