# 3D PrintingDeWalt Battery launcher

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#### Chris948

##### Member
Cheapo 12v battery (edit, I have a 12v, but 20v batteries could work), random electronics from China. Garage door opener relay kit isn't up to code for legit launches, but it works for the local field where my kids want to push the button, but don't like loud noises.

Was a bit small to wire everything in. If I had to do it again, I'd probably make it bigger. Ordered a keyed switch as well but I guess that boat got lost.

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#### cwbullet

##### Obsessed with Rocketry
Staff member
TRF Supporter
Global Mod
Can you do a build thread with parts? I would love to build one to test my igniters.

#### Chris948

##### Member
Hey, I'll post the parts, I'll upload some pictures of the internals when I can.

I just uploaded the files here: https://www.thingiverse.com/thing:5030817

Switch - https://www.aliexpress.com/item/32859201158.html
Lights - https://www.aliexpress.com/item/32808739651.html
Garage Door Opener (has a setting to activate the relay as long as the button is pushed) - https://www.aliexpress.com/item/4000317757430.html
2 wire Connector (makes my life easier) - https://www.aliexpress.com/item/4001276108401.html
Key that got lost somewhere over the pacific - https://www.aliexpress.com/item/4000878482949.html
Fuse holder seems like a good idea - https://www.aliexpress.com/item/1005002823560204.html

Edit 4, battery: https://www.ebay.com/itm/402974793299

I need to test the fuses, not sure how small I can go without blowing them.

Like I said, it could be done safer, and no doubt way better. We only do low power stuff, so I don't have as many concerns as many people on here.

edit, you don't want my chicken scratch electronics notes (i did it wrong the first time) but a good thread is here. https://www.rocketryforum.com/threads/a-launch-controller-design-for-idiots.157619/#post-1986781

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#### Bravo52

##### Well-Known Member
What a great idea!

Thoughts on how long the battery will last at the field (for LPR)? However, considering that those who use battery powered tools would likely have multiple batteries, it probably wouldn’t be an issue.

BTW, I got the dreaded "404 Error, You've reached the end of the Thingiverse" error...

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#### Chris948

##### Member
BTW, I got the dreaded "404 Error, You've reached the end of the Thingiverse" error...
Fixed, I think. Sorry about that.

It's not an original idea, I believe there are similar designs, just different battery brand. I already have dewalt.

I don't bring enough motors to the field to stress an estes 4AA pack, I can't imagine moving the needle on 12v 3ah.

#### cwbullet

##### Obsessed with Rocketry
Staff member
TRF Supporter
Global Mod
I like the idea. We need to design a circuit board.

Chuck

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#### Chris948

##### Member
I like the idea. We need to design a circuit board.

COL H
That would easy. I guess the requirements would dictate how affordable it is. I wanted to be in under $30. You could beat that with an esp8266 controlling a relay, but then you're launching a rocket over wifi, I'm not sure how acceptable that is. I was bracing for someone to comment that cars driving by might hit their garage door openers and launch my rocket. I'm sure it's technically possible, but probability is low, so I'm ok with it. Someone else may not. #### cwbullet ##### Obsessed with Rocketry Staff member Administrator TRF Lifetime Supporter TRF Supporter Global Mod That would easy. I guess the requirements would dictate how affordable it is. I wanted to be in under$30. You could beat that with an esp8266 controlling a relay, but then you're launching a rocket over wifi, I'm not sure how acceptable that is.

I was bracing for someone to comment that cars driving by might hit their garage door openers and launch my rocket. I'm sure it's technically possible, but probability is low, so I'm ok with it. Someone else may not.
I can have them made for less than 10

#### Grant_Edwards

##### Well-Known Member
Thoughts on how long the battery will last at the field (for LPR)?
For a 12V 3Ah battery, I would estimate 500-1000 launches (easily) with the "standard" Estes igniters.

I did a launch event with a girl scout troop yesterday. My launcher is powered by an 11V 1Ah LiPo battery (photo below). We did 40-50 launches, and the battery was still above 90%. That included 3 or 4 instances where the clips shorted after the launch and blew 10A fuses.

