# Design too close to battery limit?



## Viper_SA (11/9/21)

Wasn't sure where to put this, as it's not really about batteries alone, so I hope this will be okay.
Yesterday I noticed something for the first time while playing with my new vaping app on my phone. I own three Drag X mods, and the best flavor I get on the by far are from the VM6 0.15 Ohm coils. I used to run these at 35W, but recently upped it to 50W. The recommended wattage for these coils are 60-80W.... Now I run these mods on Samsung 25R's, which has an Amp rating of 20A. I noticed the following on 50W on the calculator




Just over 18 amps! WTF?! That is higher than the recommended 10% gap to leave on the battery rating.

Then I calculated what it would be at recommended wattage




Is there something I'm missing here because these are regulated mods? Seems very irresponsible and unsafe to me to sell these pods kits to noobs who would never check this. Thank goodness after I mucked about with the firmware the coils don't adjust to the recommended wattage every time it is removed and put back on. I immediately dialed down to 40W from 50W to get closer to 17 amps to leave the 10% safety margin. 

Anyone have any thoughts on this?

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## Silver (11/9/21)

You are right @Viper_SA 

problem is that the mod doesn’t know which battery you have inserted
Imagine you have a 15 amp CDR battery and you fire it with the above config at 80W
A short pulse or two “probably” will be ok
But the problem is if it gets stuck in a firing position in your pocket then things could turn out not so good

ohms law is ohms law, regulated or unregulated

maybe @Kuhlkatz can just have a look as well - his knowledge in this area is tops

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## DarthBranMuffin (11/9/21)

The mech legends can chime in too here... @vicTor 
@Stranger 

And our resident "engineer"
@Intuthu Kagesi 

Quite an interesting question there @Viper_SA . As for my builds and use I am always in the safe zone, but yes, what if a noob gets something like an AWT battery that you have no idea what it's actual rating is. That will hit the news again and put vaping back 10 years.

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## Grand Guru (11/9/21)

This would probably be right if you were using a mech mod without any bells nor whistles but I think the fact that these are regulated mods makes all the difference… it’s all about the fancy little components that step up the power on those batteries without actually pushing them to the limit…. my 2 cents.

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## Grand Guru (11/9/21)

Besides, 25Rs aren’t the best batteries I’d use on a regulated mod. I’d rather go for the Samsung 30Qs, the LGs or the Molicells

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## Viper_SA (11/9/21)

Grand Guru said:


> Besides, 25Rs aren’t the best batteries I’d use on a regulated mod. I’d rather go for the Samsung 30Qs, the LGs or the Molicells



If the Molocell group buy happened earlier I would have gotten them, but is it stands I replaced all my old batteries a month or two before that. I do indeed use 30Q's for my low wattage mtl setups but I've always preferred the 25R for higher wattages. It's what I used all through my mech journey without incident so I just trust them. Plus I like the green

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## Intuthu Kagesi (11/9/21)

What @Silver stated unfortunately is true ... manufacturers don't know what battery(ies) you're going to be using, and pass the the responsibility on the owner / user of the mod in question. 

As such ... I only use Molicels, AND I have put 20Amp "resettable fuses", (PTC's), in all my mods as an additional precaution, furthermore, I do discharge tests every so often and calculate the internal resistance so that my cells remain closely matched and paired.

This was after I noted something shocking, (_no pun intended_), in that the PWM, circuitry in most, (_all_?), mods runs *A LOT* higher than the average voltage displayed on your mod screen ... *What is displayed is an EFFECTIVE voltage* ... in actually you have pulse of current hitting your coils a LOT higher than what your mod says it is, albeit for a short period, (said period adjustable in duty cycle as an EFFECTIVE voltage)

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## Silver (11/9/21)

Thanks @Intuthu Kagesi !

by the way, for those who may not know, the old (now discontinued) Reo mech mod has a “hot spring”
The original mod master Rob from Reosmods made it so that if there is too much current going on or a short , the spring “melts” and sags downward under the battery, opening the circuit 

the spring doesn’t actually melt, it’s just made out of a material that deforms when there’s too much current / heat. I don’t know what it’s made of but that’s how it functions. In my 7 yrs I only recall this happening once. And it was when I was trying to do some volt checking on the posts and I think I accidentally created a short by touching the two posts with the same probe. Then it took me about half an hour to figure out why the mod wasn’t working. Very clever

In those days you could buy additional springs, they were cheap. And then just swap it out if yours “melted”

Rob from Reosmods didn’t trust that the user would always know what they were doing. So he made use of this simple thing.

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## Intuthu Kagesi (12/9/21)

Silver said:


> Thanks @Intuthu Kagesi !
> 
> by the way, for those who may not know, the old (now discontinued) Reo mech mod has a “hot spring”
> The original mod master Rob from Reosmods made it so that if there is too much current going on or a short , the spring “melts” and sags downward under the battery, opening the circuit
> ...



We need more emoticons, I didn't know which one to select, and went for a reply ;

You're welcome, with respect my response, and ... Thanks for the info on the Reo ... I wish ALL manufacturers would add in protection circuitry, however chances of them doing it are minimal for anything other than mods with factory fitted cells, (_an' we jus' love 'em don't we jus' _).

