Wednesday, September 1, 2010

Nerf Stampede - Voltage Increase / RoF Testing (Work-In-Progress)

With the Nerf Stampede now available in stores, i've managed to get alot more sets to tinker and modify. I will be posting up a series of Mod Guides on the Nerf Stampede soon.

In the meantime, here is a glimpse at how increases in voltage affect the Stampede's Rate-of-Fire (RoF).

Important Disclaimer: DO NOT attempt this modification unless you are familiar with electrical circuits and accept if your blaster is damaged in the process! Modify at your own risk!


Refer to this follow-up link below for the test results and optimal RoF recommendations:



  1. How long does it take for the stampede to heat up while using 22 volts?

  2. John,

    Well... at 22 Volts, i've only fired the Stampede in short bursts so far.

    At the moment, i still need my sets to be in working condition to test other modifications so i'll not be intentionally overloading their motors yet.

    But once i do get another spare Stampede, i'll probably do some load tests on the stock motor's voltage tolerance and post my findings. :)

  3. So how fast will it actualy shoot at?

  4. Hey sg.

    It looks like on that last 22 volt test you used the original battery compartment. Why did you use alligator clips then?

  5. Hey sg. Also, what stores in Singapore carry all the cool barrels that you use? Are there places in the US like that?

  6. what is the fire rate at 22 volts and can it still fire darts from the clip or drum with out jamming and being torn to pieces

  7. MetroNerf,

    For my voltage tests, i prefer to use different AA battery holders with various quantities of AA batteries so that i can see the effect of increasing voltage in smaller voltage "steps".

    Thats why i use alligator clips to interface temporarily with the AA battery holders just for testing purposes.

    The 3.7V Li-Ion Rechargable Batteries i use are also AA-sized, so i put them in AA to D battery converters, and since i wanted to test 6 of them, i simply used the original battery sled to hold those Li-Ion Rechargables encased in the converters.

    I'm actually going to use Li-Ion rechargables for all my modded Stampedes. Will probably just use 4 of them (with battery spacers in the battery sled) to get a more managable 16V-17V... easier to control in Nerf games. :)

    Barrels? You mean tubes and pipes for modding? Those can be purchased from hardware stores.

  8. So, is it any more complicated to upgrade the voltage on the Stampede than on the Vulcan?

  9. What's the amperage put out by those 3.7v batteries? And, to the point, if one increased the amperage and therefore the torque of the motor, do you think the PT could handle a slightly beefier spring?

  10. Julian,

    The methods to increase voltage on the Stampede are pretty much the same as on the Vulcan.

    1. sg nerf where can you get3.7volts Li-ion recharagable battries in sg pls reply
      tks balraj

    2. You can try Black Tactical at Funan IT Mall, they may have it in stock.

  11. David,

    If by amperage you mean the mAh rating, the 3.7V Li-Ion 14500 size rechargable batteries i currently use are rated at 900mAh. They have less capacity than normal 1.2V rechargables, but are offset by much higher voltage outputs.

    mAh mainly affects how long the battery lasts, it does not affect the speed of the motor... speed is determined by voltage.

    The torque of the motor is determined by the motor itself, so replacing the stock motor with aftermarket motors which have higher torque and voltage ratings is something that i'm currently testing too.

    I'm also currently testing various aftermarket springs with higher spring loads, those take some time to experiement with. I'll be posting up more findings once i complete my testing.

    1. Torque is directly proportional to current (Amperes) input providing the motor is the same

  12. I hope to see a full mod guide soon! If this is as good as it looks, then New Primary, ahoy!

    Anyway, is taking the various parts (bolt sled, PT, etc.) out of the gun as easy as a Longshot, or do you need to unscrew it and remove half the internals to get access?

  13. Julian,

    Well, i actually find the Stampede quite easy to dis-assemble and do mods, compared to the other blasters i've modded so far.

    The Stampede internals are mostly held securely in logical layers, so there are less chances of parts popping out or requiring constant manual alignment during re-assembly. :)

  14. I have a nerf Stampede I modded with 2 7.2 volt rechargaeble batteries and after firing two full clips (18 darts each) the gun fail to release the plunger. The bolt moves back and forth but never fires... Any ideas???

