New Tripoli Unified Safety Code

LithosphereRocketry

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And you have magical batteries that last for days or weeks which would cause the above to be an issue? Please provide links here, as I'm interested in this magical tech you EEs have access to that us mere mortals don't.
Here's a link:

A fresh 9V battery has a capacity of 550 mAh. An RRC3 draws about 6mA of current at idle. That works out to about 4 days of continuous operation. Useful life is probably less than that, but I wouldn't want to push limits when pyrotechnics are involved.
 

FredA

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A fresh 9V battery has a capacity of 550 mAh. An RRC3 draws about 6mA of current at idle. That works out to about 4 days of continuous operation.
Just to scratch off a scab: PLENTY of time for somebody uninformed to find a partially deployed rocket and potentially get hurt.
 

plugger

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Here's a link:

A fresh 9V battery has a capacity of 550 mAh. An RRC3 draws about 6mA of current at idle. That works out to about 4 days of continuous operation. Useful life is probably less than that, but I wouldn't want to push limits when pyrotechnics are involved.
Apologies for my implied sarcasm, I know it's not always easy to pick up in forums. My point was more to the fact that like most things, proper component selection should be considered. There's no requirement to run a cell that big as your math succinctly highlights. For my Ravens I pretty much only use 138mAh batteries as they have more than enough power to fire 4 charges and run the FC for the entire flight. But it doesn't have enough juice to keep things powered for days continuously in the paddock.
 

LithosphereRocketry

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Apologies for my implied sarcasm, I know it's not always easy to pick up in forums. My point was more to the fact that like most things, proper component selection should be considered. There's no requirement to run a cell that big as your math succinctly highlights. For my Ravens I pretty much only use 138mAh batteries as they have more than enough power to fire 4 charges and run the FC for the entire flight. But it doesn't have enough juice to keep things powered for days continuously in the paddock.
The current draw estimate of the RRC3 is pretty high compared to what I would expect from typical microcontrollers used in rocketry. The Raven doesn't list a nominal power draw, but I wouldn't be surprised if it was significantly lower- one of the major selling points of the Raven4 is lower power draw compared to the Raven3. A lot of modern microcontrollers have power draw in the <<1mA range.

My point is that assuming the battery will run out isn't exactly robust safety procedure. Even with a 140mAh battery on an altimeter equivalent to an RRC3, a rocket launched Sunday afternoon will still be very armed when the farmer does their rounds on Monday morning.
 

AlexBruccoleri

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Apologies for my implied sarcasm, I know it's not always easy to pick up in forums. My point was more to the fact that like most things, proper component selection should be considered. There's no requirement to run a cell that big as your math succinctly highlights. For my Ravens I pretty much only use 138mAh batteries as they have more than enough power to fire 4 charges and run the FC for the entire flight. But it doesn't have enough juice to keep things powered for days continuously in the paddock.
For what it is worth, I strongly advise against picking a smaller battery. If anything you want lots of battery margin in case there is an issue and more power is drained. Design around having the ejection system be safe to handle for the flier and make sure you do not overly complicate it so it remains reliable for flight.
 

plugger

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For what it is worth, I strongly advise against picking a smaller battery. If anything you want lots of battery margin in case there is an issue and more power is drained. Design around having the ejection system be safe to handle for the flier and make sure you do not overly complicate it so it remains reliable for flight.
When it comes to Ravens, which is what I primarily use for dual deploy, picking a larger battery is not recommended1652665909214.png
 

AlexBruccoleri

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When it comes to Ravens, which is what I primarily use for dual deploy, picking a larger battery is not recommendedView attachment 518857
Oh definitely follow the altimeter/flight computer guidelines! My point was not to pick a battery that is small to keep the idle time low. A battery could be weaker than spec, not fully charged, maybe the temperature is not ideal, maybe more current is drawn than expected etc. I recommend going with lots of margin, so long as you stay under the specs for the electronics.
 

rocket_troy

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When it comes to Ravens, which is what I primarily use for dual deploy, picking a larger battery is not recommended
Easy Solution - put a suitable shunt in series with either the rails or the squib.

Or use one of these either on its own or (if you need more than 2A) in parallel with a small ultra cap.


TP
 
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Easy Solution - put a suitable shunt in series with either the rails or the squib.

Or use one of these either on its own or (if you need more than 2A) in parallel with a small ultra cap.


TP
Shunts go in parallel with the load. A shunt directs the current around the load. A shunt limits the current at the load by diverting it. If a shunt is a dead short, it protects the pyro from firing as all current will go through the shunt. It does not limit the total current supplied.

