Can I launch a four motor cluster with an Estes Pro Series II launch controller?

[Sebbst]

Today I participated in a school rocket club launch and used the Pro Series II launch controller to launch 5 low powered rockets (Estes b4-6) before attempting to launch a Klima Andromeda as a sort of finale for the day. The launch controller has 9 volts of power, and the Apogee website says that it's good for launching cluster rockets. When I hooked up my four 18 mm Estes BP motors, they didn't ignite, so I re-hooked them up and tried again. The nichrome wire on the igniters was still on, so I know that the igniters didn't fail to light the motors.

Was this failure due to a lack of charge on the batteries in the launch controller? Or was it because 9 volts just isn't enough?

If any experienced rocketeers can tell me what they think went wrong I would really appreciate it, since I don't want to buy the wrong thing.

Thanks!

 

[smstachwick]

5 seems a little much. I’d go for no more than 2 or 3, although I admit I’m not super knowledgeable about this system’s specs.

Most big clubs use LiPo or even lead-acid batteries to delivery a ton of current and make igniters really zip.

 

[n3tjm]

9vt battery is bairly enough to start 1 estes igniter. Best to use with lower current igniters.

 

[Scott_650]

The PSII controller, with fresh alkaline batteries, should work fine on a 4-motor cluster. If you really want to maximize your chances you can use a 3 cell, 11v LiPo through the included JST connector, though from what I’ve read finding an off the shelf LiPo with that connector can be a challenge, plus you then need a proper LiPo charger.

Fresh batteries make a big, big difference - I use NiMH rechargeable “C” cell batteries in mine. NiMH aren’t ideal, I believe alkalines are better at dumping power than the NiMHs but being rechargeable is worth the slightly lower possible performance to me. I’ve done multiple 2-motor cluster launches with my PSII controller using both alkalines and rechargeables but I’ve also had mine conk out with supposedly fresh (per the date on the package) alkalines.

 

[heada]

If you assume the igniter has 1ohm of resistance, then that 9v source needs to provide 9amps of current to light the igniter. Within the possibility of a fresh 9v battery. Now if you use 5 igniters, that gives an effective resistance of 0.20ohm and would require 45amps and nearly no 9v battery can provide that. If you were to upgrade that battery to a 3S lipo battery, it runs at 11v and can source much more current and would light 5 in parallel with ease.

(lots of assumptions made above like resistance of the igniter, no losses due to internal resistance or wire length etc.)

 

[kuririn]

IIRC there is a lead from the PSII controller for an external power source, is there not?
So you can hook up a 12 v. battery with plenty of amps. Could be a LiPo car jump starter, could be a small portable lead acid battery, lots of options.
Edit: No external lead, there is an internal socket for an alternative battery source.

 

[therling]

I'm just finishing up a two-engine cluster rocket, so before I take it out to launch I did a test run on my Estes launch controller that I modified by adding a pair of alligator clips to which I can connect any battery, such as a Li-Po car jump start battery. That quickly fired up several pairs of test igniters (not installed in motors). I also had success trying a 14-16 Volt rechargeable battery I harvested from a robot vacuum cleaner.

 

[therling]

How are you connecting all the igniters? With multiple clips for each pair of igniter leads? Igniters must be connected in parallel for all of them to fire correctly.

Make sure all the contacts are clean to reduce any resistance caused by carbon deposits or oxidation. A pencil eraser can remove such crud that may be preventing the igniters from receiving enough power. Also make sure the igniter leads aren't shorting by coming into contact with each other.

 

[Sebbst]

How are you connecting all the igniters? With multiple clips for each pair of igniter leads? Igniters must be connected in parallel for all of them to fire correctly.

I twisted the leads together and attached the alligator clips to those groups.

 

[Sebbst]

After reading all of this, I'm fairly confident that I ran out of battery power due to the amount of rockets we launched. I'm going to buy some more alkaline batteries and go back to the launch site in a few weeks.

Thanks for the explanations!

 

[Sebbst]

5 seems a little much.

It was one at a time

 

[smstachwick]

It was one at a time

I see, thanks for clarifying.

I think the catalog displays three motors going at a time. More than that and I’d think you’ll want external power.

 

[Antares JS]

I would not use the 6 C batteries for more than two motors due to the hesitancy I experienced when trying to light two motors. I strongly advise using a LiPo. It is a bit annoying finding a 3S, 20C LiPo with a JST connector but it is worth it for the increased reliability. Unfortunately the one I bought a few months ago is listed as no longer available.

 

[heada]

I would not use the 6 C batteries for more than two motors due to the hesitancy I experienced when trying to light two motors. I strongly advise using a LiPo. It is a bit annoying finding a 3S, 20C LiPo with a JST connector but it is worth it for the increased reliability. Unfortunately the one I bought a few months ago is listed as no longer available.

I've never purchased this one before nor this brand but 3S lipo with JST connection, 40C and 800mAh. Should be able to fire 4x Estes igniters in parallel without issue.

https://www.amazon.com/Gens-ace-War...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[Antares JS]

I've never purchased this one before nor this brand but 3S lipo with JST connection, 40C and 800mAh. Should be able to fire 4x Estes igniters in parallel without issue.

https://www.amazon.com/Gens-ace-War...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

Might want to double check whether you can use that. IIRC, the instructions call for 20-30C. Mine is 3S, 20C, 1000mAh.

 

[kuririn]

Might want to double check whether you can use that. IIRC, the instructions call for 20-30C. Mine is 3S, 20C, 1000mAh.

And might not fit inside the case. I checked the instructions and there is no external lead, there is a jst socket that you can hook up an alternative power source to. So I was mistaken.

