Battery choice

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Gunstar

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I'm getting back into the hobby and I need to make a change in my home made launch system. It was built to use polapulse batteries (batteries that were built into the old Polaroid camera film packs). That isn't an option any longer so I need to modify it. I'm doing low power rocketry, with the possibility of clusters of 3 or 4 D engines at most. Would 4AA batteries give enough juice for that, with some to spare for the power LED and a piezo buzzer that sounds when the circuit to power the igniters is active? What about using M21/23 N-cell batteries, they are 12V and half the size of a AAA but I'm not sure how much current they give, or should I go with 1 or 2 9V batteries?

Also, the power source used to fire the igniters is at the launchpad, the controller uses a 9V to trip a relay at the launch pad that closes the circuit to light things up.
 
Many are switching to using 4s LiPo batteries, which are easily available at local hobby shops (aka LHS) or from online vendors like HobbyKing. I too have an old PolaPulse battery launch system (early to mid 80's iirc) that came in a Space Shuttle Launch System kit, still have the rocket, pad and launch controller. 12V is needed for small clusters and the more current the better.
 
Avoid the 123's, they are expensive and weak.

The 4s LiPo recommendation is a good one, or qty. 3-4x 18650's in an AA holder
 
Keep in mind, if you go with a LiPo, you'll need a charger for it. A lot of people use a car jump starter. 12 volts and more than enough current.
 
I'm surprised nobody suggested sealed lead-acid batteries yet. I have a 7Ah 12V built into my controller... I've never had it fail to light anything. The only failures have been shorted-out Estes igniters- even on those, it puts out enough current to melt a hole in the little plastic retainer ring on E2X rockets...

qquake2k, I assume you mean a car jump starter (lead acid as well, I would assume, so that would be a suggestion of a SLA battery) as the battery itself, not to charge LiPos? Otherwise that could get, um, interesting...
 
Isn't that's a bit overkill for low power rocketry?

Not at all. That’s all our club has used for both HPR and smaller for 16 years. Igniters start right up with no hesitation. Batteries are cheap and durable and last a long time. In those 16 years I’ve only had two batteries fail to take a charge.
 
A small (say ~1000-1250 mAh) 3s or 4s LiPoly will be PLENTY, with the caveat about charging above. A small 12V lead acid gel battery is also a good alternative....again with the caveat that you have or get an appropriate charger.

With LiPolys - even smaller ones - providing enough current is not an issue as long as your wiring is adequate. What sort of igniters are you planning to use for your clusters?

Be aware of that LED and the dropping resistor going into it when choosing the battery - you may need to change it, especially if you go 4s LiPoly, which are 16.8V fully charged.
 
qquake2k, I assume you mean a car jump starter (lead acid as well, I would assume, so that would be a suggestion of a SLA battery) as the battery itself, not to charge LiPos? Otherwise that could get, um, interesting...

Actually, I was referring to one of the newer compact jump starters. They have lithium ion batteries, I believe. They come with a charger, so that's not an issue. Most also have at least one USB port to charge your phone, etc. 300 amps would be more than enough for any low power cluster. And you could use it for mid power, if you get into that. Plus, it will even start your car!

https://www.amazon.com/dp/B074WM8855/?tag=skimlinks_replacement-20
 
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The one linked to above does NOT come with a charger - it expects you to provide it with a USB-type 2A charger.

Take 300A with a grain of salt. The 8Ah LiPoly battery inside might be able to deliver 300A (briefly) into a short circuit. That says nothing of whatever is downstream (like your wiring - or even the short cable with the jumper clamps that comes with it).

That said, I expect that battery could easily serve the OP's need after some fun with connections. I would love to see the end to which the jumper cable attaches to see what the options are there.
 
I like to use small Sealed Lead Acid 12v batteries. I used something around 2.4 amp-hour battery for years, which was more than enough for a few hours of launching - around 2"x3"x3". It lasted around 8 years before it wouldn't hold a decent charge. I'm using a larger one now, only because it was free, from a UPS whose electronics failed.
 
I'm surprised nobody suggested sealed lead-acid batteries yet. I have a 7Ah 12V built into my controller... I've never had it fail to light anything. The only failures have been shorted-out Estes igniters- even on those, it puts out enough current to melt a hole in the little plastic retainer ring on E2X rockets...

I used to use my old Centuri 12V launch controller with one, had it for starting R/C gas planes and helicopters. FYI, you can use a 6V alkaline lantern battery with Estes igniters too.... they work well.
 
LiPoly data point: I have an 11-year-old three cell 1250 mAh Electrifly LiPoly pack in one of my Estes PSII launch controllers (it's plugged into the aux port inside). It launched probably 15 TARC flights last weekend and more than a few LPRs prior to that over the past few months since its last charge. I charged it this week - it was at 92% state of charge before I recharged it (per the info display on one of my FMA Direct [now RevoLectrix] Cellpro 4 chargers).
 
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