mosfet wiring question

[windxrunner]

Well, I have decided to use a mosfet. I have to make a decision on how to wire it, though.

Here's the two I'm considering.

The first has the positive going from the mosfet, to the switch(es), to the batteries, then to the atty. Like this:

The second has the positive going from the batteries to the switches, then that positive wire joins the mosfet wire coming from the gate before they both become one and go to the atty. Like this:

The second one is safer, is my first impression. what do you guys think?

 

[DaveP]

Option 1 would be my choice since it uses one battery. It needs an on-off switch.

As for option 2, I wouldn't knowingly stand close to anyone vaping with stacked batteries unless the circuit had protection against reverse charging. All it takes is one battery at low potential and the other fully charged and the higher charged battery will try to equalize the voltages by draining potential into the lowly charged battery. They heat up very quickly when that happens. All the news stories about mods that blew up used stacked batteries. 26650's can be scary when that happens and choice 2 says that there are three 26650's in parallel. That's a small welder!

You might want to look at DNA30 vape mods for some protection or engineer a high amp diode into the battery circuit for option 2 that would prevent reverse current flow by only allowing voltage to flow in one direction. Some DNA30's use two batteries and it's a tried and true design with over-current protection.

 

[Dampmaskin]

Option 1 looks best to me, because it doesn't require high current switches. With option 2, what purpose does the MOSFET serve?

 

[WKS01]

...choice 2 says that there are three 26650's in parallel. That's a small welder!

There is only one battery shown in option 2. Though I am not sure why option two is using the mosfet since the switch will still have to be able to handle the full current load.

 

[somun]

Something's not right with option 2 there. Atty's + side should not be connected through the switches but directly to the bat +. Then it becomes option 1 with an additional on/off switch (i.e. to something like a switch lock)

 

[windxrunner]

I'm not going to be stacking batteries and I'm not following the battery suggestions in the 2nd one, lol. I'm just looking at the way they drew the wiring.

So option 1, then? Thanks, guys.

 

[windxrunner]

Where would you guys put the on/off switch? I want to use one.

(oh and btw, I'm going to be using two batteries, but in parallel. I've got two brand new VTC4's I'm going to essentially marry and use only for this vape mod)

 

[somun]

You can put the on off switch in series with the push button.

 

[windxrunner]

ok, that's what I figured. but does it matter if it's between the mosfet and the push button or between the push button and the battery?

 

[AzPlumber]

The master switch on pos. side before any other connections. You can make your connections for the fire switch and atty at the master switch.

eta: use the first drawing.

 

[windxrunner]

thank you.

 

[AzPlumber]

I know everyone thinks parallel is safer than series but I would still fuse each battery. If not fused and one battery fails the other will take the full load. If your counting on the batteries to split the current load this will go bad quickly. On top of that the good battery will be pushing current into the failed battery.

 

[Dampmaskin]

The master switch on pos. side before any other connections.

Agreed, the master switch should be connected directly to the battery +.

Remember to use a relatively high current master switch, although arcing shouldn't be a problem as long as you don't operate the master switch while the MOSFET is open.

ETA:

I'm thinking something like this ought to work:


And be aware of grounding. If you're building in a metal box, the 510 will probably be grounded via the chassis. In that case, also grounding the MOSFET to the chassis would be a bad idea (at least with the diagram in this post).

 

[windxrunner]

gotcha. so you're suggesting I don't ground the mosfet to the negative side of the battery, but letting the 510 touch metal is cool. right? why is that? all the diagrams I've seen have the drain going to the ground on the 510 and the source going to the negative side of the battery, why is your diagram different? i just really want to understand this and I want to wire this box the best way possible.

i plan on using a 10-16 amp switch. while that is the AC rating, that should be high enough, especially when wired correctly, yes?

 

[windxrunner]

until that other diagram that didn't ground the drain, only the source, showed up and confused me, this is how I was going to be wiring it. now i'm not so sure, and pretty confused. (yes, I just made this in paint.)

red is live, blue is negative, green is a 15k resistor.

 

[windxrunner]

but the part i really want to know about is how i'm connecting the batteries. is it ok to solder a wire between the two positive connections, then connect the wire coming from the switches to one and then connect the atty to the other?

if not, how would i go about doing that?

 

[somun]

Agreed, the master switch should be connected directly to the battery +.

Remember to use a relatively high current master switch, although arcing shouldn't be a problem as long as you don't operate the master switch while the MOSFET is open.

ETA:

I'm thinking something like this ought to work:
View attachment 374773

And be aware of grounding. If you're building in a metal box, the 510 will probably be grounded via the chassis. In that case, also grounding the MOSFET to the chassis would be a bad idea (at least with the diagram in this post).

I don't think that diagram is correct. It would not work properly. N Mosfet should be used as a low side switch.

Besides it defeats the purpose to introduce yet another high current switch in the mix.

 

[windxrunner]

alright i'm less confused now. those were my same thoughts.

 

[windxrunner]

can you answer my question about the way i'm going to be wiring the batteries together?

 

[somun]

Yes you can technically connect the batteries that way but please be aware that the mosfet does not protect you from putting the batteries in reverse order which would create a direct short between them, quite possibly causing catastrophic failure. I would suggest that you consider using fuses. I believe there's a sticky thread right here about fuses.