The Estes website says that the 6 C batteries can handle up to a two engine cluster.
So your Andromeda with four motors will need something with more juice.
Instructions say an 8-10 cell NIMH with 1000 mAh will fire up to four igniters.
A 3 cell LiPo will do 6 igniters (minimum 1000 mAh).
Getting either in the shape of 8 C batteries so it fits in the case is a challenge.

 

[Antares JS]

Instructions say an 8-10 cell NIMH with 1000 mAh will fire up to four igniters.
A 3 cell LiPo will do 6 igniters (minimum 1000 mAh).
Getting either in the shape of 8 C batteries so it fits in the case is a challenge.

Not really a challenge to fit it in the case at all. My LiPo is way smaller than six C batteries and is supported in place in the case by three of the battery-holding springs.

The hard part is finding a LiPo that meets the 3S, 1000mAh requirement while also having a JST connector. Most LiPo's that size seemed to have bigger connectors.

 

[kuririn]

Not really a challenge to fit it in the case at all. My LiPo is way smaller than six C batteries and is supported in place in the case by three of the battery-holding springs.

The hard part is finding a LiPo that meets the 3S, 1000mAh requirement while also having a JST connector. Most LiPo's that size seemed to have bigger connectors.

I wonder if this would work?
https://www.amazon.com/GOLDBAT-1000...ah+with+c+humps,+jst+connector,aps,333&sr=8-2

 

[CalebJ]

Might want to double check whether you can use that. IIRC, the instructions call for 20-30C. Mine is 3S, 20C, 1000mAh.

This is where battery ratings throw me... Wouldn't a higher C rating just indicate the ability to handle a higher instantaneous discharge?

 

[heada]

Amazon has a few (3+) that meet 3S, 20C 1000mAh with JST connector. Just have to pick one you like.

C rating is the maximum discharge rate and it used to calculate discharge current.

For a 1000mAh 20C battery, it can maximum discharge 20A (20*1000/1000) A 800mAh 40C battery can maximum discharge 32A (800*40/1000) It also comes into play with recharge rates. Most higher-end lipo charges allow you to set the charge rate and recommend a rate based on the C rating (for example, 0.1C to 5C). I always charge at 1C to be safe.

 

[CalebJ]

Amazon has a few (3+) that meet 3S, 20C 1000mAh with JST connector. Just have to pick one you like.

C rating is the maximum discharge rate and it used to calculate discharge current.

For a 1000mAh 20C battery, it can maximum discharge 20A (20*1000/1000) A 800mAh 40C battery can maximum discharge 32A (800*40/1000) It also comes into play with recharge rates. Most higher-end lipo charges allow you to set the charge rate and recommend a rate based on the C rating (for example, 0.1C to 5C). I always charge at 1C to be safe.

Thanks. My question was more regarding the downside to using a battery with a C rating higher than the 20-30 Estes recommends. Is that actually a concern?

 

[heada]

Wire or trace thickness could be an issue. Too thin and they'll fail with a higher cirrent. I doubt the differences we're talking about would make a difference.

 

[kuririn]

I'm going to buy some more alkaline batteries and go back to the launch site in a few weeks.

 

[Steve Shannon]

I would try four small electric matches connected in series. The current will be exactly the same in all four matches. If in doubt, try it without motors first, just to make sure it works.

 

[Back_at_it]

Yes but I highly recommend that you buy new, good quality C cells or better yet, get yourself a 2S LiPo and use that.

I recently tried flying a 3 motor cluster on the C cells that were about 6 months (maybe 250 launches) old and it would only light one igniter.

For giggles I got home and tested three igniters using the 2S LiPo and they all fired immediately. I'm looking for a launcher that would allow me to use some of the 3S LiPo packs I have laying around for my RC Cars. Those would probably fire any clusters I could dream up.

 

[Arnie]

Yes but I highly recommend that you buy new, good quality C cells or better yet, get yourself a 2S LiPo and use that.

I recently tried flying a 3 motor cluster on the C cells that were about 6 months (maybe 250 launches) old and it would only light one igniter.

For giggles I got home and tested three igniters using the 2S LiPo and they all fired immediately. I'm looking for a launcher that would allow me to use some of the 3S LiPo packs I have laying around for my RC Cars. Those would probably fire any clusters I could dream up.

You might consider an Estes Command Controller. I have one I'm interested in selling

 

[Back_at_it]

You might consider an Estes Command Controller. I have one I'm interested in selling

A buddy saw my post and said he has a Aerotech Interlock controller that should work that I can have. I'm going to try that out first.

I'm thinking I can simple replace the large car battery clamps with a high current "Deans" style connector to allow me to use my 3S 6000Mah LiPo packs. That would be 12.6V fully charged and should launch anything I can dream up in the near future.

 

[therling]

Estes publishes a thorough discussion of the amount of power needed for their igniters. Voltage is only one part of the equation. What's just as important is the current.

Estes says their igniters need 2 amperes of current. Multiply that by the number of igniters used in a cluster rocket and you quickly increase the demand for higher amperage. You also have to take in account the resistance of the wire lead to and from the igniter.

Page 14 has all the relevant numbers and formulas.

https://estesrockets.com/wp-content/uploads/Educator/2811_Estes_Model_Rocket_Launch_Systems.pdf
The car jump start battery I have is rated at 600 amps and cost me about $50. It's really a handy thing to have, especially if you drive anywhere that has spotty cell phone coverage.

 

[Ez2cDave]

It all depends on your choice of igniters . . .

"Chinese" eBay electric matches should be okay BUT, if there is ANY doubt, sacrifice 4 igniters to see the result !

Dave F.