  15. z24cavalier3400,

    Do the streamline darts still chamber properly?

    If they do but don't fire out and just stack up in the barrel, the issue might be a bent or broken dart blocker door mechanism.

    Look into the barrel and through the side of the Stampede, you should see a small plastic "door" that closes to chamber a dart into the bolt and open to allow the dart to be fired out.

    Open up your Stampede and check that piece, if it is bent or broken, fix it. It could solve your issue.

  16. Just curious where you got your AA sized 3.7 volt batteries? I have been looking on a Hong Kong website, but all the 3.7 volt batteries are slightly larger than AA.

  17. Finn,

    The brand of 3.7V Li-Ion rechargeable batteries i use are called TrustFire.

    Note that i use "Unprotected" Li-Ion 14500 rechargeable batteries for the voltage increase mods, they are the same length and size as normal AA-sized batteries.

    I've found that "Protected" Li-Ion 14500 rechargeable batteries don't seem to work for such voltage increase mods, it could be due to the protection circuits stopping the current due to the high power draw.

    I recently posted up a Nerf Stampede Battery Guide at the NerfSG forum, lots of useful and important info about battery selections:

    It also has links to the online electronics shop that i get all my batteries and chargers from. :)

  18. Hey, I was wondering, does your stampede fire several more times even after you pulled the trigger. Mine has been firing 4 or 5 shots, even more even when I let go of the trigger. I have 4x 3.7v as well. Do you know how to solve this problem?

  19. Kenneth,

    I'm also currently running my modded Stampedes with 4 x 3.7V Li-Ion rechargeable batteries, but so far i've not experienced the extra shots happening after i release the trigger.

    But i have experienced that effect with higher voltage feeds, usually when i test them with 22-24 Volt feeds, the plunger tends to run for a few more shots before stopping.

    Perhaps you could check the trigger switch and see if you can try tweaking it to minimise extra shots fired when you release the trigger, could be due to the residual electrical current still flowing through the system.

  20. Hey SGnerf.

    I was trying to find 'Unprotected' 3.7V batteries and would this be one of them...

    I found another higher capacity one here..

    Can you tell when it's "unprotected" when it's described as...

    "TrustFire 14500 3.7V 900mAh without overcharge and overdischarge circuitry"

    Whereas 'protected' when described as...

    "3.7V(Voltage), 4.2V(Charge Protection Voltage), 2.75V(Discharge Protection Voltage)"

    Because it's a little confusing to tell. I've been reading your battery guide and stuff, I find the same looking batteries but they call it 'protected'.

    Also what does it mean by 'charge protection' voltage? Does that mean if it's unprotected you might overcharge the battery causing it to 'overheat'?

    Because I just realised when I was looking through these comments that you said unprotected is 'not the same'. When I was looking on Ebay... all I could find was protected =\.

  21. Thanh,

    I assume you have read my entire "Stampede Battery Guide" thread at the NerfSG forum:

    If not, do read it in full as it contains all the important information on what batteries to use, how they work and how to use them properly.

    To answer a few of your specific questions, the 18650 size batteries in the link you posted have higher mAh capacity but are much larger in dimensions compared to 14500 size batteries, so you'll need to do additional mods to fit 18650 size batteries into the Stampede.

    Those batteries what indicate that they don't have over-charge or over-discharge protection are Unprotected batteries.

    Charge protection in Protected batteries basically helps to prevent those batteries from being overcharged, but since most good Li-Ion chargers already have overcharge protection built-in, there is less of a need for that as Unprotected batteries are already protected by the charger itself.

  22. Yes. I have ready that battery guide :). I found it very useful because I needed to clarify what batteries I was going to buy! I saw on the charger you used by Trustfire Li-Ion.

    I've read the description and it says that when it finishes charging it shows a green light and stops charging.

    I was wondering if this is the one you bought... And how many did you buy because I realised that it only charges two at a time :(. How long does it take to fully charge?

