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The Stampede that Stood Still

voltage increase not working...

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#1 Xervous

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Posted 14 August 2013 - 05:56 PM

So after all the work I've put into this Stampede it still refuses to work. The only other mods I've done are an aftermarket spring and AR removal. I've got 4x 14500 unprotected trustfires wired in, my multimeter confirms that the connection in the battery sled is good, but I don't even get a whisper out of the Stampede. It still runs fine with 6x Ds. Is there something I'm possibly doing wrong or is the stampede defective?
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UPDATE:

whenever I pull the trigger, the motor makes a small noise but otherwise nothing happens.

Edited by Xervous, 14 August 2013 - 11:46 PM.

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#2 Duke Wintermaul

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Posted 14 August 2013 - 06:23 PM

You've got the tray soldered in backwards. Switch the wires and you're golden.
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#3 Xervous

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Posted 14 August 2013 - 06:31 PM

You've got the tray soldered in backwards. Switch the wires and you're golden.


I'm no electrical engineer, but I think its wired correctly. Multimeter's black to the anode, red to the cathode. Doing this on one of the D batteries yields me a positive value on the needle, and for the battery sled also yields a positive value...

Since I can't post anymore today and I don't think it's against the CoC... I'll edit in some stuff here.

@ Mully
-Yes it works with D batteries and the aftermarket spring
-14500 unprotected (Grey) trustfires, ordered these a week ago when I realized I was using protected ones.
-All 4 batteries are currently reading around 4v. I'm slowly charging them up to 4.2

@azrael
-Yes, its measuring around the expected 16.8

Edited by Xervous, 14 August 2013 - 06:47 PM.

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#4 Mully

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Posted 14 August 2013 - 06:36 PM

Just to be sure, it works with D batteries, with the aftermarket spring right?
What kind of trustfires are you using? I had a similar problem with one of my 'Pedes once, I popped it open, checked all the circuits, got a hunch, tested the batteries on another blaster that I knew worked, and discovered that one of my trustfires had died. It sounds like you may have a similar problem.
The only other thing I can think of off the top of my head, is a faulty connection in the battery box...but that seems unlikely.
Btw, you're right, it is wired correctly.

Edited by Mully, 14 August 2013 - 06:39 PM.

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#5 azrael

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Posted 14 August 2013 - 06:46 PM

FWIW, I don't recommend soldering to those springs. I guess you're limited by the Trustfire's crappy current supply, but one time, I was lazy - the battery spring got so hot that it turned red and started smoking.
Not that a AA tray's battery retention springs are any better haha.

Your most obvious test since you have a multimeter is to make the tray functions. Are you measuring 16.8 volts from it on a full charge?
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#6 Xervous

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Posted 16 August 2013 - 03:40 PM

Seeing that other people were having this issue while using 4 trustfires but not with 3, I tried that but the blaster still does nothing more than a light growl when I pull the trigger.
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#7 Mully

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Posted 16 August 2013 - 06:09 PM

Seeing that other people were having this issue while using 4 trustfires but not with 3, I tried that but the blaster still does nothing more than a light growl when I pull the trigger.

Huh...when you pull the trigger, and the engine makes that growling sound, is it making any kind of smell? Have you taken out any of the locks, has anything else been done your stampede, aside from an after market spring, and AR removal? Did you open the gear box, or tinker with that area at all?
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#8 azrael

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Posted 17 August 2013 - 01:17 PM

Are you sure that the battery tray is even providing any power? Haven't heard confirmation that you measured the right voltage at the battery contact.
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#9 azrael

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Posted 17 August 2013 - 01:18 PM

EDIT: Woops, double post.
Let's make it useful, at least.

Are you sure there's no corrosion or anything that could mess up the contacts? Have you considered that you may have a cold solder joint? Cold solder joints are a poor electrical connection.
What solder and soldering iron did you use?

Edited by azrael, 17 August 2013 - 01:22 PM.

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#10 Xervous

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Posted 17 August 2013 - 02:13 PM

EDIT: Woops, double post.
Let's make it useful, at least.

Are you sure there's no corrosion or anything that could mess up the contacts? Have you considered that you may have a cold solder joint? Cold solder joints are a poor electrical connection.
What solder and soldering iron did you use?


I'm planning on opening the thing up (So many screws...) when I get the time and checking where the voltage drops are. Hopefully I'll get that done today. I move around a lot so I don't always have access to my tools.

The solder could be at fault, given it was mildly aged. The voltage measures correctly but obviously the current isn't up to par.
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#11 azrael

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Posted 17 August 2013 - 05:08 PM

The voltage measures correctly when measured where? At the point where it contacts the Stampede?

