True or False: Regulated box mods don't need high discharge batteries when sub ohming

[InfinityzeN]

Oh yea, another little something something.

Higher capacity batteries of the same family are not always better. For example the VTC4 to VTC5. Usable capacity is 2000mAh to 2500mAh. "Great! 25% more battery life for about the same price!" you think. Not so though.

You see, batteries of the same family (chem/cell design) have to make tradeoffs to get higher capacity. The VTC5 might have really great sag (meaning its voltage doesn't drop as much as other batteries at a given amp draw about 1c) but the VTC4 is even better. Up until the VTC4 runs out of juice at about 2000mAh it has higher volts at a given amp draw and total outputed mAh. Since the VTC4 has less sag it doesn't need to put out as many amps to give a total requested wattage. Putting out less amps means the used mAh goes up slower throughout its life.

At very low amp draw (requesting 8~10w total from the battery) the higher capacity battery will last longer (though at a lower ratio than the difference in capacity since the sag is lower in the lower capacity battery) since at that level you are drawing about 1C from the battery. However as you request higher and higher power totals the difference will slowly shrink. If you are a really high wattage vapor then the higher capacity battery will actually hit the point where at the max input amp draw it can not give you enough total watts first.

So if you vape at high watts all day for example, the VTC4 might actually give you more usable life than the VTC5 (that might depends on just how high you vape at). If you are a 5~20w vapor though, the VTC5 will give you more usable life.

 

[edyle]

True or False: Regulated box mods don't need high discharge batteries when sub ohming

Hey y'all,

I was at my local B&M today and was told that now that I have a regulated box mod ( a humble Dovpo E-Mech ), I don't need to worry about buying high drain batteries

Something about the chip takes care of the high drain issue.

If so, it would mean I can buy high capacity batteries and be TOTALLY sure, one pair would last me the whole day.

Something like these Panasonic 3400 Mah bad boys : https://www.fasttech.com/p/1141100

I bought the box to stop having to carry around extra 18650's for my mech mod. My collection includes a k-100 mech with an IGO-W and a Private V2 mech with a plume veil clone. I run both at around .5 ohms

Thanks!

False.

Conservation of ENERGY.

 

[dr g]

watts in watts out ...

 

[stanthemanchan]

The Panasonic 3400 mAh has a 6.8A limit. At 30W your Dovpo is going to be pulling around ~8A, so that battery will NOT be sufficient. If you plan on running at the max wattage you should go with a 10A battery to be safe.

 

[InfinityzeN]

The Panasonic 3400 mAh has a 6.8A limit. At 30W your Dovpo is going to be pulling around ~8A, so that battery will NOT be sufficient. If you plan on running at the max wattage you should go with a 10A battery to be safe.

Even worse than that. The Dovpo is going to pull about 33.4W from the battery to put out 30 watts. It will pull ~8A with a fully charged battery with no volt sag. Since batteries with no volt sag don't exist you are looking at about 8.5A on a full battery. It will quickly go up to 9~9.5A and raise to 10A when you begin hitting a battery voltage of 3.7V.

All the above is using a good battery (VTC, HE2, 25R) with a reasonable voltage sag. That Panasonic will be in pulse and have much worse sag, enough to actually have to pull another amp or two.

As I said before, 1A per 3W of max output you will be using should be your minimum (ie a 10A is the minimum for a 30W output). I tend to try to go above that just to be safe.

 

[IJLimagery]

wow, first of all, thanks to all for your input. I can't say how much I appreciate the wealth of knowledge. what a great learning tool this forum is!

what i've gathered is that there is no magic chip that defeats ohm's law.

InfinityzeN, using your formula:

divide the maximum wattage by number of batteries and then by 3. That is the lowest amp draw batteries I would use in a mod.

The Dovpo has 2 batteries! so... maximum 30 watts / 2 batteries / 3 = 5 amp draw batteries. so the panasonic is 'safe' to use?

Just a note, I have nice batteries. There are 10 in rotation now on my 4 bay Nite core charger. I was buying $13-15 (CAD) green batteries from my local B&M's at first. but given that battery replacement is going to be a constant expense moving forward, the cheapskate in me scoured the internet and fate found me at fasttech. I've started buying pairs of Samsung 25r's for $11 USD. I just order them well in advance of when the ones I have will start to fade.

