gfxgfx
 
Please login or register.

Login with username, password and session length
logo
 
gfx gfx
gfx
19698 Posts in 1260 Topics by 5034 Members - Latest Member: Henriques11 November 23, 2017, 06:52:14 PM
*
gfx* Home | Help | Login | Register | gfx
gfx
Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: Unregulated mod and voltage drop question
gfx
gfxgfx
 

Author Topic: Unregulated mod and voltage drop question  (Read 32883 times)

0 Members and 1 Guest are viewing this topic.

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Unregulated mod and voltage drop question
« on: June 27, 2014, 05:55:08 AM »
Hi folks.  Been working on a couple of unregulated box mods, using the Hammond 1590G and 2x18650s.  I am planning on making a series mod next, but I have just finished up with building the internals of a parallel box.

Here it is:
IMG_0287 by thejewk, on Flickr

I built it with performance in mind, and I think I have achieved what I set out for. 

Running a 0.69 ohm coil, and measuring the voltage with a multimeter at the deck posts of the atty, it's dropping 0.24V.  That's significantly better than any mech I have tried, so I am pleased with that, but I would like to compare it to the performance of other unregulated mods that people have made to see where it could be improved, or just to get a comparison.

Thanks

Offline gno3545

  • Jr. Member
  • **
  • Joined: Jun 2014
  • Location: Grapevine TX
  • Posts: 12
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #1 on: June 27, 2014, 02:13:16 PM »
That looks great...haven't built my first mod yet but I'd like to copy your's

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #2 on: June 27, 2014, 02:27:00 PM »
Go ahead, there's no secrets.  I used 14 AWG for the current carrying wire, and a mosfet to power the atty with the push button and slide switch.  The 510 is a standard 510 to 510 adapter beefed up with a bolt and some insulators rather than using the stock grommet.  Next time I will be using one of Stealthvape's new 510s, and I am thinking of getting rid of the voltmeter and mounting the switch on the top of the box.  Should give me a little more room to work with.

Offline gno3545

  • Jr. Member
  • **
  • Joined: Jun 2014
  • Location: Grapevine TX
  • Posts: 12
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #3 on: June 27, 2014, 02:52:34 PM »
I'm very new to electronics but learning fast why use a MOSFET at all?

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #4 on: June 27, 2014, 03:11:05 PM »
Because that switch is only good for about 3 amps and the slide switch for a master on/off is rated at about half an amp. They also have resistance which contributes to voltage drop. Mosfets can carry large amounts of current and have very little internal resistance which helps to make them perform well.

I simply would not try to put 20 amps or so through a switch. If it fails and fails on, you could be in trouble.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #5 on: June 27, 2014, 04:10:11 PM »
True, but you also have to carefully select your MOSFETs to get those low losses.  They can vary over a pretty wide range and some can be much more lossy than others.  The really low resistance ones have considerably less resistance than a mechanical switch and they always have that resistance.  It doesn't go up with wear like a mechanical switch.

MOSFETs still need some kind of switch to control them, but there's a range of options there.  You can use a high cycle life tactile, you can use a resistive touch sensor, or a capacitive touch senser via an MCU.  Touch sensors are great since they never wear out.  The high cycle life tactiles have greatly better longevity than than a high current switch, but even those wear out eventually.

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #6 on: June 27, 2014, 04:16:58 PM »
Yes sorry, didn't mean to imply that you could use any MOSFET.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +60/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #7 on: June 27, 2014, 04:24:48 PM »
Nice mech

wow 14ga thats a monster fer sure


Craig whats a really good mosfet for a mech and regulated series mod I know beating a dead horse,  but I know ya got it bookmarked hopefully.  lol
Solderable  :laughing2:..   If not bookmarked never mind lol Ill go hunting search, know ya said it before..

Offline gno3545

  • Jr. Member
  • **
  • Joined: Jun 2014
  • Location: Grapevine TX
  • Posts: 12
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #8 on: June 27, 2014, 06:07:47 PM »
could I just use at 10 amp. Button and no slide switch?

