m4 acting like battery dies

[Kos-Mos]

Originally Posted by MaciekA

Interesting ideas.

I wonder where the heat is causing the power drop though, since the Curie temperature for rare earth magnets is extraordinarily high (even neo magnets for example, which have among the lowest Curie temperature, don't start to lose magnetism until they're between 300-400 Celcius). For airsoft applications, these would be very high temperatures. Do you think it's in the wiring somewhere maybe?

Also, I like theory #2, mainly because I've seen so many weak-sauce batteries out there. One way to be sure is get a nice big R/C battery with a high C value, say, 7.4V 5000mAh and 40C, and hook it up to this gun. The problem though, is that it might mask another issue by powering through whatever real problem lies beneath.

edit: Just noticed you suggested the same thing. Shame on me for not reading your whole reply.

I have seen cheap neodymium magnets losing magnetic field around 200-ish C... especially in cheap Chinese brushed motors (in RC cars). Once the process is started, it just goes exponential (motor has less torque, but the load stays the same, so more current has to flow, resulting in more heat and less torque...).

To feel the grip getting hot, the motor core would be close to 200-ish...

[m102404]

Originally Posted by MaciekA

Interesting ideas.

I wonder where the heat is causing the power drop though, since the Curie temperature for rare earth magnets is extraordinarily high (even neo magnets for example, which have among the lowest Curie temperature, don't start to lose magnetism until they're between 300-400 Celcius). For airsoft applications, these would be very high temperatures. Do you think it's in the wiring somewhere maybe?

Also, I like theory #2, mainly because I've seen so many weak-sauce batteries out there. One way to be sure is get a nice big R/C battery with a high C value, say, 7.4V 5000mAh and 40C, and hook it up to this gun. The problem though, is that it might mask another issue by powering through whatever real problem lies beneath.

edit: Just noticed you suggested the same thing. Shame on me for not reading your whole reply.

Tsk, tsk...shame...LOL JK.

I've had more than a few motors over the years come across the bench that seemed ok, but just didn't handle as expected under load. (IMO)...once a motor is heated past it's operating thresholds it is weakend and needs to "work harder", requiring more power, than before to accomplish the same tasks. This further tasks and compounds issues with a marginal system. Simplest thing to do is to just pin it down to the motor and chuck it.

I've also had the odd motor that seemed to work sort of...but couldn't sustain long strings of shots (in multiple setups/batteries). I suspect that it had to do with a fault in the motor that worked when it was cooled and then failed as the wiring heated. Those would just stop dead though and not slow down as described.

Re. just putting a "BIG" battery to it...yes, I think that it would really only serve to mask other issues. Unless you're running a very powerful setup you shouldn't need more than a regular large battery to cycle a mechbox.

Re. wiring...yes certainly. Some setups have come across the bench with poor joints/splices that just starved off the motor. I think the record I've seen was one that had 7 splices in one wire...and only 2 were soldered!!! Kinks/nicks/pinches/shitty wiring will starve the system. Poorly attached connectors, poorly done splices and poor soldering jobs at the switch will do the same. Wire that is tired should be replaced...the wire is probably oxidized/corroded in it's sheathing. Connectors need to all be soldered...splices should be avoided...all wiring should be insulated...all solder joints should be able to withstand a tug just shy of hard enough to bend/break what it's attached to. Wiring should be a MINIMUM of 18AWG solid strand (not solid core, but it should not be braided) copper wire...or good quality high efficiency "silver" wire (warning...there's crappy "clone" silver wire out there). If find the silver wire to be a pain sometimes with soldering...and actually prefer copper wire. The thing "standard" wiring used in so many AEGs was ok (not nice, but ok) for old stock guns when you were pushing m90/100 stock springs with a 8.4v mini....that's not the stock builds now but the wiring hasn't changed. ACM type companies just shitty solder too and it's not uncommon to have wiring simply pull off the switch tabs once you're into the mech.