When I got the battery home, it took around 20 minutes discharging at a constant 0.6A to bring it down to the 70% charge level for storage.

The battery the OP mentioned above has 3X the capacity mine does.

#### Sandy H.

I like the project and have a bunch of Dewalt 20V Lithium Ion batteries for my power tools.

A question (to be clear, not a criticism, just trying to understand) do Li Ion batteries tolerate dead shorts well? I tried a similar launcher with really old NiCADs years ago and the batteries failed to charge after a few launches. They were old, but I wasn't sure if the launcher killed the batteries vs the age. I know lead-acid batteries are very tolerant of a dead-short (current limiting by physical constraints), but I thought that RC LiPo batteries didn't like a dead short due to large current sourcing. I'm just curious if the regular drill batteries are good with that kind of load or not. I have no idea and have thusly shied away from trying it for a launch or test platform as I like my batteries. . .

I could see a really cool group project/3D printing/whatever coming out of this. Seems like it would fill a void for small/lone wolf launches. Looking forward to further development and would be happy to participate in a group project aspect if that would be helpful.

Sandy.

#### beeblebrox

##### 8 C6-0, 12 D11-9, 20 D20-0, 20 E5-0, 3 Cinerocs
I was told I could not use a wireless controller at MDRA launches, but I do use my controller elsewhere, I have a standard Bilusocn fireworks cue controller set. I got three boxes each with 4 channels and one remote. I use 2 channel outputs for continuity and launch, output of cues are 6v and as is can ignite e-matches, which is what they are designed for. I have the output trigger a relay inside the box for continuity and launch. Range is 400 feet. much further than a wifi link. Batteries are a pair of 7.5ah 12v gel cells. they last a long time. I have a smaller cheap and dirty system with a 1ah gel cell 12v. that did not run down using it all day.
I love the Dewalt battery idea though, wish I thought of that. I hate having so many different things using different chargers...
Therefore you get extra KUDOS!!!

link for cue system, although I would probably not buy one right now due to shipping problems... $29.50 Link for cue system in the USA -$39.58

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#### Chris948

##### Member
I got three boxes each with 4 channels and one remote. I use 2 channel outputs for continuity and launch, output of cues are 6v and as is can ignite e-matches, which is what they are designed for. I have the output trigger a relay inside the box for continuity and launch. Range is 400 feet. much further than a wifi link.
Yeah... You win

#### Lee

I am impressed with how long my 20 volt Dewalt drill and impact driver lasts and have wondered about alternate uses of the rechargeable batteries such as launching rockets. I was puzzled with how to connect the battery. Then I found this on Amazon for $12. Power Wheel Adapter for DeWALT 18V/20V Dock Power Connector 14 Gauge Robotics, ABS Materials Portable DIY RC Toys Adapter Set(with Wire Terminals) #### BEC ##### Well-Known Member I am impressed with how long my 20 volt Dewalt drill and impact driver lasts and have wondered about alternate uses of the rechargeable batteries such as launching rockets. I was puzzled with how to connect the battery. Then I found this on Amazon for$12.
Power Wheel Adapter for DeWALT 18V/20V Dock Power Connector 14 Gauge Robotics, ABS Materials Portable DIY RC Toys Adapter Set(with Wire Terminals)
View attachment 488378
And there are adapters like this for lots of different brands — Ryobi, Milwaukee, Ridgid, Black and Decker, Makita…. Hmmmmmmm……..

For powering a launcher any of these will be more than enough. I’ve been flying all year using an Estes PSII controller with a battery just a touch bigger than the one Grant Edwards showed inside. I haven’t recharged it. (Gotta love how lithium batteries don’t self-discharge, too.)

I like the project and have a bunch of Dewalt 20V Lithium Ion batteries for my power tools.