And the solder isn't about age, it's about technique and what type of solder it is. Still haven't mentioned the type of soldering iron (wattage mostly) and solder alloy.
If your technique isn't good, your solder joints will not be good. I can't tell from that pic is your solder joints are good, but it looks like the solder did not wet on the contact at all. Meaning not really all that good.


EDIT: Wait, what batteries are you using? Are they unprotected or protected Trustfores? Protected ones will not work.

Edited by azrael, 17 August 2013 - 08:32 PM.

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#12 Xervous

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Posted 20 August 2013 - 07:01 PM

The voltage measures correctly when measured where? At the point where it contacts the Stampede?

And the solder isn't about age, it's about technique and what type of solder it is. Still haven't mentioned the type of soldering iron (wattage mostly) and solder alloy.
If your technique isn't good, your solder joints will not be good. I can't tell from that pic is your solder joints are good, but it looks like the solder did not wet on the contact at all. Meaning not really all that good.


EDIT: Wait, what batteries are you using? Are they unprotected or protected Trustfores? Protected ones will not work.


I'm using unprotected (gray) trustfire batteries.

Testing the solder joints, they provide negligible resistance alongside the metal plates, though I don't know if this is relevant.

When firing with 6 D batteries, the voltage across the two panels on the battery sled dips slightly from 9 to about 8. When attempting to fire with the trustfire batteries, it drops to 0 volts.
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#13 Mully

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Posted 20 August 2013 - 07:30 PM

Maybe the battery tray has a thermistor built in towards the front somewhere?...
Where did you get the battery tray from?

Edited by Mully, 20 August 2013 - 07:31 PM.

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#14 Xervous

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Posted 20 August 2013 - 07:37 PM

this is the one that came with the stampede.

With 3 or 4 trustfires it doesn't work, but it does work with 2...
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#15 Mully

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Posted 20 August 2013 - 08:09 PM

this is the one that came with the stampede.

With 3 or 4 trustfires it doesn't work, but it does work with 2...

Oh whoops, my bad, I meant the AA battery tray.
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#16 Xervous

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Posted 20 August 2013 - 08:14 PM

Oh whoops, my bad, I meant the AA battery tray.


Its just a cheap little piece I picked up from radioshack.

Do note that I have reached my post limit for the time being. Any additional messages will be edited into this post and be labled as such @Whomever_I_Am_Replying_To

@Mully: I tried the ghetto holder and it still doesn't work. Problem is most likely stampede side.

@Hammy: Picture isn't the best quality, black on spring, red on tab

2@Mully: The batteries work fine in the rayven

Edited by Xervous, 20 August 2013 - 10:48 PM.

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#17 Mully

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Posted 20 August 2013 - 08:30 PM

Its just a cheap little piece I picked up from radioshack.

Then as I mentioned earlier, they're might be some kind of voltage restricting device built into the tray. May I suggest trying out a kind of ghetto Trustfire rig, to test if the tray is legitimate? What I'm suggesting is basically along the lines of, take a few pieces of wire strip them, and then tape/get them too touch the ends of the batteries, and then hook them up to your Stampede. I'd recommend taking apart your 'Pede for this, if it isn't already disassembled.

Edited by Mully, 20 August 2013 - 08:32 PM.

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#18 Hammy

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Posted 20 August 2013 - 09:53 PM

Dude, as already pointed out, your battery connector is connected to the battery sled in the wrong polarity.

The black wire should go to the spring.
The red wire to the tab.


There is no thermistor in the battery sled.

It should not matter if you solder the wires to the spring and tab, so long as the join is good and clean.

No other electrical mods are needed unless you want to remove all of the locks.
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#19 Mully

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Posted 20 August 2013 - 10:08 PM

The black wire should go to the spring.
The red wire to the tab.


There is no thermistor in the battery sled.

I think it's already like that man. As far as I can tell he did it correctly.

EDIT:

There is no thermistor in the battery sled.


I meant the RadioShack tray, sorry about that.

Double edit:
Your absolutely sure the all the batteries work?
Do you have any other blaster, like a Rayven or something to try them out on?

Edited by Mully, 20 August 2013 - 10:24 PM.

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#20 Hammy

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Posted 20 August 2013 - 10:14 PM

whoops, my bad :(
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#21 azrael

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Posted 21 August 2013 - 12:20 PM

I'm using unprotected (gray) trustfire batteries.

Testing the solder joints, they provide negligible resistance alongside the metal plates, though I don't know if this is relevant.

When firing with 6 D batteries, the voltage across the two panels on the battery sled dips slightly from 9 to about 8. When attempting to fire with the trustfire batteries, it drops to 0 volts.

That is a VERY clear indication that your AA tray does not work, either because of your solder, or because of the tray.