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #9 on: June 27, 2014, 06:35:17 PM »
Craig whats a really good mosfet for a mech and regulated series mod

This one is the best P-channel I've found.  I tend to use the P-channels for regular on/off switches, it's just easier to switch the high side than the low side;  http://www.vishay.com/docs/62860/si7157dp.pdf

Here's a really good N-channel; http://www.ti.com/lit/ds/symlink/csd17559q5.pdf

These are leadless packages so you have to make a little host board for them, but if you want the best ones, that's what you have to do.  It doesn't seem like a deal breaker to me, but it seems to be for some.  My advice is to just get used to parts like that.  All the latest and greatest parts come in a leadless package or a small leaded SMD package.  Through-hole is pretty much dead now, very few new component designs are being released in that package type.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3300
  • Karma: +784/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Unregulated mod and voltage drop question
« Reply #10 on: June 27, 2014, 06:37:28 PM »
could I just use at 10 amp. Button and no slide switch?

You have to look at the voltage rating as well. I've used buttons that are rated 3A @ 125V they can hold up to much higher amperage using 4.2V
See: http://breaktru.com/smf/index.php/topic,162.msg13234.html#msg13234

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +60/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #11 on: June 27, 2014, 07:45:21 PM »
 :thumbsup:
Sorry hijack jewk but great info for us all..

Thanks again,
I had totally forgotten that ti and vishay fet  that you recommended for mamu and her way of doing it, yeah thats doable.
http://breaktru.com/smf/index.php?topic=1015.100
 Reply #124

Making some new mods soon getting order ready, parts etc..

Gotta make a touch unit then my cloning break mods are done cept the mcu/dna, I have copper pipe & parts but a little different, 08100 w/ wood dowel,  3/4" copper pipe hybrid touch--incoming eventually lol.
« Last Edit: June 27, 2014, 07:50:48 PM by Visus »

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #12 on: June 28, 2014, 05:37:33 AM »
I welcome the hijacks visus, dialogue on these subjects is a good thing surely.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +60/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #13 on: July 02, 2014, 12:06:00 AM »
This one is the best P-channel I've found.  I tend to use the P-channels for regular on/off switches, it's just easier to switch the high side than the low side;  http://www.vishay.com/docs/62860/si7157dp.pdf

Here's a really good N-channel; http://www.ti.com/lit/ds/symlink/csd17559q5.pdf

These are leadless packages so you have to make a little host board for them, but if you want the best ones, that's what you have to do.  It doesn't seem like a deal breaker to me, but it seems to be for some.  My advice is to just get used to parts like that.  All the latest and greatest parts come in a leadless package or a small leaded SMD package.  Through-hole is pretty much dead now, very few new component designs are being released in that package type.

I am ordering some parts samples etc.  making a new mods next few months  and want to use one of the fets you listed.
What pulldown resistor would ya suggest to shut either fet down 15k sound good for both 3.7 and 7.4 or try different r starting from 1k?

I've been reading up on how to do the math and the biggest concensus is that,  breadboard it,  start from 1k -1m lol..

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #14 on: July 02, 2014, 04:27:26 AM »
15k should be good.

It's a pretty liberal thing on the pull-down or pull-up values.  You don't want to go too high or you can have issue with gate charge or gate leakage but that's like above 10 mega-Ohms.  If you go too low you can have issue with power consumption.  Generally, anything between 4.7k and 47k is fine, but that's not a hard and fast rule either.  Personally, I tend to use 10k with the single battery stuff to keep the effect of gate charge minimal (higher resistance slows the switch down), but it's not a critical thing at all.  For higher voltage you may want to use a somewhat higher resistance.

Generally you don't have to concern yourself with the dynamic MOSFET stuff for a simple power switch.  When you get into high speed switching, then all that stuff becomes considerable.  In that case, the amount of resistance involved in driving the gate becomes critical.

Offline T8ternutz

  • Full Member
  • ***
  • Joined: Nov 2013
  • Location: Florida
  • Posts: 33
  • Karma: +0/-0
Re: Unregulated mod and voltage drop question
« Reply #15 on: July 02, 2014, 03:01:48 PM »
Go ahead, there's no secrets.  I used 14 AWG for the current carrying wire, and a mosfet to power the atty with the push button and slide switch.  The 510 is a standard 510 to 510 adapter beefed up with a bolt and some insulators rather than using the stock grommet.  Next time I will be using one of Stealthvape's new 510s, and I am thinking of getting rid of the voltmeter and mounting the switch on the top of the box.  Should give me a little more room to work with.

What mosfet was used in this particular Mod??

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +60/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #16 on: July 02, 2014, 08:47:41 PM »
Woot 15k  I have a boatload of 15k resistors.






Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #17 on: July 04, 2014, 10:30:44 AM »

Offline thejewk

  • Full Member
  • ***
  • Joined: Feb 2014
  • Location: United Kingdom
  • Posts: 34
  • Karma: +6/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #18 on: July 14, 2014, 10:02:01 AM »
DSCF6875 by thejewk, on Flickr

IMG_0305[1] by thejewk, on Flickr

IMG_0306[1] by thejewk, on Flickr

Here's a couple of pics of a series build I have been making for some power vaping.  Nice and compact, with excellent performance.  Testing out a series 18650 mod takes some creativity in coil making when you are used to coiling for 4.2v or thereabouts.

Offline ballageddon

  • Newbie
  • *
  • Joined: Aug 2014
  • Location: United States
  • Posts: 1
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #19 on: August 21, 2014, 09:14:32 PM »
Hi folks.  Been working on a couple of unregulated box mods, using the Hammond 1590G and 2x18650s.  I am planning on making a series mod next, but I have just finished up with building the internals of a parallel box.

Here it is:
IMG_0287 by thejewk, on Flickr

I built it with performance in mind, and I think I have achieved what I set out for. 

Running a 0.69 ohm coil, and measuring the voltage with a multimeter at the deck posts of the atty, it's dropping 0.24V.  That's significantly better than any mech I have tried, so I am pleased with that, but I would like to compare it to the performance of other unregulated mods that people have made to see where it could be improved, or just to get a comparison.

Thanks

Can I see a schematic for this parallel build please?

Offline david4500

  • Ultra Member
  • ******
  • Joined: Mar 2014
  • Location: Illinois
  • Posts: 227
  • Karma: +50/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #20 on: August 22, 2014, 09:15:22 PM »
Can I see a schematic for this parallel build please?

drawing for a very similar mod here: http://breaktru.com/smf/index.php/topic,616.msg16713.html#msg16713

Offline doobedoobedo

  • Super Member
  • *****
  • Joined: Dec 2013
  • Location: UK
  • Posts: 165
  • Karma: +35/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #21 on: August 23, 2014, 10:50:16 AM »
I'm using two of the same mosfets in parallel for a higher amp limit. 6x750mAh LiPos in parallel gives me a a voltage drop of 0.25V with a 0.16ohm coil.

I think the only way you'll get a lower voltage drop is to parallel up the cells more and/or use an even lower Rds on fet.

Offline JUICYOHMS

  • Jr. Member
  • **
  • Joined: May 2014
  • Location: SOUTHERN OHIO
  • Posts: 13
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #22 on: August 26, 2014, 02:28:20 PM »
Not trying to threadjack, but I saw this was about unregulated boxes & was hoping I could get a helpful answer.
What's the best quality or highest amp rated pushbutton for building a Mech Box running dual 18650's in parallel? I'm wanting a button that's not too huge, but willing to look at all options and I don't wanna go over $30 though...I'll be using a 1590B, Keystone 1048 and the FDV510...I'll wanna safely vape .15 ohms which is 117 watts and 28 amps at 4.2v. and maybe lower ohms if possible.
 Please LMK of any nice buttons that can handle some high amps...
 Thanks in Advance Guys

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3300
  • Karma: +784/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Unregulated mod and voltage drop question
« Reply #23 on: August 26, 2014, 05:56:19 PM »
If you are looking for a dome type button switch THIS ONE is rated at 4A @ 48VDC which breaks down to approximately 45A @ 4.2VDC. Unfortunately the button is huge at 15.9mm diameter.

Offline SDDPhoto

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: USA
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #24 on: August 27, 2014, 08:21:58 PM »
This one is the best P-channel I've found.  I tend to use the P-channels for regular on/off switches, it's just easier to switch the high side than the low side;  http://www.vishay.com/docs/62860/si7157dp.pdf

Here's a really good N-channel; http://www.ti.com/lit/ds/symlink/csd17559q5.pdf

These are leadless packages so you have to make a little host board for them, but if you want the best ones, that's what you have to do.  It doesn't seem like a deal breaker to me, but it seems to be for some.  My advice is to just get used to parts like that.  All the latest and greatest parts come in a leadless package or a small leaded SMD package.  Through-hole is pretty much dead now, very few new component designs are being released in that package type.

