Resistance Questions

[EmeraldKiwi]

So here is a setup I'm thinking about getting:
1x Uwell Crown Sub-Ohm tank
1x Sigelei 150w TC mod
4x Samsung 25r 18650 batteries
1x XTAR VC4 charger

And I've got a couple of questions. As far as I know, the mod is run in series, which doubles my voltage to 8.4 theoretically at nominal battery capacity. So, does that double voltage affect how low I can fire my coils?

List of questions:

1. How low can I build with this mod and the batteries above?

2. The Crown tank comes with a .15 Ohm nickel coil head, so will I be able to use it on this mod and with these batteries?

3. If I can't fire the included TC coil, is there a different coil I can purchase to use the temperature control function?

Here are the device's specs:

TECHNICAL PARAMETERS:

Variable Wattage Range: 10.0W - 150W

Joule Range: 10J - 100J

Output Voltage Range: 1.0V - 7.5V

Input Voltage Range: 6.4V - 8.4V

Temperature Adjustment Range: 100-300°C / 212-572°F

Atomizer Ohm Range: 0.1 ohm – 3.0 ohm

Battery: 2* 18650 High-Drain Batteries

Max Current: 35A

Dimensions: 103 x 57 x 25mm ;

product Weight:210g

Total weight：340gg

These came from Sigelei's website.

Another question I have is this:

If the 25r batteries are rated at 20 amps for continuous discharge, how can the mod I chose fire down to .1 ohms?

I'm just mostly confused as to HOW these devices fire so low, rather than CAN they. It says in the specs I can go down to .1 ohms, so I should be able to with 25rs I think. This is where I need a bit of an explanation. Thanks in advance guys!

 

[mauricem00]

without knowing the design of the circuit it would be difficult to answer your question but a step down switch mod power supply only pulls current for a portion of the time so the average battery drain would be less than than the output current if the voltage was lower than the battery voltage. on a 0.1 ohm coil 35 amps would only require 3.5 volts. and produce 122.5 watts the 7.5 maximum output voltage factors in circuit loss so 3.5 volt would only require a 47% on time and a 53% off time or 16.5 amp average drain. a well designed circuit would have an LC input filter to smooth out the battery drain an the 20 rating on the battery is for continuous drain.the peak short term current is much higher on batteries and these units use pulses that are only a few microseconds long with the ratio of on to off time varying with the load resistance. these circuits act just like a transformer. lowering the voltage raises the current for a given input power.

 

[IMFire3605]

In TC mode with that 0.15ohm Crown Coil you will be fine, think the 150TC can fire a TC coil as low as 0.05ohm. I have the standard Sig150watt, I can fire a coil that is as low as 0.1ohm, so I think the firmware in straight wattage mode is about the same. Just remember if you will be running just Samsung 25R batteries in there, your wattage cap should be maximum 100watts, want to go higher then you will need Sony VTC3, Sony VTC4, or LG HB6 30amp batteries. With a VW device it makes up for power by pushing higher voltage, in the series in the 150w and 150TC, you got 8volts to push the wattage up instead of relying on CDR and amps, but don't let that make you think amps don't count, take your max wattage and divide by the volts = your amps

150/8=18.75amps, yes the Samsung can handle 19amps being 20amp CDR, but you still need amps above that to not overstress to stress the batteries to much, thus at above 100watts I suggest 30amp CDR batteries, 11.25 extra amps for those, "WAIT, UHOH, AH CARP!" situations.

 

[dc99]

One thing that seems to get overlooked a lot is the fact that these mods use the batteries in series which means you get twice the voltage but you only get the amperage of one. In other words two 20amp batteries in series is not 40amps.

 

[bwh79]

Don't forget, we're talking about a regulated device here, not a mechanical mod, and so amp drain is a function of the wattage setting and remaining battery voltage only, resistance of the attached atomizer doesn't even play a part. As far as the batteries are concerned, 50 watts is 50 watts, whether you're pushing them through two ohms or two tenths of an ohm.

 

[EmeraldKiwi]

Well, the consensus seems to be that I will be fine as long as I don't go over 100 watts, which seems reasonable. In the unlikely event that I want to fire up to 150 watts, would 25 amp batteries work or would it be better to grab 30 amps instead? I'm not really opposed to either one, but I don't know the pros and cons of each side. Could anyone recommend good 25-30 amp 18650 batteries? Preferably not Sony VTC series because they are counterfeited all day every day. Thanks guys, I really appreciate the help!