So, another question or 2 if I may. or perhaps it's better for another thread... but.. is Fasttech a good source for batteries?

I guess this'll be a stupid question and the answer will probably fall under the 'you get what you paid for' category, but I found eFest 35a 2500mah batteries super cheap at ...........com. 5 pieces for $8USD! http://www............com/snapshot/6330818532.html?orderId=64478608175858

They arrived... and well... they work. I guess my question is... is there a useful tool that I can buy that's fairly cheap that I can use to test batteries?

I found this on eBay: NEW AA AAA C D 18650 9V 1 5V Universal Button Cell Battery Volt Tester Checker | eBay

I looked up 18650 explosion on youtube and found this:
https://www.youtube.com/watch?v=ZTzEHsJVZhA
so I'm thinking...... no more batteries from ..........?!

any comments would be appreciated again!

 

[rurwin]

All a cheap battery tester is is a volt meter. It just measures the unloaded voltage. That's enough for you to tell how discharged the battery is.

To really test a battery you need to be able to pull a constant current out of it and track it's voltage from fully charged to "fully" discharged. You won't find that available cheaply.

On the other hand, you can Google for "<battery name> datasheet" and find the discharge curves.

 

[InfinityzeN]

IJLimagery. I would like to point out that the divide by # of batteries is only for parallel (meaning the drain is spread across the batteries). In series (which very few mods are) it is treated as one battery. Most mods are parallel and those that are in series normally tell you so. Parallel means each cell is wired to the pos and neg terminal. Series places the cells in a line (series) and stacks the voltage output. Each has advantages and disadvantages.

Parallel pulls the requested power fairly evenly from all sources (some minor differences, due to slightly different wire lengths and such) which splits the amp requirement evenly and gives you close to the combined capacity of both cells. You want to always use a pair together, treat them as if they were one battery. If one of them ages faster or has issues then it will begin to limit the other cell. Overall though parallel is the lowest stress setup for your batteries as long as you keep them paired. Series stacks the voltage of all cells. However to meet that voltage the capacity is not stacked. It also puts the most stress on your cells.

So two 4.2V 6C 2500mAh cells. Wired in parallel they would effectively be a combined 4.2V 6C 5000mAh cell. Wired in series they would effectively be a combined 8.4V 6C 2500mAh cell.

-----

Fasttech is not really a trusted source of batteries. Batteries are often a clone target and the clones use cheap/nasty cells as often as not. Not something you want to be pulling a high draw from when it is sticking out of your face.

 

[mcclintock]

Regulated mods boost the battery voltage by pulling more current (amps) from the battery. The way they do it, though, the resistance of your atomizer doesn't make any difference as far as battery strain. However, your power settings makes a big difference. For any regulated mod that boosts voltage, you definitely need high drain batteries.

Your dovpo doesn't boost the voltage. Instead, it lowers it from an input anywhere between 6.4 and 8.2 volts (that's why you have 2 batteries). At 30 watts, you're pulling a max of about 5 amps from the batteries, so anything that will do 7 or 8 amps comfortably should be fine. However, you still need to make sure you're using "safer chemistry" or IMR batteries in case something goes wrong. The Panasonics you linked to are 6.8 amp batteries, but they're still the wrong chemistry. If your chip has a problem and the batteries fail, there's still fire involved.

And honestly, you'll probably get better performance out of the usual high drain batteries everyone else uses. If they can do 20 amps, then they're not even breaking a sweat when it comes to 5, which means they'll last a lot longer and you won't have to buy new ones as often. And 2 of them in that mod will last for days between charges.

This is the right answer. Regulators, in this case, are voltage converters and do put out more current than goes in, when the voltage out is lower than going in. And they at least HAVE a protection circuit. Usually....

 

[rurwin]

IJLimagery. I would like to point out that the divide by # of batteries is only for parallel (meaning the drain is spread across the batteries). In series (which very few mods are) it is treated as one battery. Most mods are parallel and those that are in series normally tell you so. Parallel means each cell is wired to the pos and neg terminal. Series places the cells in a line (series) and stacks the voltage output. Each has advantages and disadvantages.