A question (to be clear, not a criticism, just trying to understand) do Li Ion batteries tolerate dead shorts well? I tried a similar launcher with really old NiCADs years ago and the batteries failed to charge after a few launches. They were old, but I wasn't sure if the launcher killed the batteries vs the age. I know lead-acid batteries are very tolerant of a dead-short (current limiting by physical constraints), but I thought that RC LiPo batteries didn't like a dead short due to large current sourcing. I'm just curious if the regular drill batteries are good with that kind of load or not. I have no idea and have thusly shied away from trying it for a launch or test platform as I like my batteries. . .

I could see a really cool group project/3D printing/whatever coming out of this. Seems like it would fill a void for small/lone wolf launches. Looking forward to further development and would be happy to participate in a group project aspect if that would be helpful.

Sandy.
I’m sure that LiPolys don’t like a dead short for long, but since they can source so much current, I’d be concerned about the rest of the wiring. You need a fuse or a breaker in at least one leg of the circuit. 10A would be plenty unless you’re running a 10-pad setup and you want to drag race all ten….

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#### Grant_Edwards

##### Well-Known Member
For powering a launcher any of these will be more than enough.
Way, way more than enough.
I’m sure that LiPolys don’t like a dead short for long, but since they can source so much current, I’d be concerned about the rest of the wiring. You need a fuse or a breaker in at least one leg of the circuit. 10A would be plenty unless you’re running a 10-pad setup and you want to drag race all ten….
I was using 10A automotive mini-blade fuses in my launch controller, but replacing them is annoying. I'm going to change to this 7A push-to-reset circuit breaker and see how that works:

https://www.amazon.com/dp/B00OGL7EXK

#### Grant_Edwards

##### Well-Known Member
I’m sure that LiPolys don’t like a dead short for long, but since they can source so much current, I’d be concerned about the rest of the wiring.
Just to reiterate, the sentence above should not be ignored. The battery I showed in the photo above is rated for 25A continuous 50A peak load.

LiPoly batteries can't tolerate a dead short for an extended period of time, but they probably won't need to. When used in a typical launch controller, something will melt and open the circuit before the battery is harmed. If you do wire everything with 4 gauge wire and 75A switches, then you will probably be able to cause serious damage to a LiPoly battery — and you don't want to do that. The videos I've seen of LiPoly battery ignition were caused by intentional overcharging, but they were impressive.

It could be that drill batteries are smart and contain current limiting circuitry that will prevent damage to the battery. If that's true, then you need to know what those limits are and whether they're low enough to prevent damage to your controller.

#### BEC

##### Well-Known Member
I was using 10A automotive mini-blade fuses in my launch controller, but replacing them is annoying. I'm going to change to this 7A push-to-reset circuit breaker and see how that works:

https://www.amazon.com/dp/B00OGL7EXK
I refurbished an old multi-pad controller I got from a teacher's estate and put a circuit breaker along those lines in it. I have no idea how it's worked in practice as I gave the whole setup to a new section and I don't think they used it before the pandemic brought group activities to standstill. I just have blade fuses on the leads between the battery and the controller on both my personal three-pad system and the club's 10 pad system....but I've never blown a fuse on either one.

There's no fuse or breaker in the Estes PSII controller (in which I have a 3s 1250 mAh LiPoly), but again, it's evident in a very short time whether there is an issue when trying to launch, so even if the igniter leads or the clips are shorted, there is only a dead short across the battery for a second or less. But in that controller, the internal wiring or that JST plug into which a LiPoly is connected would fail long before bad things would happen to the battery other than maybe causing it to puff mildly. That's a good distance away from one of those nasty fires.