The good news is that mods generally have more than enough space in them to fit a couple of 20Amp, (_or lower?_), PTC devices, (I use the Marcom MS-PSHT available from Mouser, Mantech, and other Electronic Component companies), however even one of the manually re-settable fuses typically used to replace vehicle fuses could be used in series with Mod battery leads .... they're really inexpensive in the greater scheme of things, and I highly recommend their use!

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## Raindance (12/9/21)

Regulated mods modify the voltage and current received from the battery and what is fed to the atomiser is not related to what is drawn from the cells. To test this place an ammeter in the battery circuit and fire the mod. The “in” current is normally limited to around 19 Amps.

A 200W mod will also not deliver that output over the full range of its reported atomiser resistances. In fact, these outputs can only be achieved over a very small portion of this spectrum. 

the long and the short of it, without going into detail, is that as long as your cells can safely handle 20 or more Watts, are in good nick and well cared for, you need not worry.

For added peace of mind, verify the max input current which should be listed in your mod’s specifications.

Regards

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## Intuthu Kagesi (12/9/21)

Raindance said:


> Regulated mods modify the voltage and current received from the battery and what is fed to the atomiser is not related to what is drawn from the cells. To test this place an ammeter in the battery circuit and fire the mod. The “in” current is normally limited to around 19 Amps.
> 
> A 200W mod will also not deliver that output over the full range of its reported atomiser resistances. In fact, these outputs can only be achieved over a very small portion of this spectrum.
> 
> ...



I'm going to agree to disagree with you on this one I'm afraid ... 
Whilst I have yet to experience an 18650 meltdown in one of my mods, I have had a pair vent on me rather violently, so I'm choosing to err on the safe side. Mass manufacture has errors built into it, and ... I would prefer not to become a statistic on what I consider a potential bomb ... namely the humble UNPROTECTED 18650 that we use, to which my opinion / comments would be;

"_To test this place an ammeter in the battery circuit and fire the mod. The “in” current is normally limited to around 19 Amps_".
To measure the peak values accurately you would require an oscilloscope, as this is a squarewave of varying duty cycle, to which most multimeters limitations on maximum frequency and their "True RMS" feature would cloud the actuality, (_refer to my post above_).

"_as long as your cells can safely handle 20 or more Watts_" 
You surely mean Amps?

"_For added peace of mind, verify the max input current which should be listed in your mod’s specifications_"
Input current? Are you referring to current draw from the batteries or current supplied to a load? ... the latter is generally specified as a maximum wattage, to which current would have to be calculated, and the former is usually not specified?

I do however agree that you should ensure that your cells are in good nick, _(I don't just mean visually_), and that you should read all the manuals ... I would add to that, that at minimum, you should familiarise yourself with Ohms Law and purchase a decent Ohm Meter should you be using "rebuildables" 
When all is said and done ... err on the side of caution ... whilst we're all free to choose, we don't need to become Darwin Award recipients.

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## Raindance (12/9/21)

Intuthu Kagesi said:


> I'm going to agree to disagree with you on this one I'm afraid ...
> Whilst I have yet to experience an 18650 meltdown in one of my mods, I have had a pair vent on me rather violently, so I'm choosing to err on the safe side. Mass manufacture has errors built into it, and ... I would prefer not to become a statistic on what I consider a potential bomb ... namely the humble UNPROTECTED 18650 that we use, to which my opinion / comments would be;
> 
> "_To test this place an ammeter in the battery circuit and fire the mod. The “in” current is normally limited to around 19 Amps_".
> ...


In response:
Batteries are DC so a normal ammeter should do.
Yeah, I did mean amps,
True, few manufacturers actually publish max draw and even fewer the resistance range their mods will deliver claimed max output on.

Example used here is for the Therion 166, note the 166 uses the 250 board limited down so the max draw of 28 Amp does not apply. Applies only to a three cell mod capable of 12.6 Volts.




Also note the actual range of resistance the full output can be achieved.



We thrashed all of this out in a thread here somewhere a few years ago. Think it was under battery safety.

Regards

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## Silver (12/9/21)

Thanks guys for the great feedback

Last few yrs I vape at around 20-30 Watts, seldom more than 25 Watts. 
(am now back to being exclusively MTL)

My coils never go below 0.5 ohms
So my amps at even 30 Watts and 0.5 ohms is I=sqrt(P/R)=sqrt(60)=7.7 amps
The batteries I buy all have a minimum of 15 amps continuous discharge rating (CDR)
So I think I am ok in any sort of mod

However, I am mostly at about 20 Watts and about 0.8 ohms - so that would imply a paltry 5 amps.

I like what @Intuthu Kagesi says about monitoring overall battery health though.
I am in need of replacing my batteries - I have been using the same ones for quite a while
But I have plenty, so the amount of cycles theve been through each is probably under 100

Would be great if @Intuthu Kagesi could recomment a decent quality ohm meter?
And where one can get it?