 

[Susan~S]

Could anyone recommend good 25-30 amp 18650 batteries? Preferably not Sony VTC series because they are counterfeited all day every day.

This ↓

Just remember if you will be running just Samsung 25R batteries in there, your wattage cap should be maximum 100watts, want to go higher then you will need Sony VTC3, Sony VTC4, or LG HB6 30amp batteries.

 

[IMFire3605]

Well, the consensus seems to be that I will be fine as long as I don't go over 100 watts, which seems reasonable. In the unlikely event that I want to fire up to 150 watts, would 25 amp batteries work or would it be better to grab 30 amps instead? I'm not really opposed to either one, but I don't know the pros and cons of each side. Could anyone recommend good 25-30 amp 18650 batteries? Preferably not Sony VTC series because they are counterfeited all day every day. Thanks guys, I really appreciate the help!

You can get authentic 30amp Sony VTC4 and VTC3 as well as LG HB6 at any of these good vendors online
Illumination Supply
Liion Wholesale
IMRBatteries
RTDVapor
Orbtronics

which are all authorized authentic retailers.

 

[dc99]

I run LG HD2's in mine. They are 25amp but Mooch tested them and said they did fine at 30. I don't use sony's either.

 

[IMFire3605]

In all honesty though I listed Sony VTC3 and VTC4 for 30amp, with how the Sig150 can pull power I strongly suggest the LG HB6, 1500mah yes, but they are true 30amp batteries like the Sony VTC3 and operate well below the temp of the VTC3 as max current below Mooch's tests if battery reaches over 100C in a current test, it fails at that level, the HB6 was at like the 95-100C temp, so could possibly be pushed every once in a while up to the 35amp current the Sig150 is rated for.

*Also refutting what I posted above, the formula on max current the Sig150 can pull, the figure is wrong, not 8.4, but 6.4 the max current voltage figure lowest safe charge state the mod will allow per battery is 3.2v cut off
150watts/6.4volts=23.4375amps it can pull no matter the resistance

 

[EmeraldKiwi]

-snip-

So is a VTC4 not a true 30 amp battery? I'm a bit confused about all this information.

Are you trying to say the VTC batteries get hotter than an LG battery?

What in the world would I need 35 amps for? Like, you said the mod is rated for it, but is that like a max input type of specification?

I understood the other math you did though. At a minimal battery (3.2 volts), 150 watts would require 23.something amps. So at a full battery, (4.2 volts) 150 watts would draw about 18 amps. So it sounds like a 30 amp battery is just what I need regardless because 18 amps is cutting close to the max rating for the Samsung 25r. 23 amps is over the max anyway. But let's say I vape below 100 watts:

100 / 6.4 = 15.625

So even at minimal charge, I could still have plenty of headroom with a 20 amp battery.

For temperature control mode, the mod would fire initially at the full 150 in order to heat the coil quickly right? Is there a way to set the max wattage for "pre heating"? I don't want to fire a mod that goes past what my batteries are rated for.

 

[IMFire3605]

So is a VTC4 not a true 30 amp battery? I'm a bit confused about all this information.

Are you trying to say the VTC batteries get hotter than an LG battery?

What in the world would I need 35 amps for? Like, you said the mod is rated for it, but is that like a max input type of specification?

I understood the other math you did though. At a minimal battery (3.2 volts), 150 watts would require 23.something amps. So at a full battery, (4.2 volts) 150 watts would draw about 18 amps. So it sounds like a 30 amp battery is just what I need regardless because 18 amps is cutting close to the max rating for the Samsung 25r. 23 amps is over the max anyway. But let's say I vape below 100 watts:

100 / 6.4 = 15.625

So even at minimal charge, I could still have plenty of headroom with a 20 amp battery.

For temperature control mode, the mod would fire initially at the full 150 in order to heat the coil quickly right? Is there a way to set the max wattage for "pre heating"? I don't want to fire a mod that goes past what my batteries are rated for.