Sorry to hijack the hijack but would a IRL3803PBF FET (http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=156098626&uq=635447627557460125) work for a single 18650 unregulated mod. I unfortunately don't have the ability to use the lead-less package FETs that you listed before.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #25 on: August 28, 2014, 08:28:56 PM »
Getting a "not found" on that.  Someone mentioned a TO-220 part which looks to be the best one I've seen so far in a leaded package;

http://www.nxp.com/documents/data_sheet/PSMN1R9-40PL.pdf

I looked at the other NXP parts and this one might even be better;

http://www.nxp.com/documents/data_sheet/PSMN1R1-30PL.pdf

Not sure on this one since the graduations aren't the same for the "on state versus gate-source voltage" chart.  Maybe someone with better eyes can tell for sure.

Offline hanukun

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: 49428
  • Posts: 5
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #26 on: August 29, 2014, 05:35:42 AM »
what about these mosfets from ti they look like the would work in a unregulated box

CSD17501Q5A
CSD17506Q5A
CSD17505Q5A

Offline david4500

  • Ultra Member
  • ******
  • Joined: Mar 2014
  • Location: Illinois
  • Posts: 227
  • Karma: +50/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #27 on: August 29, 2014, 08:49:13 PM »
what about these mosfets from ti they look like the would work in a unregulated box

CSD17501Q5A
CSD17506Q5A
CSD17505Q5A

Max power: 3.2 watts

Offline SDDPhoto

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: USA
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #28 on: August 30, 2014, 08:01:03 AM »
Getting a "not found" on that.

Sorry about that. This is a link to the datasheet. http://www.irf.com/product-info/datasheets/data/irl3803pbf.pdf

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #29 on: August 30, 2014, 07:36:43 PM »
what about these mosfets from ti they look like the would work in a unregulated box

CSD17501Q5A
CSD17506Q5A
CSD17505Q5A

TI makes some really nice N-channel MOSFETs.  I like the TI CSD17501Q5A especially, but for use in a switching regulator not as a main power switch.  It's a very fast transistor with low gate charge, low on-state resistance, and fairly low threshold voltage.  However, since speed is not a factor with a user power switch, you want to use simply the lowest on-state resistance with the right gate-source threshold for the battery configuration (single or series cells).  In that case, the best one for a single cell would be the CSD17312Q5;

http://www.ti.com/lit/ds/symlink/csd17312q5.pdf

The best one for series cells would be the CSD16570Q5B

http://www.ti.com/lit/ds/symlink/csd16570q5b.pdf

That IR IRL3803PbF is not a very good pick.  It has a relatively high on resistance at 6 mOhms.  Also it's a 4.5V specified part so it probably does not have an on-state curve far enough to the left for a single cell.  I say probably because International Rectifier does not feel it's necessary to post that curve in the data sheet.  That's critical data and I typically will not use a MOSFET without seeing that "gate-source voltage versus on-state resistance" curve.  It's possible to get an idea from the transfer characteristic curve, but I'd rather see it in black and white.  Notice TI puts that curve boldly on the first page of the data sheet.

Oh, don't want to neglect the P-channels, they can be nicer for mods with other electronics since they switch the high side instead of the low side.  Here's the best P-channel I've seen so far for use as a main power switch in a single cell mod;

http://www.vishay.com/docs/62860/si7157dp.pdf


« Last Edit: August 30, 2014, 08:02:12 PM by CraigHB »

Offline hanukun

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: 49428
  • Posts: 5
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #30 on: September 03, 2014, 12:44:53 AM »
i ended using IRLB8743PBF but once i press the fire button it keeps firing til i take batteries out. and every thing is wired right.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3300
  • Karma: +784/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Unregulated mod and voltage drop question
« Reply #31 on: September 03, 2014, 06:26:40 AM »
i ended using IRLB8743PBF but once i press the fire button it keeps firing til i take batteries out. and every thing is wired right.

N-Channel FET
You will have to use a lower value gate to source resistor that will give you zero volts on drain to batt pos when not fired and full batt voltage when fired. Check under load.
Too low of a resistance will not turn on FET or not turn on fully. Too high of a resistance will not turn off FET or not turn off completely.
« Last Edit: September 03, 2014, 06:30:47 AM by Breaktru »

Offline RoyalWood$

  • Jr. Member
  • **
  • Joined: Sep 2014
  • Location: Middle earth
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #32 on: September 10, 2014, 05:50:44 PM »
I dont have the option to post a new topic. So Im sorry for hi-jacking slightly...

