Lipo ??

[ThreeJsDad]

How many ignites do you folks think I can do with a 3S 850mah battery if i am flying with Estes igniters and no clusters, all LPR's.

 

[Tobor]

Public Missiles Igniters White Paper by G-Wiz (Link)
Apogee Rockets Igniter Report (Link)

 

[Speaknoevil]

Say you source 1A for 0.2S per flight. That is 200maS per flight. Your capacity is 850maH as stated. So you have:
850maH/200maS/flight*3600S/H=15,300 flights.
The thing I don't know is the C rating of your battery. There is some relationship to the C rating of a LiPo and the current sourcing as it reaches it's low voltage limit.

 

[ThreeJsDad]

Public Missiles Igniters White Paper by G-Wiz (Link)
Apogee Rockets Igniter Report (Link)

Those papers presume I understand all of this..... I guess I will make sure I have extra batteries.

 

[ThreeJsDad]

Say you source 1A for 0.2S per flight. That is 200maS per flight. Your capacity is 850maH as stated. So you have:
850maH/200maS/flight*3600S/H=15,300 flights.

Thanks Bud, basic math I can follow....LOL

 

[Tobor]

C = Max constant current discharge rate. So a 25C pack can pump out 25A without killing itself.

 

[BEC]

As a practical matter, the continuity and arming indication (lamp/LED/buzzer/whatever) will play into this.

I will say this: I have a 3s 1250 mAh pack in my Estes PSII controller and I can fly a whole season without charging it, and this includes using it for composite motors, not just using Estes igniters/starters.

C = Max constant current discharge rate. So a 25C pack can pump out 25A without killing itself.

Actually, a 25C pack can (if the rating is honest) deliver 25x the capacity number of the pack.Or to look at it another way, you can safely discharge the pack in 60/25 minutes - 2.4 minutes.

In the case of the OP's 850 mAh example, 25C would be 21.25A. That also, of course, depends on the rest of the circuit/load.

 

[Tobor]

Actually, a 25C pack can (if the rating is honest) deliver 25x the capacity number of the pack.Or to look at it another way, you can safely discharge the pack in 60/25 minutes - 2.4 minutes.

In the case of the OP's 850 mAh example, 25C would be 21.25A. That also, of course, depends on the rest of the circuit/load.

Yeppers, I stand corrected. I have 2 1000mAh packs and was thinking in terms of those packs. Ooops....

 

[ThreeJsDad]

As a practical matter, the continuity and arming indication (lamp/LED/buzzer/whatever) will play into this.

I will say this: I have a 3s 1250 mAh pack in my Estes PSII controller and I can fly a whole season without charging it, and this includes using it for composite motors, not just using Estes igniters/starters.


Actually, a 25C pack can (if the rating is honest) deliver 25x the capacity number of the pack.Or to look at it another way, you can safely discharge the pack in 60/25 minutes - 2.4 minutes.

In the case of the OP's 850 mAh example, 25C would be 21.25A. That also, of course, depends on the rest of the circuit/load.

I was hoping you would comment because I thought I remember you posting something along these lines previously. Thank You !

 

[BEC]

Yeppers, I stand corrected. I have 2 1000mAh packs and was thinking in terms of those packs. Ooops....

That would do it....

 

[DaveW6DPS]

Those papers presume I understand all of this..... I guess I will make sure I have extra batteries.

If you don't understand the science and math involved, do it the old fashioned way. Get a bucket of igniters and start testing. Or start launching and see how it goes.

Yes, spare batteries are always a good idea. Also a way to recharge at the launch can help.

 

[KilroySmith]

How many ignites do you folks think I can do with a 3S 850mah battery .

As many as you have. As The Kinks sang, it'll last "All day, and all of the night..."

 

[caveduck]

As a real world data point, DART gets ~1000 launches on ~50% of a 2200 mAh 3S LiPo. Our system has 2 15-20 ma indicator LEDs that are on nearly continuously, and they probably account for 2/3 of the current drain. So I'd expect that with an 800 mAh class battery with much less continuous drain you'd still get close to 1000 launches.