When do you need a MOSFET?

[bitofanidiot42]

Is there any sort of battery output number where getting a MOSFET is probably right. (This isn’t currently a problem for me, I’m just wondering).

 

[Adolf Hamster]

depends on what you're getting the mosfet for.

if it's just a basic unit for protecting contacts, then whilst any battery will eventually carbon them up the higher discharge stuff especially 11.1v li-po will drastically shorten the lifespan without a mosfet.

if you're looking at more advanced units (warfet/ab++, titan etc) then the driving factor is additional functionality rather than strictly battery choice.

 

[RostokMcSpoons]

View attachment 91635

(Allegedly!)

 

[bitofanidiot42]

Ah ok, so running my 11.1 lipo is not recommended, does it even bring any benefits? From what I’ve seen it only increases rpm.

I’ve just searched up titan MOSFET and it’s something you can program, what does that do?

 

[Adolf Hamster]

Ah ok, so running my 11.1 lipo is not recommended, does it even bring any benefits? From what I’ve seen it only increases rpm.

not recommended isn't strictly the whole story.

it'll increase your rate of fire/cycle time (aka "trigger response") on a given setup, and for mostly stock guns it's an effective way of boosting the system without splashing out on aftermarket motors.

the trigger contacts thing is an issue, but unless you're running a less common gun with proprietary trigger parts it's not so big a deal to have to change out a set of contacts if they burn out.

generally speaking if you're building the gun (ie changing all the things) then you build to the battery you're using, which often means 7.4 when combined with typical motor/gear combos.

the mosfets to avoid are the ones that only offer active breaking without any precocking functionality, as outside of some specific cases applying active brake to a build that doesn't need it (ie a sane and sensible build) can cause issues with the system stopping too quickly and locking up on semi-auto.

 

[Rogerborg]

Ah ok, so running my 11.1 lipo is not recommended, does it even bring any benefits? From what I’ve seen it only increases rpm.

And semi-auto trigger response.  When paired with a motor that can use the extra volts (and current from a higher capacity x C battery) the difference can be startling.

It will increase trigger contact arcing, and you might experience double-shots on semi where the motor keeps running after you release the trigger.  That's what an active brake / pre-cock mosfet can help with.  As Adolf said, if that's what you're using it for, you'll want a programmable one.

The Perun AB++ is a pretty good value (by airsoft standards) mosfet that provides a decent amount of programmable features.  If you want to splash out even more, the Perun Hybrids or Gate Aster (or the older Titan) optical mosfets completely replace the trigger contacts and can allow for real hair-trigger wankergun builds.

If you're only interested in trigger protection, then the very cheapest mosfets will do that, and given that trigger contacts cost £5 there's little point in spending more than you have to.

Bear in mind that adding any trick electronics will introduce another point of potential failure.  I'd always recommend having one dumb, unmeddled-with backup AEG before upgrading / "upgrading" your main one.

 

[Sneaky]

Depending on the mosfet, you’d an use any battery you like….but take into consideration your AEG first. I run a 11.1v in my sr25, which my back up is a 7.4v.  I have not noticed any difference in performance. 
 

But saying that I would not put my 11.1v battery into my TM SCAR, which is upgraded, but runs nicely on a 7.4.

 

[Speedbird_666]

 and given that trigger contacts cost £5 there's little point in spending more than you have to.

Except when the trigger switch assembly is proprietary and nowhere in the UK stocks them.....I've just found that one out the hard way....?

Sooo...a cheap (non-AB) mosfet will be going into my particular gun, just so I don't have to order replacement trigger contacts from the US or HK later on.

Oh - this is after 30mins of gameplay on an 11.1v LiPo with said gun:

View attachment 91615View attachment 91614

 

[Adolf Hamster]

Except when the trigger switch assembly is proprietary and nowhere in the UK stocks them.....I've just found that one out the hard way....?

i feel ye man, exact same story with me g&g f2000, had to order from evike......

 

[Ussli]

Usually mosfet selection of 7.4V is the best choice. In semi-automatic mode it can meet the demand. 11.1V will bring high ROF in full automatic mode, but will bring higher current shock to the mos tube. Most of the damage to the mosfet is that the mos tube is burnt and difficult to repair. As for the microswitches/optics. . . There are pros and cons to each switch. Novices are advised to choose a micro switch, which is easy to install and maintain, and the cost is relatively low.

 

[bitofanidiot42]

Thanks a lot guys…

This is probably a bit of a dumb question but could you “half-charge” an 11.1V? With my 11.1 toy electric car, the power gradually decreases until it barely moves.

So, could you just have it on a lower power?

 

[EDcase]

Not really.  One of the benefits of LiPos is they try to deliver constant current (power) right up to the end (though you shouldn't let them get to the point they quit)

If your toy car performance slowly dies it probably means the battery is not very healthy or just not very good quality.

 

[Dan Robinson]

Beaten to it..... 

But i was about to say thats not how batteries work. 

I just had a mosfet fitted to my boy's M16 as it had carbon build up after 6 or 7 game days.  Hes using a 9.6v NIMH though. 

 

[bitofanidiot42]

It turns out that my car battery is a ‘1800 mah’, ‘Ni-Mh’, and a ‘7.2 VOLT POWER PACK’. 
Suitable for a gun?

It seems to be two sticks joined in a plastic shell

View attachment 92098

 

[Dan Robinson]

I'd say it would be a bit anaemic. 

 

[bitofanidiot42]

I'd say it would be a bit anaemic. 

I also have one with 3000 mah

 

[Shamal]

3000 mah will give a good run time but nimh may lack the oomph needed quickly.

 

[bitofanidiot42]

3000 mah will give a good run time but nimh may lack the oomph needed quickly.

So let’s say I’m planning to get a JG T3. The only thing is that it shoots 370 where I need to get it down to sub 350.

Would using a weaker battery do the same as a spring downgrade or is this lipo ‘oomph’ the fire-rate?

 

[Dan Robinson]

Your mah give you capacity/longevity, but the volts give you the oomph. 

I use 7.4v lipo's that i got for my drone with 2700mah.  One lasts a full day with just about 50% used up. 

This is measured by the charger as it charges and discharges (for storage) and knowing this helps keep track of battery health. 

Also worth ditching mini tamiya connectors as well. 

I also bought some 1300mah lipo's that should fit in my stick extension if it ever becomes stocked anywhere in the civilised world.   I ran with one to tty it out and it got me about two thirds of a game day. 

Annoyingly the 2700mah doesn't fit so i havr it strapped to the underside of the stock.  Looks a bit cyberpunk LOL

Lipo give you more consistent voltage through the discharge, and a much higher power density. At the expense of volatility. 

NIMH being old chemistry, are much safer, and can be left fully charged for ages.  Lipo's need to be stored at a specific voltage if not being used for more than a few days.  Hence the need for a decent charger. 

 

[bitofanidiot42]

So 7.2 Nimh would give lower fps than a 7.2 lipo?