[MaciekA]

Originally Posted by Kos-Mos

I have seen cheap neodymium magnets losing magnetic field around 200-ish C... especially in cheap Chinese brushed motors (in RC cars). Once the process is started, it just goes exponential (motor has less torque, but the load stays the same, so more current has to flow, resulting in more heat and less torque...).

To feel the grip getting hot, the motor core would be close to 200-ish...

Wow, crazy. The exponential rise in temperature is really interesting, kind of like a vicious cycle. In a sufficiently-large R/C car I could imagine there being a few options for introducing a cooling system. I can't quite imagine what we would need to cool an airsoft motor in-situ. A grip designed hand-in-hand with a motor housing, with the housing having a dense array of fins. The question becomes.. where to dump that heat?

I have noticed fairly huge differences in heat output from different neo motors which pretty much have the same magnetic stickiness and torque when tested "in the lab". My JG Blue hardly produces any heat at all, while at the same time the SHS High Torque seems to get fairly warm -- but only the long version, where as the short version doesn't produce much heat.

I've gotten the impression, but haven't been able to solidly verify, that some motors seem to produce less heat if they've powered by a larger battery with a higher C value. I'd love to hear someone explain why the heck that would happen.

[ThunderCactus]

my EF1300 produces very little heat. Until I start laying down the hate, after half a box it feels like my grip is gonna melt lol
The impressive part is it doesn't lose any power at that temp

[Styrak]

Originally Posted by MaciekA

I've gotten the impression, but haven't been able to solidly verify, that some motors seem to produce less heat if they've powered by a larger battery with a higher C value. I'd love to hear someone explain why the heck that would happen.

Because the battery and motor don't have to work as hard. Think about it like this, if you had to move a huge rock and had a 2 inch long stick as a lever (mini cell battery), you'd have to work REALLY hard to move it. If you had a 4 foot long stick as a lever (large cell battery) it wouldn't take any effort at all.

The power gain in large batteries vs mini batteries even in the same voltage is huge. Not to mention the internal resistance differences and probably a couple other differences.

[Kos-Mos]

Originally Posted by MaciekA

Wow, crazy. The exponential rise in temperature is really interesting, kind of like a vicious cycle. In a sufficiently-large R/C car I could imagine there being a few options for introducing a cooling system. I can't quite imagine what we would need to cool an airsoft motor in-situ. A grip designed hand-in-hand with a motor housing, with the housing having a dense array of fins. The question becomes.. where to dump that heat?

I have noticed fairly huge differences in heat output from different neo motors which pretty much have the same magnetic stickiness and torque when tested "in the lab". My JG Blue hardly produces any heat at all, while at the same time the SHS High Torque seems to get fairly warm -- but only the long version, where as the short version doesn't produce much heat.

I've gotten the impression, but haven't been able to solidly verify, that some motors seem to produce less heat if they've powered by a larger battery with a higher C value. I'd love to hear someone explain why the heck that would happen.

Physics 101...

Electro-magnet coils produce a magnetic field proportional to the CURRENT flowing through and the number of turns. (Higher number of turns = higher resistance = lower current).

Current is measured instantly. That is why batteries are rated in mAh or milliamps-hours, the the amount of current that can be sustained for 1h before the pack is empty.

The rate (or C) of a battery is the maximum current it can give. For example, a 1400mAh NiMh 2/3A battery (mini packs) can deliver around 10C, so roughly 14A at MAX.

A better battery for example a 4500mAh NiMh Sub-C (large packs) can deliver around 10C also (limited by the chemistry), roughly 45A at MAX.

Given both packs are 8.4v, the same mechbox and motor, the magnetic field of the motor running on the larger pack will be more than 4 times stronger. That directly results in more TORQUE.

The problem when a motor struggle to accelerate is that it will ask for that MAX current for a longer period of time. The curve of required current vs. speed is logarithmic (starts at +infinity, dropping VERY fast to almost nothing), so if you prevent the motor from accelerating by starving it, it will generate more heat for a longer period (we talk milliseconds, but the "cycle" only lasts a few hundread milliseconds anyways).