I'm trying to build a unregulated duel 26650. I would like to use a certain button which means I need a mosfet.. Im not sure which one I would use. Does anyone have a link to order the correct one?

Offline RoyalWood$

  • Jr. Member
  • **
  • Joined: Sep 2014
  • Location: Middle earth
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #33 on: September 10, 2014, 05:59:50 PM »
And "Slightly" I mean for posting in an unregulated mod thread  :D

Offline hanukun

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: 49428
  • Posts: 5
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #34 on: September 10, 2014, 06:27:16 PM »
found my issue lol forgot a resistor now it works great

Offline W

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: United States
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #35 on: September 19, 2014, 12:50:11 AM »
I've been lurking around here for quite some time now and finally decided to post.

First of all I would like to thank Breaktru, Manu, CraigHB, David4500 and all the others for sharing your knowledge and helping your fellow vapers in their projects.

I'm almost done with my first mod a DNA30, nothing fancy yet, still waiting for pushbutton in the mail. Now I'm starting to think about the next one and here are my thoughts :
3*18650 in parallel , 1590B , PV5 switch (non rated) so MOSFET , some sort of protection in case something goes wrong, ability to fire very low ohms ~70A

I tried to draw a diagram based on some others I found here, but still don't know what mosfet to use nor what PTC fuse, I just guessed the 15A, any input would be appreciated,

http://imgur.com/qELRlv0

Thanks

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +243/-1
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #36 on: September 19, 2014, 02:44:11 AM »
Welcome to the forum and glad to be of help. 

Just put a pair of two PTC fuses on each cell.  That will get your hold/trip currents where you need them and provide the protection you need. 

Use parallel MOSFETs to get resistance down.  We've mentioned MOSFETs so many times on this forum you should be able to find the links.  You want the lowest on-state resistance (RDS(on)) you can find, but you also need to watch your gate-source threshold to make sure they'll turn on fully with the lower voltage of parallel cells (versus series cells).  Check the chart for "on-state resistance versus gate-source voltage" in the part's data sheet.

Offline david4500

  • Ultra Member
  • ******
  • Joined: Mar 2014
  • Location: Illinois
  • Posts: 227
  • Karma: +50/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #37 on: September 19, 2014, 06:32:34 AM »
ability to fire very low ohms ~70A

ridiculous.

Offline W

  • Jr. Member
  • **
  • Joined: Aug 2014
  • Location: United States
  • Posts: 2
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #38 on: September 19, 2014, 10:52:55 AM »
Not that I'll be doing it but I want my box to have the ability to do it

Offline gsx1000r02

  • Newbie
  • *
  • Joined: Oct 2015
  • Location: USA
  • Posts: 1
  • Karma: +0/-0
Re: Unregulated mod and voltage drop question
« Reply #39 on: October 11, 2015, 04:08:40 PM »
Here's my build. Switch box series/parallel 18650 dual mosfet, voltmeter on the side, will have 2 switches one for master on/off and one for voltmeter always on option. My question is when do i charge the batteries? I'm coming from a regulated mod that just shuts off with low batteries. I think that happens at 3.3v


Offline Daroon

  • Newbie
  • *
  • Joined: Mar 2016
  • Location: USA
  • Posts: 1
  • Karma: +0/-0
  • Gender: Male
Re: Unregulated mod and voltage drop question
« Reply #40 on: March 04, 2016, 04:03:10 AM »
Here's my build. Switch box series/parallel 18650 dual mosfet, voltmeter on the side, will have 2 switches one for master on/off and one for voltmeter always on option. My question is when do i charge the batteries? I'm coming from a regulated mod that just shuts off with low batteries. I think that happens at 3.3v



Interesting, does it show the battery life? These are some pretty big batteries, how long do they last before they need recharging? A lot longer than store bought I would expect just looking at the size of them.

Offline mrzax

  • Jr. Member
  • **
  • Joined: Feb 2016
  • Location: Hungary
  • Posts: 6
  • Karma: +0/-0
Re: Unregulated mod and voltage drop question
« Reply #41 on: March 17, 2016, 06:34:04 AM »
how did you fixed the elements?

Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: Unregulated mod and voltage drop question
 

gfxgfx
gfx gfx
Powered by MySQL Powered by PHP Valid XHTML 1.0! Valid CSS!