    Also just noted that it says 3.6V charger... will that be fine for charging a 3.7V battery?

    I've also note from your guides that once the stampede starts shooting slower than it should be (perhaps back to it's stock ROF) that I should take the battery out and charge them again? So they don't go past the discharge level? (Assuming that 2.75V x 4 = 8Vs = bad for unprotected).



  23. Sorry, just found another type of charger which is a Li-Ion charger that is rated at 4.2V at 500mAh.

    Would this be fine with the trustfire batteries I'm purchasing?

    Sorry for being such a pain! But you seem like a really good person... Thanks for helping so far :)

  24. Thanh,

    I use this TrustFire TR-001 Li-Ion charger:

    So far, it has been working perfectly with the TrustFire 14500 Li-Ion rechargeable batteries that i'm using.

    As for preventing over-discharge in unprotected Li-Ion rechargeable batteries, once you detect that the motor starting to run slower, its an indication to recharge the batteries.

    I'd highly recommend getting a Multimeter so that you can test each battery to find out their voltage status and condition. I use something like this:

    Its a very useful tool for motorised blaster modders. :)

  25. Hey man, just wondering if you found a way to fit the trustfire 18650- if not- what would happen if I halfed the battery holder you've posted to extend the length a bit- the wiring wouldnt be affected right?

    If i can't do that- what about AA Switched battery enclosures (they are 69 mm in length so they would fit them)- i'm just not sure if they are wired in series or parallel- has to be series right?

  26. Chi-Rong,

    Check out an interesting DIY custom made casing for 18650 sized batteries that NerfSG forum member and expert modder "hanzo" posted up:

    Just an idea for your reference. :)

  27. I'm using 12 Li-Ion batteries (14500 model, AA sized @ 3.7 V 900mAH each)that are clustered in three parallel groups of four serial battery holders. For a nominal voltage output of about 16.6 V at 2700 mAH.

    I'm currently getting the extra shots issue (where the gun keeps firing for a number of shots after I release the trigger.

    Prior to this I had 12 AA batteries linked in serial (+ to - across each cluster of 4 batteries) for a nominal voltage output of 18.4 V; and I had no issues with over-firing

    I've also noticed there are some micro-Farad capacitors on the sides of the motor. Could this be what's causing the issue? Some kind of interaction with the lithium-ion batteries that is different from the alkaline.

  28. x5,

    This Stampede "auto-running" troubleshooting solution might help:

    If the above solution doesn't solve the issue, there are a few other factors that can cause it too.

    Check if there is anything slowing down the speed of the plunger returning to the open position, because its the return delay that causes the white half-gear to keep catching it before the plunger completes a full firing cycle, hence contributing to the "auto-running" issue.

    Check that your o-ring is allowing the plunger to move smoothly and without too much resistance, as any slowdown there will cause the "auto-running" issue too.

    For more information and discussion on this issue, check out the very useful Stampede troubleshooting thread at the NerfSG forum, after lots of time spent working on the blasters, we have managed to find solutions to most of the "auto-running" issues on modded Stampedes:

  29. Thank you for your prompt reply! But I'm afraid I must give you a greater explanation.

    First, here's the video of my working gun:

    Second, this is what good example of HvZ is:

    When the gun WAS working properly:

    I modded it based on instructions from your mod here with the doubled up spring (just twisted them together into a single double helix and then used a stationary foam pad cut as a washer to absorb the extra force of the plunger's impact, not attached to the plunger). Thus, I did NOT modify or replace the O-ring. The gun fired amazingly fast (making me a much feared enemy among the zombies), and with more than double the range it caused a major shift in tactics for both sides. Literally, from your concepts I made a game-changing piece of technology (albeit using alkaline batteries).


    Not too long after the game ended this past week (i.e. after plenty of use on the gun), the lithium batteries finally arrived late. After charging them fully (while keeping them chilled for an optimal first charge), I tried them out in the parallel arrangement I mentioned above...