Parallel pulls the requested power fairly evenly from all sources (some minor differences, due to slightly different wire lengths and such) which splits the amp requirement evenly and gives you close to the combined capacity of both cells. You want to always use a pair together, treat them as if they were one battery. If one of them ages faster or has issues then it will begin to limit the other cell. Overall though parallel is the lowest stress setup for your batteries as long as you keep them paired. Series stacks the voltage of all cells. However to meet that voltage the capacity is not stacked. It also puts the most stress on your cells.

So two 4.2V 6C 2500mAh cells. Wired in parallel they would effectively be a combined 4.2V 6C 5000mAh cell. Wired in series they would effectively be a combined 8.4V 6C 2500mAh cell.

In a regulated mod, it doesn't matter whether the batteries are in series or parallel, the formula works in both cases.

In series, the battery voltage is higher so the drawn current is smaller for a given output voltage. In parallel half the current is drawn from each battery so the requirements for each battery are smaller. Maths being the beautiful thing it is, everything cancels out and the formula works.

That is not the case for a mechanical mod, of course.

 

[IJLimagery]

Ok... so on the FT discussion page... there is a guy that said he asked Dovpo and they confirmed that the batteries are in SERIES. that's good, right?

from Infinite's comment: Series stacks the voltage of all cells. However to meet that voltage the capacity is not stacked. It also puts the most stress on your cells.

so, I'm getting 7.4 Volts.... but the capacity is not stacked? that would explain why I'm not experiencing a lot better battery life now that I have a 2 18650mAh device. serious bummer. :T

Looks like I bought the wrong device. If my goal is a device that will allow for longer battery life so I don't have to carry around multiple batteries, I should look for a dual 18650 device that is run in parrallel, and buy high drain batteries. is this right? I was looking at the IPV 3 but found that it doesn't have a pass through ability. (I leave a mini usb charger at my desk at work so I can pass through during the day)

from Rurwin's comment: "In series, the battery voltage is higher so the drawn current is smaller for a given output voltage. In parallel half the current is drawn from each battery so the requirements for each battery are smaller. Maths being the beautiful thing it is, everything cancels out and the formula works"
may I ask... what formula are you referring to? V = I x R ?

so, in series V = 7.4 at minimum... I'm running a 0.5 ohm dual coil build... so, if ... V / R = I I am drawing... 14.8 Amps?
that doesn't sound right.. hmm.... that would mean by running in series... you'd increase current. why would anyone wanna do that? does more current increase power therefore 'quality of vape'?

from this site: Electrical Formulas

P = Vsquared / R so... wired in series, devices, such as the Dovpo, are designed to increase power capability at the expense of current draw? but then... why is the Dovpo's maximum wattage limited at 30 watts? (7.4 x 7.4) / 0.5 = 109.52 watts

is this where the 'step down' occurs? if so, what purpose does it serve?

I'm so confused.

 

[rurwin]

from Rurwin's comment: "In series, the battery voltage is higher so the drawn current is smaller for a given output voltage. In parallel half the current is drawn from each battery so the requirements for each battery are smaller. Maths being the beautiful thing it is, everything cancels out and the formula works"
may I ask... what formula are you referring to? V = I x R ?

This one:

The way I quick calculate it is to figure lowest point will be 3v after efficiency and sag. So divide the maximum wattage by number of batteries and then by 3. That is the lowest amp draw batteries I would use in a mod.

If the mod is regulated, it does not matter whether the batteries are in series or parallel, the battery life will be the same. It will be twice the life of the same mod with a single battery when run at the same power.

With a mechanical mod, putting a battery in series increases the power output by a factor of four. Both batteries are providing twice the current, so the battery life will be halved. On the other hand, if the batteries are in parallel then the power at the coil remains the same as for a single battery and each battery only supplies half of the current, so the battery life is doubled.

With a regulated mod the voltage and current are transformed by the electronics. The thing that remains the same is the power. So V x I at the battery equals V x I at the atomiser. (Ignoring about 15% inefficiency.) If the battery voltage doubles, then the battery current must halve in order for that equality to remain true.

 

[Angel Eyes]

the answer to the original question is technically TRUE for those with step down and the right chip, but FALSE in most situations.