For Mooch's blog to see the various battery tests you can find it here
https://www.e-cigarette-forum.com/forum/blogs/mooch.256958/

And true the VTC4 unlike the VTC3 and LG HB6 is not a very true 30amp but it can handle 30amp loads, I've used VTC4s in the 25 to 30amp range for well over a year and not a single mishap, vape comparison side by side against a VTC3 or HB6 you can tell the VTC4 reaches 30amps eventually but not as fast and hard as the VTC3 or HB6 does right out of the gate. The VTC5 being higher mah still than the VTC4 is still a 20amp, sacrificed amps for mah, VTC3 1600mah 30amp, VTC4 2100mah 25-30amps, VTC5 2600mah 20amps. But I have a Sig150 regular and IPV3 150watt that I run the LG HB6 in, and with VTC4s I used to run in them, up above 100watts you feel the heat transfer to the mod casing from the batteries getting stressed with continual chain vaping, with the LG HB6s this heat transfer takes longer to notice, in a mech mod with an RDA in the 0.25 to 0.35 ohm range the LG hits right off the bat just as hard as the VTC3 does, true 30amps pulse burst higher than other batteries, so ramp up faster on the coil.

Regarding the TC mode, if you have it set at 100watts/100Joules, the mod from cold standby will dump all 100Joules out of the gate, then once it detects the coil is at set temp it steps down and pulses power to maintain temp or just gradually ramps down adjusting in realtime while power is being applied. Example, Evic VT in temp mode automatically sets itself at 60watts its max output, cold firing is the full 60watts, once the coil reaches say a set 450F it will step down to 15 to 20 watts to maintain that temp, occasionally ramping up to 35 to 45watts when the coil gets to cold, then back down in realtime.

But all in all, yes for a mod that is 100watts plus I tell people Sony VTC3, VTC4, or LG HB6 due to potentially being up at max wattage you'll need the flexing room the 30amps allow, I am one of the many that stress on being as safe as possible, Liion batteries store so much potential power, they give none to very little warning when they get to over stressed, when they go, they go, sometimes dangerously and spectacularly. Just a couple weeks ago we had a News incident reported, younger man on a mech mod with a sub-ohm tank, battery was shorted out on the 510pin of the tank (hybrid direct to battery connector), mod went off like a rocket into the ceiling, young man was wounded badly including puncturing a hole in the roof of his mouth. Would rather questions asked and answered to understand and not just jump right in, just be safe out there, most of the safety and other relevant info is posted on these forums if you just dig right or ask the right question

 

[AzPlumber]

without knowing the design of the circuit it would be difficult to answer your question but a step down switch mod power supply only pulls current for a portion of the time so the average battery drain would be less than than the output current if the voltage was lower than the battery voltage. on a 0.1 ohm coil 35 amps would only require 3.5 volts. and produce 122.5 watts the 7.5 maximum output voltage factors in circuit loss so 3.5 volt would only require a 47% on time and a 53% off time or 16.5 amp average drain. a well designed circuit would have an LC input filter to smooth out the battery drain an the 20 rating on the battery is for continuous drain.the peak short term current is much higher on batteries and these units use pulses that are only a few microseconds long with the ratio of on to off time varying with the load resistance. these circuits act just like a transformer. lowering the voltage raises the current for a given input power.

You can't average the current load on a battery regardless of the on/off time, max current load is max current load.

With out knowing the battery's rate of recovery between pulses any load above the CDR is dangerous.

 

[gofishtx]

You may want to re-think your tank choice. While I have heard a lot of good things about the Crown tank, lately a lot of people have been having problems with the coils not wicking properly. I just got the TFV4 and it is an awesome tank with rba sections available as well as a lot of different stock coil options. The Subtank minis are also decent tanks and I hear good things about the Freemax Starre tanks also. The TFV4 is as good as using a dripper and they also have a mini version coming out that will use the same coils and RBA's. I just ordered the quad and sextuple coils as well as the dual coil rba for mine. If you decide to stick with crown tank, you may want to use a pin to fluff the cotton around the coils before you use them.

 

[bwh79]

So is a VTC4 not a true 30 amp battery? I'm a bit confused about all this information.

What I understand is that it can "safely" be taken up to 30A in that it won't reach the 100°C (212°F) required for a "Fail" grade but that over 20A it may get hot enough (above 75°C or so) to damage the battery and shorten it's lifespan.