    Problem #1 (resolved):

    The very first thing that happened was that the motor started spinning rapidly (no load) and the gun wasn't firing. After taking it apart I found the culprit in that the third torque increasing gear (the one right before the main gear that moves the rack & pinion gear) was actually made of two pieces just stuck together and one of the walls of the square "axel" support that the lower part pushes into had cracked (thus why it was slipping in place and not transferring the mechanical kinetic energy). To fix this I used a leveled-off fill of hot glue gun plastic into the void spaces and then superglued the "axel" as I reinserted it). The gun's transmission works again (#1 solved), however...

    Problem #2 (unresolved):

    The gun now continues to fire for awhile after the trigger is pulled. This is a problem because it wastes ammo and can continue to fire unexpectedly if I have to release the trigger while I move around.

    There have been only two changes that could be causing problem #2: the transmission reinforcement modification to the third torque-increasing gear, or lithium batteries (there was a voltage decrease actually from 18.4 to 16.6 V, and ampere-hours should have remained about the same at 2700 mAH, or 9720 Coulombs) The capacitors on the + and - terminal of the motor are rated at 140 uF each, which thus means:
    C*V = Q ; and C = 1/(1/140uF + 1/140uF) = 70 uF; 70*16.6 = ~3.227 mAH stored

    In short, either the LiCoO2 chemistry is different from the alkaline cell that has some effect on the capacitors or there is a mechanical cause for why the whole system keeps moving past the trigger's pull.

  30. Oh and about the catch control spring (

    I've encountered problems with that little spring on another Stampede, but from the experience with that one I learned my lesson and made sure it wouldn't pop out even again on future ones (electrical tape + superglue = close the hole in the catch control component FTW)


    I'm thinking it's still probably a mechanical cause but I can't rule out that it could be electrical, as I'm not that familiar with capacitors (which btw, why are they even on the motor in the first place? The wires leading out of those two little ceramic capacitors are the smallest wires in the circuit that I can see)

  31. Hmm, from reading the replies to that forum link you gave me it appears a cause I may not be familiar with could be in fact the plunger & tube assembly return spring, but...

    1) How could that be when it over shoots about 5 to 6 shots fairly consistently and that hitting the "safety switch off" kills the "infinite firing loop" effect?

    2) What could be done to make that spring stronger?

    Note: I actually did try twisting a second black spring from another stampede with it (double helix again) but of course is minimum compression length was doubled and this caused an issue. Special ordering a spring might be tricky... (it's not a size carried by any local hardware stores; key parameters being InnerDiameter, OuterDiameter, Compressed & Uncompressed length, and Spring constant (k))

    I shall await your reply as you have more expertise than I in this area, and I'm sure others will have the same questions as they read this blog page.

  32. x5,

    As mentioned earlier, the primary reason the "auto-running" issue occurs is because the plunger has not fully returned to the open position in time and the spinning half-gear (the white gear just below the plunger toothed rail) spins one full circle at higher speed and catches the plunger halfway and proceeds to push it forward again, and the process keeps repeating itself.

    Sometimes even if the trigger is released, the "auto-running" continues as there is a white inverted C shaped trigger mechanism that can't return back to the proper position to cut the circuit due to the plunger not returning back to the open position fully. Thats why you have to manually click off the power switch to stop everything.

    A more detailed explaination to this issue can be found in this thread post at the forum:

    Note its possible that parts in the Stampede can get worn, damaged or mis-aligned after some usage when operated at higher RoF so that could be the cause of issues too.

  33. x5,

    To further troubleshoot, open the Stampede casing and remove the spring in the plunger, then reassemble the plunger with the o-ring and parts still intact and then try moving the plunger to and fro to simulate the firing cycle.

    Do you spot anything slowing down or blocking the movement of the plunger?

    The whole plunger system should move forward smoothly without any resistance and the black return spring should snap it back smoothly to the open position very quickly without any delay or resistance.

    The main culprit of the "auto-running" issue has been the delay in the return of the plunger to the open position, so that is the area to focus on.

    Modders have tried stretching the black return spring slightly to temporarily increase its return spring load for faster return movement, and that method has worked for some.