You want a high amp battery if you vape like a lot of folks, but for some folks, it is possible to take a step down capable chip such as DNA 40 and subohm (carefully) with a lower amp battery, here is an example using the DNA 40:

you could build a 0.14 ohm coil (which is very sub-ohm), set your mod to 7.14 watts and that would result in 1V and 7.14 amps - 7.14 amps is not really a high discharge, kinda medium these days. But most folks vape at higher wattage with this low of a resistance, so most folks should get high discharge batteries to be safe!

Looks like I bought the wrong device. If my goal is a device that will allow for longer battery life so I don't have to carry around multiple batteries, I should look for a dual 18650 device that is run in parrallel, and buy high drain batteries. is this right? I was looking at the IPV 3 but found that it doesn't have a pass through ability. (I leave a mini usb charger at my desk at work so I can pass through during the day)

by the way, for the folks who are interested in very long battery life, that is what step down and low current vaping will get you, so if you like long battery life, I'd get a DNA 40 based device!

 

[Angel Eyes]

I'm so confused.

I think this site will make your Ohm's law math calculations easier ---> watts - volts - amps - ohms calculator

remember to hit the reset button after each calculation to zero the fields!

 

[InfinityzeN]

Angel Eyes
That is the output. However the draw off the battery will be much lower in amps. Say the two batteries in his mod are at 3.8V current charge. After sag (which will be really low for outputting 7.14 watts) and efficency you are looking at maybe 2 amps total draw. Only about 1 per battery. If the batteries are almost completely discharged (say 3.2V) you are looking about about 2.5 amps total draw or 1.25 amps from each battery.

With the mod he is using using two batteries and having a 30 watts limit, you are looking at a max of about 5 amps per battery draw when the batteries are almost completely discharged and the mod is firing at 30 watts.


IJLimagery
The formula for calculating output voltage is: Square Root of (Requested Wattage * Ohm). If you set a mod to 8 watts and have a 2 ohm coil, the mod will adjust it to 4V output.

The formula to find amp draw from a battery is: (Requested Wattage / (battery voltage - sag)) / Mod Efficency. If your batteries are at 4.1V charge and we are guessing about 0.05V sag (so low because we will be pulling 1C from the batteries) then (8 / (4.1 - 0.05)) / 0.9 = just under 2 amps. That is not quite 1 amps per battery

Wattage increases total heat divided by the size of the coil. More power to the same coil makes the vape warmer. If you double the total area of the coil and double the power, there will be no change in the max potential temp of the two coils. However the larger coil will have roughly twice as much surface area to transfer that heat energy to ejuice and make vapor. As long as you have the wicking and airflow to support it that is. Wicking and airflow are just as important as power for the quality of the vape.

There is no difference in effect between 8V at 2A, 4V at 4A, and 2V at 8A. They all will produce 16 watts of converted heat energy in the coil.

 

[InfinityzeN]

Aright, real world example time. Guys don't beat me up to much since I am breaking this down barney style.

So we will look at power using the example of cargo trucks delivering goods to a location 5 miles away.

Volts = Max Speed of Truck in round trips per hour (10mph per volt)
Amps = Cargo Capacity of Truck
Watts = Total goods delivered per hour

So if you have trucks going at 40mph (4.0V) and with 4 tons of cargo (4.0A) they will deliver 16 tons (16W) per hour to a place 5 miles away if it had no load/unload times and worked nonstop.

Now to add in Sag and Efficency.

Sag = Lower speed due to weight of cargo
Efficency = Load/Unload Times for another delivery route

When your trucks carry lots of cargo (Amps), they end up having to reduce their speed (Sag) because they can't travel as fast. The more cargo (Amps), the more speed they lose (Sag). If your trucks are rated for heavy cargo (battery rated for higher amps) then they don't loose as much speed (less sag) when they have heavy loads (lots of amps).

Off loading the trucks and putting their cargo into trucks in a different size running at a different speed (changing the Output Voltage) reduces the total goods (Watts) you can deliver. How much by is based on the quality of your crew transfering the cargo (Efficency).


Very simplified but it should give you the basic idea.