So the larger the battery, the better. Contrary to what youtube seems to say, running your AEG on a car battery won't break it any faster than running it on a 11.1v LiPo. In fact, the car battery will put a lot less stress on your motor.

[MaciekA]

Originally Posted by Kos-Mos

Physics 101...

Electro-magnet coils produce a magnetic field proportional to the CURRENT flowing through and the number of turns. (Higher number of turns = higher resistance = lower current).

Current is measured instantly. That is why batteries are rated in mAh or milliamps-hours, the the amount of current that can be sustained for 1h before the pack is empty.

The rate (or C) of a battery is the maximum current it can give. For example, a 1400mAh NiMh 2/3A battery (mini packs) can deliver around 10C, so roughly 14A at MAX.

A better battery for example a 4500mAh NiMh Sub-C (large packs) can deliver around 10C also (limited by the chemistry), roughly 45A at MAX.

Given both packs are 8.4v, the same mechbox and motor, the magnetic field of the motor running on the larger pack will be more than 4 times stronger. That directly results in more TORQUE.

The problem when a motor struggle to accelerate is that it will ask for that MAX current for a longer period of time. The curve of required current vs. speed is logarithmic (starts at +infinity, dropping VERY fast to almost nothing), so if you prevent the motor from accelerating by starving it, it will generate more heat for a longer period (we talk milliseconds, but the "cycle" only lasts a few hundread milliseconds anyways).

So the larger the battery, the better. Contrary to what youtube seems to say, running your AEG on a car battery won't break it any faster than running it on a 11.1v LiPo. In fact, the car battery will put a lot less stress on your motor.

Thanks for the awesome explanation. This backs up many observations I've made over the last year but couldn't explain with my weak knowledge of the physics involved.

For what it's worth, I've got a ZIPPY brand battery coming in from Hobby King this week that's 7.4V, 6000mAh and 35C. Should push everything in my stable pretty effortlessly, though it's fairly certain none of my motors will be asking for anything close to 210A

[Renegade)]

Man some very good, detailed answers here...

Short and simple dude, your battery and/or motor cant handle your current "custom" set up. Motor and Gears cant handle the spring. If shimming was too tight, it wouldnt shoot semi very well either, and you said it works fine with that. Not to mention it would sound terrible and be putting even more stress on your motor.

[MaciekA]

Originally Posted by Renegade)

Man some very good, detailed answers here...

Short and simple dude, your battery and/or motor cant handle your current "custom" set up. Motor and Gears cant handle the spring. If shimming was too tight, it wouldnt shoot semi very well either, and you said it works fine with that. Not to mention it would sound terrible and be putting even more stress on your motor.

Well said. Fix up that shimming and follow my golden mantra: MORE POWER

[Styrak]

Originally Posted by MaciekA

Well said. Fix up that shimming and follow my golden mantra: MORE POWER

Yup, you should always use the biggest damn battery you can stuff into your gun. If your gun only fits minis you may want to think about using a PEQ/battery box or battery bag with a large. Even an 8.4v large is a ton of power that should run almost anything up to 450-500fps.

[Visser]

So I got a large battery and it seems to be working great now. I'd like to see him game it and then say but we got rained out here this weekend. Thanks for the great info everyone.

[Renegade)]

Originally Posted by Styrak

Yup, you should always use the biggest damn battery you can stuff into your gun. If your gun only fits minis you may want to think about using a PEQ/battery box or battery bag with a large. Even an 8.4v large is a ton of power that should run almost anything up to 450-500fps.

Yeah! If it doesnt fit, make it fit

[MaciekA]

Tamiya connector? Heresy!

[Renegade)]

Originally Posted by MaciekA

Tamiya connector? Heresy!

Old pic, its Deans now of course.

[MaciekA]

Deans connector? Heresy!