    I've also worked on Stampedes which had bent internal components that created resistance in the movement of the plunger, so re-adjusting the parts back to original shape helped solve the issues too.

    I've even worked on one Stampede which had manufacturing variations from the factory and the plunger to casing fit was too tight so i actually trimmed the casing guide and applied synthetic grease to the contact parts to loosen the fit and it solved the issue.

    So there are many things that could affect the operation of the automatic firing, just have to troubleshoot step by step. :)

  34. I have a question. Is it safe to put 3.7 volt batteries?

  35. Iván,

    Using higher voltage batteries will increase the speed of the motor and improve the rate-of-fire, but that will also increase the wear and tear on the motor and mechanisms.

    Modders have to understand and accept the implications of modding blasters.

    As i always say... mod at your own risk! :)

  36. Got a question man,

    I'm wondering about a particular part on the stampede, i'm not sure whether its a capacitor or a resistor, its the squarish looking wire that extends out from the + and - area of the gun right where the battery sled would lock into- it's possible to replace that part by cutting it, and finding a replacement, re-soldering and shrinkwrapping it right?

  37. Chi-Loong,

    I'm not exactly sure what that part is either, 'cos i'm not an electronics expert... my electronics knowledge is "caveman" level at best, all basically discovered through pure trial and error. :)

    Perhaps you can check with friends who are more familiar with electrical systems, they would be better equipped to help you out.

  38. I got a question,
    When I use the 22 volt batteries how long do you think the motor will last until its blown?

  39. Robert,

    No idea... 22V is too fast for the clip system to keep up with anyways and that firing speed results in alot of jamming issues, so i don't run my modded Stampedes at that voltage.

    You can read about the follow-up voltage test results and recommendations here:

    I've been running my modded Stampedes at around 16-17V for the past few months and they are still working okay... so far.

    Though you are welcomed to run your Stampede at 22V and see how long the motor can last. Tell us about your findings too. :)

  40. Thanks for answering my last question but I got another one,

    What do you use to hold your double A batteries?

  41. Robert,

    I use AA battery holders or converter shells, you can get those from most electronics parts supply shops.

  42. I just put a 8AA battery holder in place of the battery sled...that's the only thing I changed. I fired about 32 rounds full-auto and over heated the battery holder, it stopped shooting and the springs that hold the batteries in place were so hot they melted back...did I do something wrong? do I just need to use short bursts?

  43. joshua,

    Your battery holder might be faulty and a short circuit may have occured within the holder's circuit.

    Try using another better quality battery holder.

  44. Hi SGnerf,

    Can u solve my problems:
    Yesterday,i've bought 3 RC Battery(7.2 volt each).After 1 week playing,the battery is out of power.I don't know how to charge it because i don't have any RC Cars..... Please help me SG Nerf......

  45. Xtroy,

    Simple... just buy a suitable battery charger for your RC battery packs.

  46. Dear SG Nerf,

    I can't find the charger that can charge my RC battery.I have gone to many shop but i can't find the perfect charger for my battery.There are many chargers ,but all of the charger can only charge seperated battery.

    Details of my battery:
    1)sticks together
    2)covered with green plastic
    3)hve 2 wire(black and red)

    Many of the shop keepers said that i've to buy the RC Car it self to charge the battery.I dnt wnt to do it,cuz RC car is not cheap it cost about $158.95 each.

    I hope that you find me other way to charge my battery... ;'(

  47. Xtroy,

    Most dept stores usually don't sell RC car battery pack chargers. They only sell those common chargers for AA rechargeable batteries.

    You have to go to RC car hobby shops and get the specific chargers for those RC car battery packs.

    Those specific chargers have connectors that will connect directly to your RC car battery packs. Just bring along your battery packs and show the hobby shop staff and they will recommend you suitable chargers for them.

  48. SG Nerf,

    Ouh,i've forget to tell you that i've cut the white thing at the end of the wire,and now it look like a normal wire connected to the RC battery,Hehe ;) sorry about the late info... =)

  49. hi how do you do to get by on 22 volts

  50. gettner,

    I use Li-Ion rechargeable batteries.