You mean a a low value resistor in series with the pyro.
To compensate for the fact the designer forgot to implement current limiting at the design stage and after the first revision....and now we've all got to find a solution to a problem that shouldn't have been there in the first place. Just throwing that out there.....:(
 

plugger

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Easy Solution - put a suitable shunt in series with either the rails or the squib.

Or use one of these either on its own or (if you need more than 2A) in parallel with a small ultra cap.


TP
Tbh Troy I don't think I've got a problem, but thanks for the recommendation. I actually like the fact that I can run the Raven on such a small LiPo. Also, I've got a hard rule to NEVER use a battery with an integrated circuit board, which is what I assume that board is on the LiPo you linked to. I'm in the hole for well over half a k from flying one of those with a TeleMetrum v1.0 a decade ago. The Altus Metrum batteries shipped with TeleMetrum kits that would turn off the board when it tried to fire an ejection charge.

FixBattery link

1652675659355.png
 

rocket_troy

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Also, I've got a hard rule to NEVER use a battery with an integrated circuit board, which is what I assume that board is on the LiPo you linked to. I'm in the hole for well over half a k from flying one of those with a TeleMetrum v1.0 a decade ago. The Altus Metrum batteries shipped with TeleMetrum kits that would turn off the board when it tried to fire an ejection charge.

Interesting. I can see where you're coming from.

Something I never considered. The ultra cap in parallel would deal with that, but it's a good point to be mindful of.

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Tbh Troy I don't think I've got a problem, but thanks for the recommendation. I actually like the fact that I can run the Raven on such a small LiPo. Also, I've got a hard rule to NEVER use a battery with an integrated circuit board, which is what I assume that board is on the LiPo you linked to. I'm in the hole for well over half a k from flying one of those with a TeleMetrum v1.0 a decade ago. The Altus Metrum batteries shipped with TeleMetrum kits that would turn off the board when it tried to fire an ejection charge.

FixBattery link

View attachment 518886
Altus metrum supply batteries that specifically do not have the battery protection circuit board fitted.
These protection circuits typically also turn off the power from the battery if the voltage falls below a set level. So you might get a situation where the battery is marginal because it's been on the pad for a bit, launches ok, fires a pyro and switches itself off and of course anything downstream. They're best avoided for a mission critical application.
I'm not saying this is likely to happen, just it's possible. Low probability/high consequences in your risk assessment. So if possible, don't do it.
I can only see 3 batteries on the Hobbyking site that seem to have this circuit fitted. There's no mention in the product description that it has a protection/BMS circuit fitted either. You were a bit unfortunate choosing just the wrong one... :)
 
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plugger

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Altus metrum supply batteries that specifically do not have the battery protection circuit board fitted.
These protection circuits typically also turn off the power from the battery if the voltage falls below a set level. So you might get a situation where the battery is marginal because it's been on the pad for a bit, launches ok, fires a pyro and switches itself off and of course anything downstream. They're best avoided for a mission critical application.
I'm not saying this is likely to happen, just it's possible. Low probability/high consequences in your risk assessment. So if possible, don't do it.
I can only see 3 batteries on the Hobbyking site that seem to have this circuit fitted. There's no mention in the product description that it has a protection/BMS circuit fitted either. You were a bit unfortunate choosing just the wrong one... :)
If you clicked on the link I provided you'd see the page Bdale posted which is a detailed guide regarding how to remove the batteries. I didn't chose the wrong battery, AltusMetrum did. They were shipped with TeleMetrum v1.0 kits and would work fine until you tried to fire a charge. I know this as I flew mine twice before it sacrificed itself to the ground gods. First two flights I was flying it for GPS tracking, hence not encountering the fault.

1652684386124.png
Edit: Altus Metrum sources their LiPos from Spark Fun, which for the most part all come with the voltage protection circuit.
1652684949554.png
Spark fun lipos
 
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If you clicked on the link I provided you'd see the page Bdale posted which is a detailed guide regarding how to remove the batteries. I didn't chose the wrong battery, AltusMetrum did. They were shipped with TeleMetrum v1.0 kits and would work fine until you tried to fire a charge. I know this as I flew mine twice before it sacrificed itself to the ground gods. First two flights I was flying it for GPS tracking, hence not encountering the fault.

View attachment 518898
Edit: Altus Metrum sources their LiPos from Spark Fun, which for the most part all come with the voltage protection circuit.
View attachment 518899
Spark fun lipos
Must have bought mine after then. 2013.....I remembered it as being specifically mentioned. Obviously from the hard lesson someone got.
 
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