14500 subbed for AA?

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dhbarr

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I notice a lot of rocket and pyro remote systems like 4xAA's, but I've had some trouble with different kind of igniters.

It seems fairly straightforward to drop in 900mAH 14500 rechargeables instead ; I was wondering if anybody had success ( or horror ) stories doing this?

Last launch I just wired a car battery directly to the guts of my Estes controller, would rather not do that a bunch more times.
 
The Estes controllers that use a 9v battery can easily be swapped to using a 3s lifepo4 battery from hobbyking. They have a nominal voltage of 9.9v and supply a nice amount of juice for most igniters. You might find that a single 14500 won't have enough voltage for some igniters.
 
I have used rechargeable AA's once mine. Worked fine, but then my Son wanted them back for his X-box controller.
I only did six flights that day, so I know they are good for atleast that.
 
The Estes controllers that use a 9v battery can easily be swapped to using a 3s lifepo4 battery from hobbyking. They have a nominal voltage of 9.9v and supply a nice amount of juice for most igniters. You might find that a single 14500 won't have enough voltage for some igniters.
I have the Estes E controller., which uses 4x AA = 6V , was thinking about dropping in 4x 14500 = 14.8V . I know the mAH will drop drastically, but I'm planning on replacing the lamp with an LED anyway.

Which Estes ( or other manuf. ) controllers use a 9v by default?
 
If you are planning to use 4, you could wire them series parallel giving you 7.4v and double the mAh and you should be good. The Astron II controller uses a 9v battery.
 
I have the Estes E controller., which uses 4x AA = 6V , was thinking about dropping in 4x 14500 = 14.8V . I know the mAH will drop drastically, but I'm planning on replacing the lamp with an LED anyway.

I ran this test today without the lamp<->LED swap ( soon though ). I can report good initial results, 0.24mA @ ~14V on continuity check, 16+V on fire.

Should be sending up a few 1/2A and A10's tomorrow at the Scout-O-Rama together with Tulsa Tripoli, will report back if I have better luck than last time with the Estes Starters.
 
14500 is a battery size, not a battery chemistry. An alkaline battery has a nominal voltage = 1.5 volts. A NiCad or NiMH battery has a nominal voltage = 1.2 volts. A LiPo battery has a nominal voltage = 3.6 volts, and a LFP battery has a nominal voltage =3.3 volts.

A system designed to operate with 4 AA batteries is designed to operate at 6 volts. 5 AA NiCad or NiMH batteries is an equivalent match, but most systems designed to run on 6 volts will operate at 4.8 volts which is what you get with 4 AA NiMH or NiCad batteries. 2 AA Li batteries are the closest equivalent to 4 Alkaline AA batteries producing either a nominal 7.2 volts or 6.6 volts. When using Li batteries, a load will attempt to draw a higher current in proportion to the voltage ratio or 7.2/6.0 = 120% which is 20% higher than with the alkaline batteries, or 6.6/6.0 = 110% or 10% higher with LFP batteries. If you use 4 batteries, the load will attempt to draw more than twice the design current because the supply current is more than twice the design current. (It's simply ohm's law, I=V/R, in practice.) The power drawn by the load is proportional to the current squared, so the power draw using 4 Li batteries is 4 times that of the alkaline batteries.

If the battery has a low enough impedance so it can supply the current draw required by the lot without difficulty, the battery will be happy. If the current and power delivered due to the higher voltage simply causes an igniter to active quicker, that's also good. But if the current is high enough to over heat the wiring, or burn out a lamp filament or LED, than it's not good.

The bottom line is you should do some very simple specification checks and ohm's law calculations before you change the battery chemistry.

Bob
 
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