  51. I have tried to increase the voltage suppled to my stampede but find when I attach a 14v battery that the gun continues to fire even after I have released the trigger.

    Any ideas why, or how I can fix the problem?

  52. DougieB93,

    Read the earlier comments, here is a re-post of one of the discussions...

    This Stampede "auto-running" troubleshooting solution might help:

    If the above solution doesn't solve the issue, there are a few other factors that can cause it too.

    Check if there is anything slowing down the speed of the plunger returning to the open position, because its the return delay that causes the white half-gear to keep catching it before the plunger completes a full firing cycle, hence contributing to the "auto-running" issue.

    Check that your o-ring is allowing the plunger to move smoothly and without too much resistance, as any slowdown there will cause the "auto-running" issue too.

    For more information and discussion on this issue, check out the very useful Stampede troubleshooting thread at the NerfSG forum, after lots of time spent working on the blasters, we have managed to find solutions to most of the "auto-running" issues on modded Stampedes:

  53. hey well i was saudering my nerf parts to the battery sled and it wont fire. but the batteries work. is it becuase i removed the tan bow on the positive wire feed inside the nerf gun. if so what is its function??

  54. crakdice,

    That tan colored component is most likely a thermistor, its a safety component that limits current or acts as an overcurrent protector.

    Here is some info on it:

    By default, its supposed to be part of the circuit for safety, but i'm not sure how its removal would affect the actual operation of the circuit though.

    I guess you could try soldering it back to see if it works again.

  55. I tried to modify my stampede with two 9 volts, but i must have broken it. I tried soldering the wires from the gun directly to the batteries but nothing is happening. am I soldering the wrong wires, or have i just ruined it?

  56. Siriuslyharry,

    9V alkaline batteries have very low mAh capacity and limited discharge rate (different factors from voltage), they are designed for devices with low amp current draw, therefore not ideal for modding a blaster that requires higher amp current draws like the Stampede.

    Even if they work on motor systems, 9V run out of power quickly and you'll have to keep changing batteries which is costly.

    Most likely the particular 9V batteries you currently use don't have enough power to run the Stampede. Use other types of batteries instead.

  57. Thank you. would alkaline 9 volts work? could button cell batteries work as well? what would you recommend for a lightweight battery between 12 and 18 volts that would supply a high current draw and could be directly soldered in?

  58. Siriuslyharry,

    Well, as i've mentioned, 9V alkaline batteries have very low mAh capacity and discharge rate and run out of power very fast, so they are not cost effective to use at all... button cell batteries have even less mAh capacity so not suitable too.

    So far, the best compact yet light weight batteries i've used so far are unprotected 14500 size Li-Ion Rechargeable Batteries. They are AA sized and have high voltage (3.7V nominal, 4.2V fully charged) and high discharge rates, and can be used in existing battery compartments.

    You can read about them at my Stampede Mod Guide:

  59. I want help with my Nerf Stampede. Im new to modding, good at it, and I want my stampede to have more power. I bought an OMW 4KG Load spring and put it in, and it's not really amazing. I have another nerf gun with the stock, and the vulcan spring, (Suprisingly amazing) and it shoots better than the OMW spring, should I get a tougher load? Thanks

    1. John Rallo,

      Lighter load springs naturally result in less range improvements, so if you want to see more significant range increases, you will have to use heavier load springs.

      In my modded Stampedes, i usually install 9kg load springs... that offers the ideal combination of longer ranges while still retaining a high rate-of-fire and reliability.

      You can check out my various Stampede Mod Guides for reference:

      If you are keen on the same 9kg load springs that i use, i actually still have spare sets of my Stampede Mod Kits available, just refer to my trading thread at the NerfSG forum:

  60. can i us 10 1,5 AA batteries to have a 15 volt voltage???

    please reply soon

    1. Luis Nunes,

      Yes, i also used 10 x 1.5V batteries to get 15V in the video (there was abit of a typo, its not 16V).