 

[catalinaflyer]

Not going to get into giving my opinion about true or false on the mod not needing high drain batteries. I use batteries rated well beyond the highest drain I may ever put on them regardless of whether it's a regulated mod or mechanical. If there were some magical chip that could supply more power to a coil while taking less energy from a battery then using that fuzzy logic we should be able to build a mod that produces Kilowatts of power using thin air for batteries.

What caught my attention is the OP's talk of 10 batteries in rotation for one 2 battery mod and a constant need for replacing with new batteries. I started vaping 18 months ago and still to this day am using the first two Efest 1600 V1 batteries I purchased with my first mod. They have been in such devices as a VTR, 134, SID, all manner of mechanicals, an IPV3 and Sigelei 100W Plus. No they are not married, I have no friggen idea which one is which or which position they may have been in (I'm not into voyeurism) but I charge them in my original Nitecore charger, slap them in my Sigelei or IPV in whichever slot they land in and vape an entire day while still showing 50% remaining at the end of the day.

In fact I just looked, I have 2 Efest 2000 V2 button tops both purchased at different times, a pair of EH 2000 button tops that I have no idea where I wound up with those, some green (I think Samsung but its so old I can't read it) button top, a purple battery, again unknown, a blue battery also unknown and finally I have 3 Sony batteries I did actually buy all at the same time in the same place for my SMY 260 only because I did not own 3 like batteries. I dropped them in, hooked up the USB charging cable and they lasted a week before I charged them again which was a week and a half ago.

Now with all that being said, the "unknown" batteries were used in my 134 and VTR which had no chance of needing more amperage than they could deliver. I know when I bought each one of them I was aware of the capacity and adhered to that. I still use an SID and 134 occasionally and keep those batteries just for that purpose. As for the others, I use my Nitecore to charge the ones for the Sigelei and IPV and don't give a rats rear end which slot they go in. All the hoopla about rotating batteries falls on my deaf ears, my laptops have been using 18650 batteries for years and not one single time have I had to take them out and rotate them. Nor do I have to take them out to charge them so I don't feel like there's a need to take the batteries out of my SMY 260 when the onboard charger does just fine, they're in series.

So now that I'm off my soapbox, what exactly are you doing to your batteries that requires them to be replaced with new ones so much??

 

[catalinaflyer]

Series or Parallel,
The short and nasty way to tell is which way the batteries are oriented in the mod. If the positive's of both (or all three) batteries are in the same direction, good chance it's a parallel circuit. If the poles of the batteries are opposite each other (1 battery with positive towards the top of the mod and the second battery with the positive towards the bottom) really good chance they are series.

All the mods I own using more than 1 battery are series not parallel. It's much easier for a chip to get up to very high wattage with series current being fed to it (higher voltage) than it is for it to have to take lower voltage and step it up to get higher wattage.

 

[AttyPops]

What caught my attention was his regulated (buck) mod uses two batteries IN SERIES.

The main thing to note here:
1) The max amp rating of the two series batteries is the max amp rating of ONE of them. You don't double the amp rating when you put batteries in series. You do double the voltage, thus probably needing less amps to begin with.
2) Any device has loss...not all current makes it to the coil. This is even true for mechs. However for regulated mods, particularly those with a booster...you need to pay attention to the INPUT current (just as others above have said) since it will draw "extra" amps to boost the voltage. And you probably don't know how many even if you have all of the ohm's law formula memorized. It's a circuit efficiency thing, and may vary by device. So they generally REQUIRE high-amp batteries.

Of course the buck mod only reduces voltage, so you're close using ohms law...derate the amp usage margin by maybe 10% (total guess). So assume it uses 10% more amps than you think it will by ohm's law on the coil voltage and ohms. Again, total guess. I'd still use IMR in it.

3) Saving $$$ or adding MAH ratings by using batteries that are not high-amp can be short sighted. You probably want high-amp batteries anyway just in case you get another device that requires them. Also, the IMR class batteries are safer.

Now, all that said....I use Li-Ion protected batteries in series in my buck mod because that's what we used to use "in the old days" and I'm still sitting on a stash of batteries. I DON'T DO sub-ohm with it though. And my next ones will be IMR. My box mod has 3 layers of protection (cut-off, and two batteries each with an over-amp protection circuit) and also cannot build up pressure. So I continue to use them. But that's me.

 

[dr g]

Unprotected li-ions in series are a no-no.