Dude, as already pointed out, your battery connector is connected to the battery sled in the wrong polarity.

The black wire should go to the spring.
The red wire to the tab.


There is no thermistor in the battery sled.

It should not matter if you solder the wires to the spring and tab, so long as the join is good and clean.

No other electrical mods are needed unless you want to remove all of the locks.

Wrong, the spring has a high resistance, and should not be soldered to. Excessive current draw can cause it to light on fire. This is a well documented problem with battery springs. Ideally, battery trays shouldn't use springs at all.

Edited by azrael, 21 August 2013 - 12:22 PM.

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#22 Hammy

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Posted 27 August 2013 - 04:45 AM

That is a VERY clear indication that your AA tray does not work, either because of your solder, or because of the tray.


Wrong, the spring has a high resistance, and should not be soldered to. Excessive current draw can cause it to light on fire. This is a well documented problem with battery springs. Ideally, battery trays shouldn't use springs at all.



Can you tell me the resistance of the spring?

I measure it at 0.1 ohm at room temperature, using a Fluke multimeter, leads compensated.
If it is conducting 1 A, then you have 0.1V drop and 100 mW power disspation.
Even if it was conducting 2A, then you have 200 mW dissipation, which is not much.

If 10 A, then 1V drop and 1 W power disipation (the wire may feel warm uinder this situation), but at 10 A, your Stampede would be probably be melting, if not all the wires and switches inside (if they are the stock ones) could not take that kind of current and would blow. If the batteries were giving such a large current, I believe they would catch fire before the spring got hot enough to set the battery tray alight.
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#23 azrael

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Posted 27 August 2013 - 11:51 AM

.1 ohms is pretty huge, IMO.
I doubt that is what it is, though.
I don't know the dimensions of the spring, and I don't really care too much, but here's some math from a flashlight forum:

Looking at #24 gauge bare copper wire which has almost the same
diameter as 0.022 inch wire, the resistance for 1000 ft is 20.8 ohms.
For 1 foot, it's 0.0208, and for 1 inch it's 0.001733 ohms.

The length of the helix is approx:
L=4.5 turns times 0.375 inches times pi=5.3 inches.

The increase in length due to the helix over the
circumference is only about 0.2 percent, so this increase
will be ignored.

5.3 inches times 0.001733 equals 0.00918 ohms total for a copper spring.

Knowing that the resistivity of SS is about 42.4 times higher than
copper, multiplying the total resistance times 42.4 gives us an
estimate of the total resistance of the SS spring.

R(SS)=0.00918 times 42.4 which equals 0.39 ohms total.

This number indicates something went wrong with the previous
calculation done in the previous post. I suggest checking
it for an error involving the conversion factors. Since rho
is given in ohm-cm i suggest working entirely in cm and cm^2
and redo the calculations.

That should give you an idea, at least.

You are underestimating stall current, meaning the current that a motor uses when it starts moving. It can be pretty big, depending on how many volts you're feeding the motor. As you increase the voltage, the current demanded by the motor increases too.

It's a pretty well documented phenomenon in in flashlight forums. MY WIRE wouldn't catch fire under those circumstances, I use teflon insulated stuff, it's pretty tough stuff. Also, my spring HAS gotten hot enough to catch flame. I had to put out my Stampede - this happened to me. Why doubt me?
I don't know anything about yours. I've used slightly higher gauges of this teflon insulated wire in robotic builds that consume over 100A at stall current. And it was fine. :)
You might be fine because Trustfires are honestly terrible batteries that cannot supply the current that these motors need. They have a poor discharge rating. If you use something that actually gives the motor what it needs, it is a different story. My rate of fire is higher than most 4s (16.8v) Stampedes I have seen with a similar spring load (I am approaching 10-11kg).

Edited by azrael, 27 August 2013 - 11:53 AM.

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#24 Hammy

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Posted 27 August 2013 - 10:26 PM

I have seen trustfires overheat and melt the shell, or set the battery holder on fire.

Anyway if using a higher voltage andd higher current source, then a connection using insulated copper based connectors is always best.
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#25 azrael

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Posted 28 August 2013 - 01:32 AM

The issue is the spring, just don't use the stupid battery tray contacts hahaha. That's all it comes down to.
Or at least solder to the metal plate and not the spring. Or solder a crap load of wire or something to the spring to increase the area. That will reduce resistance.

As far as trustfires doing that, I would say that's more due to overdischarging the cell or shorting the battery. Trustfires have terrible current discharge rates. Well below what most powerful motors need at stall. When using any kind of powerful battery, you should always install a simple LED voltmeter to prevent overdischarge.

Edited by azrael, 28 August 2013 - 01:35 AM.

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