My Mosfet/Wiring Upgrade

[Pointy]

Have a stock E&C K18 MOD 1 and will be installing a MOSFET and wiring upgrade.

Creating this thread for Q&As around my upgrade, and record the progress.

Below is the schematic and BOM I have put together from various sources on the web. Nothing fancy and no active braking.



Please comment on the schematic, let me know if you see any issue.

With the higher current capacity of LiPo batteries, is a capacitor bank worth while?

FYI - Battery is wired to the rear.

[Kos-Mos]

Cap banks are not worth it in airsoft guns, so you can remove that.

Also, space is very limited most of the time. You are better use a 10% larger LiPo that fit tight than leave space for some caps.

For your wires, I would save the 22ga and get that locally.
In fact, I used some 26ga I got for 0.05$/feet in my local surplus store. Just get something that is not solid, it might break.

[Pointy]

Originally Posted by Kos-Mos

Cap banks are not worth it in airsoft guns, so you can remove that.

Also, space is very limited most of the time. You are better use a 10% larger LiPo that fit tight than leave space for some caps.

For your wires, I would save the 22ga and get that locally.
In fact, I used some 26ga I got for 0.05$/feet in my local surplus store. Just get something that is not solid, it might break.

Thanks, I'll get rid of the caps.

Thinking of changing to a 11.1V LiPo battery 20-25C, just need to figure out one that will fit into my stock. The 7.4V LiPo I have now is 100 x 19 x 12mm; think I have limited space to increase the width and height, but can increase the length.

[Stealth]

Where do you plan on storing the FET itself?

[Pointy]

Originally Posted by Stealth

Where do you plan on storing the FET itself?

My thought is to place the FET unit down one of the battery compartment sides on the stock.

This would leave the buffer tube, and the other side of the stock for a battery.

Looking at Turnigy nano-tech 1200mAh 3S 25-50C Lipo AIRSOFT Pack. I need to do some measuring tonight, but I think either all three in one of the stock compartments, or two in the stock, one in the buffer tube.

Another opinion is Turnigy nano-tech 2000mah 3S 15~25C Lipo AIRSOFT Pack but I am thinking they might be too large.

FYI - I always have the stock, fully extended.

[K3vX]

Subscribing to this thread, because I'm in the exact process of building my own mosfet :P

One thing I'd like to know, is the software you used to create the diagram? Everyone that I use online is either crappy or crazy expensive.

[Pointy]

Originally Posted by K3vX

Subscribing to this thread, because I'm in the exact process of building my own mosfet :P

One thing I'd like to know, is the software you used to create the diagram? Everyone that I use online is either crappy or crazy expensive.

I use MS Visio 2010 - Get a very good deal via my company (was like $20).

[ThunderCactus]

I have to ask
What's your reason to building your own as opposed to buying a manufactured mosfet?

[K3vX]

Originally Posted by ThunderCactus

I have to ask
What's your reason to building your own as opposed to buying a manufactured mosfet?

It's fun? That's my reason.

Also, cheap (As mentioned below)

[Kos-Mos]

I will assume that you have an M4-type gun with a Crane stock or similar.

You should be able to fit a 1200mAh pack inside the buffer tube completely, with maybe room for the FET depending on the brand of your gun/stock.

For the 2000mAh pack you linked, I doubt it will fit, and if it does, it will be 1 stick in each compartment. If you have a crane stock that can fit sub-c cells, I would recommend you to go the NiMh way instead. A good quality 9.6 or 10.4v 5000mAh pack will deliver 35C and give you a lot more capacity. They are heavier however.

[Kos-Mos]

Originally Posted by ThunderCactus

I have to ask
What's your reason to building your own as opposed to buying a manufactured mosfet?

I build mine because it's a LOT cheaper than any "basic" model available and a lot more powerful.

It cost me 4$ all-in and the FETs I use are rated 240A constant.

[Pointy]

Originally Posted by ThunderCactus

I have to ask
What's your reason to building your own as opposed to buying a manufactured mosfet?

Mostly because it is cheaper to DIY, and I dont want/need the features most commercial MOSFET units have like Active Braking, 3-round bursts etc.

[Pointy]

Originally Posted by Kos-Mos

I will assume that you have an M4-type gun with a Crane stock or similar.

You should be able to fit a 1200mAh pack inside the buffer tube completely, with maybe room for the FET depending on the brand of your gun/stock.

For the 2000mAh pack you linked, I doubt it will fit, and if it does, it will be 1 stick in each compartment. If you have a crane stock that can fit sub-c cells, I would recommend you to go the NiMh way instead. A good quality 9.6 or 10.4v 5000mAh pack will deliver 35C and give you a lot more capacity. They are heavier however.

Yes it is a M4 with a collapsible stock. See me original post for a link to the gun.

Another possible battery pack- http://www.hobbyking.com/hobbyking/s...SOFT_Pack.html

From another forum it was mentioned this would fit in the buffer tube with the stock 1 click out. I always run the stock fully extended, as I have long arms.

Curious about your recommendation to use NiMH; LiPo seems to be a very popular choice.

[K3vX]

NiMH can be powerful, but gram for gram LiPo is better. You need to find a LiPo worth it.

I personally don't know the Amperage of NiMH packs, so I cannot compare them. Kos-Mos seems to indicate it's good enough.

What I know is that for LiPo packs, it's the Ah rating x the C rating, so the last pack you linked, 1.2 x 25 = 30A of constant power that can be delivered. You should not need more, unless you have a high power and/or very high speed build.

Edit:

Also, the two packs that you linked that have the same mAh rating, 1200mah, are the SAME pack, except one has the cells separate, and the other one has the cells wrapped together.

[Kos-Mos]

Originally Posted by K3vX

NiMH can be powerful, but gram for gram LiPo is better. You need to find a LiPo worth it.

I personally don't know the Amperage of NiMH packs, so I cannot compare them. Kos-Mos seems to indicate it's good enough.

What I know is that for LiPo packs, it's the Ah rating x the C rating, so the last pack you linked, 1.2 x 25 = 30A of constant power that can be delivered. You should not need more, unless you have a high power and/or very high speed build.

Edit:

Also, the two packs that you linked that have the same mAh rating, 1200mah, are the SAME pack, except one has the cells separate, and the other one has the cells wrapped together.

Works basically the same, except that ratings are usually tied to the physical shape of the battery. A typical Sub-C will give 35C. That's 5000mAh x 35 = 175A instant current.