#### Grant_Edwards

##### Well-Known Member
I just have blade fuses on the leads between the battery and the controller on both my personal three-pad system and the club's 10 pad system....but I've never blown a fuse on either one.
That's where I had my blade fuse connected, and it would get blown quite frequently when using steel blast deflector plates. When I switched to ceramic blast deflectors, the fuses lasted a lot longer. But, I still had to replace the fuse 3-4 times during an evening of 40-50 launches last week.
There's no fuse or breaker in the Estes PSII controller (in which I have a 3s 1250 mAh LiPoly), but again, it's evident in a very short time whether there is an issue when trying to launch, so even if the igniter leads or the clips are shorted, there is only a dead short across the battery for a second or less.
That sounds a bit scary. Maybe that battery won't put out as much current as the smaller 3S 1000mAh one I was using that was rated for 50C peak loads.
But in that controller, the internal wiring or that JST plug into which a LiPoly is connected would fail long before bad things would happen to the battery other than maybe causing it to puff mildly. That's a good distance away from one of those nasty fires.
The fuse/breaker in my launch controller is to protect the wiring and switches, not the battery. Various bits would start to glow and drip long before the battery was damaged. I've seen the Estes igniter leadwires (the non-nichrome wires) light up white (briefly) and then melt. If the clips themselves are shorted, I'm not sure what would be next to melt.

#### Chris948

##### Member
When I switched to ceramic blast deflectors, the fuses lasted a lot longer.
I was going to mask off the end of the clips that touch the igniters and electrical tape plasti-dip the rest of the clips. It's a lot of metal just asking for trouble.

#### Grant_Edwards

##### Well-Known Member
I was going to mask off the end of the clips that touch the igniters and electrical tape plasti-dip the rest of the clips. It's a lot of metal just asking for trouble.
I should try that. Some of the clips I use are traditional small alligator clips with plastic shrouds. Others are bare ones scavenged from Estes controllers. I should have been paying attention to see if the bare ones caused problems more often than the others.

#### BenCook

##### Member
This in my version of a Dewalt launch controller. For electronics I used a 300w 20amp constant current buck converter. Volts is dropped to 12 and current is limited to 6 amps. The buck converter has short circuit protection. When the current exceeds 6 amps then the voltage drops. It works perfectly. There is an automotive blade fuse in series with the battery in case something shorts internally. I also installed a 10 amp circuit breaker but that has proved unneeded due to the way the buck converter is working. The start button and led light up when continuity is there. The main disconnect for safety besides the switch cover is to unplug the leads which are an XT60 connector.

#### FredA

##### Well-Known Member
What's the point of the buck?
Nothing wrong with higher voltage - especially if you are going to light clusters.

#### Grant_Edwards

##### Well-Known Member
Does the light behind the start button tell you something different than the "center" LED between the toggle switch and the start button?

#### BenCook

##### Member
What's the point of the buck?
Nothing wrong with higher voltage - especially if you are going to light clusters.
It used it for current limiting and I had it already. It was only \$8. This was all just an experiment.

I am relatively new to anything but model rocketry. This was something I whipped up just for fun. I have yet to do anything with clusters. The good news is it would take just a few turns of a couple of pots to gain more voltage, amperage or both.

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#### BenCook

##### Member
Does the light behind the start button tell you something different than the "center" LED between the toggle switch and the start button?
Nope. I was intending to use the center LED for continuity but then when wiring realized that the button had an LED too so I just hooked that up as well.

#### Grant_Edwards

##### Well-Known Member
I see you're using an XT (60?) connector for the cable that goes to the pad. How are they holding up? I _almost_ did that with my two-pad launcher, since I had some on-hand. But in the end decided I wanted something more mechanically robust and easier to plug/unplug (but with some sort of mechanical retention). I ended up with two sets of these:

https://www.amazon.com/dp/B07DPR8T19

They work great, but are a bit larger than I expected. The specs on the Amazon page are accurate, I just wasn't paying attention...

#### BenCook

##### Member
I see you're using an XT (60?) connector for the cable that goes to the pad. How are they holding up? I _almost_ did that with my two-pad launcher, since I had some on-hand. But in the end decided I wanted something more mechanically robust and easier to plug/unplug (but with some sort of mechanical retention). I ended up with two sets of these:

https://www.amazon.com/dp/B07DPR8T19
View attachment 488606

They work great, but are a bit larger than I expected. The specs on the Amazon page are accurate, I just wasn't paying attention...
This whole thing was cobbled together with what I had laying around minus the circuit breaker which turns out I didn’t need anyway. I went with XT60 because that is what I had on hand.