Friday, September 20, 2013

The Truth Behind Trustfires

It seems that one of the most heavily debated questions among the Nerf community is: can Trustfires be used for mods?

The short answer is: yes. The Pros and Cons of Trustfires are listed below.

Pros:
  • Fits AA battery holders
  • Very cheap
  • Easy to mod
  • Limited current output (2.5C max. cont. => 2.25 A max. cont. current, 4.5 A max. burst current)
Cons:
  • Limited current output (2.5C max. cont. => 2.25 A max. cont. current, 4.5 A max. burst current)
  • Low Capacity (900 mAh)
First of all, you may have noticed that limited current output is listed in both the Pros and Cons list. I assure you that this is not a mistake. The biggest and perhaps only argument that people have against using Trustfires is the fact that they cannot supply no where near the amount of current even stock motors need at common modded voltages. I have a degree in electrical engineering and I can assure you that using Trustfires as the power supply for any Nerf application that involves propelling darts is terrible engineering. In fact, I wrote a guide on how to properly pair a battery to a motor, or vice versa.

FB1: How to select an electrical power system: motor and battery

Now I could bore you with a bunch of facts and logic (sort of what the above linked guide is composed of), but suffice it to say that Trustfires are not made for high power applications, and shooting darts at the range you want is. Engineering-wise, stressing a component beyond its specified limits is bad. In the real world, this only becomes a problem if undesirable effects are seen. To my knowledge, I have never heard of anyone's Trustfires blowing up or catching fire or even leaking due to abusing them in their Nerf blasters. In addition, because Trustfires are current limited, they do not trigger the thermoresists (based on my testings, may trigger in a hot day). I slapped in 3 Trustfires into a Rapidstrike for the luls and it fired beautifully. When I switched them for a 3s LiPo, the thermoresists got trigger after only a few shots. Having to be able to leave the thermoresists in the blaster is safer, especially for the audience that Trustfires attract (noobs). In addition, since Nerf flywheel systems are not "torque" limited at no load, high RPMs, a trustfire system can project a dart nearly as far as a system with a proper battery. This means that the benefits of over-volting still applies as long as the motors at no load (revved but not shooting darts) do not pull more than the Trustfires' maximum continuous discharge current (2.25 A for a single/in series 14500, 900 mAh cell/cells). The spin-up/recovery time is the only real performance factor that suffers from using a current limited battery. However, this does not mean that you should push the voltage as high as possible. Higher voltages mean higher no load currents as well as increased spin-up/recovery times.

In the end, Trustfires are no where near the ideal battery for Nerf power applications. However, its near "drop-in and shoot" ability makes it a very compelling mod for those who do not have the time/technical expertise/tools/money/patience to carryout a real, proper mod to their blaster.

18 comments:

  1. This comment has been removed by the author.

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  2. IMR, or "safe-chemistry" Li-Mn, batteries make Trustfires pretty much obsolete for NERF modifications. They are similar to Trustfires, but safer (they are more resilient to over charging/discharging and there are less unsafe fakes around) and commonly capable of up to 10A continuous discharge.

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    1. I have heard of IMRs like that or LIFePo, but never got around to buying or testing them. We are aware of their existence, but Trustfires are very popular in Nerf, and have been for years - we have our Rayven article which recommends different types, but this article was written to address the current popularity of Trustfire batteries.

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    2. Yes, someone else mentioned this. They offer a better discharge rate as well as being very safe, with the only downside of being a little more expensive. Still I think IMR batteries are the way to go for those that are compelled by the trustfire mods.

      We will look into this battery soon and post our findings :D Thx for the info though :)

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    3. The best thing is IMRs can be charged with standard Trustfire chargers. This makes them a good choice for people who currently use Trustfires but want something better and don't want to buy a whole new charger for LiPo or LiFe packs. They come in all the standard sizes too. :D

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    4. While you say Trustfires are "obsolete", I have never seen anyone using these IMR batteries. Where exactly are they popular, within Nerf?

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    5. I suppose I should really have added 'will' to that sentence (although they are already completely obsolete in the UK).

      Everyone at BritNerf now uses IMRs in place of Trustfires and anyone suggesting using Trustfires is advised otherwise (due to their unsuitability to meet our demands and the fact that many of the Trustfires coming into the UK are unsafe fakes). AFAIK, the first known use of IMRs for NERF was on BritNerf and, because it wasn't that long ago, it's taking time for the use of IMRs to become more common across the pond.

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    6. Interesting, I just recently joined BritNerf. On American NIC forums, everyone is very defensive about Trustfires, and refuse to see the actual limitations of their design.
      That's great, most people on American NIC forums are hesitant to even consider limitations of Trustfires.
      Need to get some IMRs for testing, pretty neat. Infamous and I just use LiPos because its what we have always used in our robotics projects, and they still have the lowest internal resistance and best current density of batteries.

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    7. Yeah I noticed that. Even though they usually have a continuous current rating between 10-16A, and can be used with existing Trustfire chargers, people still refuse to give them up. It's a similar problem with most modders calling any weird or new electronic component that they find inside a blaster a "resistor" even if the PCB tells them otherwise. :P

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  3. This comment has been removed by the author.

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  4. i wanna start by letting you know i really love this blog, explaining the science behind the mods is a very great idea in my opinion. ive had friends ask me why im doing what im and my only response is "because".

    i am almost completely ignorant to anything electrical, but i noticed you specifically call out the flywheel blasters. does this still apply to blasters like the dart-tag swarmfire?

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    1. for some reason I never saw this comment, I apologize. I love the swarmfire! It's one of the "stock" level blasters I bring to NiC level wars that usually have homemade blasters.

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  5. I know this thread is old but I have some questions. Why have we not gone to 18650 batteries?

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    1. Well, "we" is relative, right? Many people still prefer Trustfires because it's what they first used, and because it's cheap.
      There are users out there with 18650s.
      I have a couple *fires and AA sized IMRs, but most of my blasters use LiPo power packs when possible. Which have even greater current capacity than 18650s.

      torukmakto4 is a user who welds his own 18650 battery packs together with great success.

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  6. Do you know a good place to get IMRs or Trustfires because I can't find any brand that consistently gets good reviews.

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  7. Why not just put a set of 4x or 6x trustfires/IMR in parallel to give you more output or perhaps get a small capacitor?

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    1. If you need more current, IMO, it's better to go with a better battery chemistry. The price point is probably the same, considering Trustfires have a relatively low C rating.

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