 

[EmeraldKiwi]

The VTC5 being higher mah still than the VTC4 is still a 20amp, sacrificed amps for mah, VTC3 1600mah 30amp, VTC4 2100mah 25-30amps, VTC5 2600mah 20amps.

So I suppose in terms of TRUE 30 amp batteries, it's a battle against the VTC3 and the LG HB6. Both of them are 30 amps right? So if one runs cooler than the other, then that's the one I would probably use more often than not. I'll probably just end up getting a few of each of these batteries and see how they perform in my own use scenarios. I've already bought a couple of Samsung 25R batteries, so they should be fine for awhile as long as I don't chain too hard or something to stress them out. But yeah I get where you're coming from. Having a 30 amp battery would let the temperature control shoot up to 150 watts without stressing the batteries, whereas at 20 amps, the batteries may heat up some.

Here's an example for another question:
Say I were to have a 150w device with temperature control. On this device sits a .1 ohm coil. Inside of the device sits two 20 amp batteries.
The chip in the mod is programmed to fire ALL 150w to hit the target temperature, and then back off to maintain that temperature.
I guess it may depend on the chip, but:
Is there any way for me to change a setting somewhere that tells the chip to fire, say, 100w to hit the target temperature instead of all 150w?
I'm guessing the answer is probably not, but let me know otherwise.

I really do appreciate your input man. You are an ECF Veteran for a reason.

You may want to re-think your tank choice.

Nah. I did a LOT of research on good drippers, tanks, mods, etc. and this setup seems to be a good middle ground in terms of user friendliness, performance, and price. The Uwell Crown is very highly regarded, and reviews would have shown the issue you're talking about. I appreciate your thoughts, but I believe that this tank is going to be (recently ordered it, still waiting) a fantastic first pick right out of the gate. Even if it isn't, It's not like I've gone and burnt $500. It was $34. Not a problem to me except I'll be pretty disappointed.


Does anyone know why the VTC4 is labelled on nearly everything I've seen as a 30 amp battery? If what you guys are saying is true, then shouldn't the battery be labelled as a 25 amp or 20 amp or something? I just think it's a bit misleading if it REALLY isn't a 30 amp battery.

 

[AzPlumber]

That's all fine and dandy, but it doesn't matter what the load is as far as I can tell as long as your batteries are rated high enough to handle, say, .5 ohms. If they work for me, and don't get too warm, then I don't really care what the load is. It's when that load becomes an issue that needs to be addressed is when I need to stop and take a look at what's going on under the hood of my mod. And so far, these other forum members are in general agreement that 25Rs are going to be okay for the most part, but a 30 amp battery would be even safer, which is where I'm headed eventually.

You do realize that I was addressing the post that I quoted, right?

 

[EmeraldKiwi]

You do realize that I was addressing the post that I quoted, right?

Oooh. I think I'll just use the magic of editing and delete that and pretend nothing happened. Sound good?

 

[mauricem00]

You can't average the current load on a battery regardless of the on/off time, max current load is max current load.

With out knowing the battery's rate of recovery between pulses any load above the CDR is dangerous.

actually you can with a good input filter of even just a low ESR capacitor across the input terminals.it's done all the time to compensate for feed line inductance.and the spec sheets on batteries show maximum safe current for both continuous and intermittent (peak drain for 5 seconds) loads. I have not found data on the parasitic inductance of these batteries nor have I done test to determine the ramp up time for them but it is common practice to use input filters to average the load on battery powered switch mode devices. I have not seen the schematics for the units used in regulated mods so can't comment on how well they are designed

 

[AzPlumber]

actually you can with a good input filter of even just a low ESR capacitor across the input terminals.it's done all the time to compensate for feed line inductance.and the spec sheets on batteries show maximum safe current for both continuous and intermittent (peak drain for 5 seconds) loads. I have not found data on the parasitic inductance of these batteries nor have I done test to determine the ramp up time for them but it is common practice to use input filters to average the load on battery powered switch mode devices. I have not seen the schematics for the units used in regulated mods so can't comment on how well they are designed

If the manufacturer states a max current draw of 35 amps that's the max current draw. Considering these things are used in front of your face, deviating from the manufacturers specification can be very costly.