Wiring Question for Home-Built Box

[apache1649]

I am planning on building an unregulated, MOSFET'ed box. My question is, if I wire 2 LG HB6 batteries in parallel to achieve a 60A continuous discharge at 3000mAh, could I wire a single, lower-amperage battery with 3000mAh to that assembly in series to increase voltage? I've read that I need at least 5v to make the MOSFET work, which I can't achieve with the 4.2 that the batteries charge to, and I want it to be small enough to fit in my pocket. If I have to I can simply make it bigger and do 2S2P and not carry it around with me, but if 1S2P is plausible then I would rather do that. Basically I'm trying to get 3000mAh 60A with a MOSFET with 3 batteries. Any and all help/advice is much appreciated, and if any or all of what I said is just 100% purely wrong I will take no offense to being corrected on every point.

- Nick

 

[SupplyDaddy]

What mosfet are you using that Has to have 5v to work? I have the IRLB3034PBF N-CH Mosfet, as well as others, that work perfectly fine in the 3+ volt range.

 

[apache1649]

I haven't ordered one yet, but reading over electronics articles and forums it seemed that there was a 5v minimum on some, and a 10v minimum on others. That actually makes it a lot easier, because I'll just wire 3 or 4 in parallel to make 90-120A continuous output and 4500-6000mAh, right? Also, I read something about wiring 2 MOSFETs in series to reduce heat, is that something I should do? And is it safe to use a different cell wired in series with a parallel pack of cells? Just for future reference.

Thanks,
- Nick

 

[SupplyDaddy]

The mosfet in my previous post is the most popular, most used, N channel mosfet around. If you're going to use 2 mosfets, you do so in parallel (same direction, same legs soldered together, along with a single 15k (most suggested) resistor. And it's not going to do too much for you anyway unless you're going to try to go below .2 ohms, and even then it may not do much for you.

Your batteries should all be matched. Same type, same age, same usage. To do otherwise invites battery failure, and it might not be pretty!

 

[apache1649]

I will most definitely be building below .2 ohms, that's actually the reason I want to build this box, is because I don't want to blow up a battery trying to vape at .7 or so on a single 18650.

-Nick

 

[apache1649]

.07*

 

[93gc40]

For .07 I would be looking at 4 batteries in parallel or stepping up to 26xxx. 3 will work. IDK, about series, I'd think you'd be looking at a 6-8 battery circuit, for it to be safe to vape.

 

[apache1649]

3 batteries rated for 30 amps in parallel would be 90 amps, 4.2/90=0.0467<.07 so it should be fine with LG HB6 batteries. 4.2/.07=60.0 so it falls well within the rating. I've decided to go with that.

 

[93gc40]

https://www.e-cigarette-forum.com/f...-test-results-better-than-sx30-at-25a.682205/

if you hadn't already seen this.

 

[apache1649]

Yeah, I've seen a few places saying they don't perform as well as other batteries below 20-25 amps, but I have 3 Samsung 25Rs that I'll be using for my higher ohm builds. The HB6s are for my super sub-ohm builds, like dual nichrome staple variants. The ones I've built usually run between .05 and .09 so I haven't had a device that I can test them with. Especially considering my only mod right now is my flip, and there is no way that I'm letting that get damaged.

 

[apache1649]

If you're going to use 2 mosfets, you do so in parallel (same direction, same legs soldered together, along with a single 15k (most suggested) resistor.

Do I put the resistor before or after the mosfets? And should the mosfets be placed back to back, or in the same direction?

 

[Nightly_Paradox]

On top, one leg gets soldered to the mosfet gate, and the other gets soldered to the mosfet source pin.

Sent from my Nexus 5 using Tapatalk

Edited: for spelling