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## Intuthu Kagesi (12/9/21)

Raindance said:


> In response:
> Batteries are DC so a normal ammeter should do.
> Yeah, I did mean amps,
> True, few manufacturers actually publish max draw and even fewer the resistance range their mods will deliver claimed max output on.
> ...


My issue with using a multimeter for current measurement is that even the best, my Fluke for example can only measure current *reasonably accurately* to 10Amps continuous, and 20Amps maximum, (actually 19.99 Amps), for 10 seconds as I recall?, however that isn't the issue ... It's that the current being measured *isn't DC* ... it's a pulse width modulated square wave, and as far as I know, they have yet to invent a multimeter capable of measuring a variable duty cycle square wave to provide an "effective voltage", (or current in this case), result ... enter the Oscilloscope ... now should you use an Oscilloscope, and measure the voltage across your atty, and then using an accurate meter, measure your atty resistance, you can calculate the peak and effective current flow.

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## Kuhlkatz (12/9/21)

Contrary to what is mentioned, higher capacity cells typically only support lower current draws. The 3000mAH cells are typically rated at 15 or 20A, and 2500mAH typically support higher current draws of 20-25A. Please note that these are CDR ratings, i.e. fully on all the time Constant Discharge Rating at 20/25A, not a 3-5 second burst like when you vape. Cells can support higher 'burst' discharges at higher rating than their CDR ratings.
Still, best is to look at Mooch'es battery ratings. 
Also be aware that for Samsung 25R and 30Q cells, there are way too many fakes out there.

@Viper_SA , as @Raindance mentioned, the COIL end is physically separated from the BATTERY end of the circuit, so you typically have to do seperate calculations for each 'side' of the equation.
Ohm's law still do apply, but the voltage that is applied to the coil is not directly derived from the battery which can only supply a fixed voltage. This obviously drops as the battery discharge with use. We can use the fully charged voltage of the battery at 4.2v, the nominal voltage of 3.7v and the lowest voltage that we expect the mod to cut off, which is 3.3v for some, or 3.2v as the lowest accepted for the 'calcualtions'.


On the COIL side of things, we know 2 values - the coil's resistance and the supposed dialed in 'power' in watts.
Using the Ohm's law (including Joule's Law) wheel, we can calculate the voltage across the coil to deliver 50 Watts of power using a resistance of 0.15 ohms.



So we end up at the 18.26A you mentioned.

However... For the actual current draw from the battery, we cannot use the 2.74V as we know for a fact that the battery is at a higher voltage than that.

For the battery side of things, we know (or we think we know) the battery voltage should be somewhere between 4.2v and the cut-off of 3.2v. We do know that we dialed in 50W as a power setting, and no matter how inaccurate the resistance reading of the particular mod is, the power is always calculated based on it's reading of the coil resistance and what voltage needs to be applied to the coil to reach 50W for that resistance.
No matter how cheap or expensive the rest of the electronics, this calculation should always be the same, unless they used pre-schoolers to develop the firmware.

In a perfect world, based on the 50W, and a full cell voltage of 4.2V we can thus deduce the actual current draw from the battery.
Power = Amps X Volts, so Amps should then be Power / Volts...
So for a full cell voltage, the nominal cell voltage and the lowest cell voltage, we get the following current draws:



As you can see, we start off at 11.90A, which increases as the cell voltage drops to 15.63A.
This is assuming that there is no power loss and a 100% efficiency in the electronics, which is never the case.

Recalc that at a 90% efficiency, and we end up with:



So, 13.1A going up to 17.19A for 50W, which is still 'OK'-ish, even for most 3000mAH cells.

Crank that up to 80W, and you are over what most batteries are rated at:



Starting off at 20.95A and ending up at 27.5A when the cell is flat. 

This is territory where you should be using a dual battery mod for your own safety:

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## Intuthu Kagesi (12/9/21)

Silver said:


> Thanks guys for the great feedback
> 
> Last few yrs I vape at around 20-30 Watts, seldom more than 25 Watts.
> (am now back to being exclusively MTL)
> ...



Here's a fairly decent and inexpensive suggestion ... I use this for vape related odds and ends ...
It has a claimed accuracy of 0.8% of reading, plus 5 digits on the least significant bit, however it's calibration certificate shows 0.1% + 1 digit accuracy, (luck of the draw ) ... the attatched PDF has the specifications and distributor details in it, else ... JH Christensen is where I purchase most of my measurement and other tools and equipment from.
Out of interest sake ... note the reading on the 2" long test leads prior zeroing.

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## Silver (12/9/21)

Thanks very much @Intuthu Kagesi 
Will check it out

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## Stranger (13/9/21)

Just seen this thread and I can't add anything to the extensive explanations above, other than the fact that we now know that regulated mods will use DC-DC to get to the desired wattage and have in built protection for over voltage and under voltage.

I have a mate whose portable vacuum cleaner packed up, so he decided to rebuild the battery pack, off he went to the china shop and bought some COOLFIRE 18650 batteries.

Apparently the meltdown was quite spectacular.

Reactions: Like 1 | Funny 7


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## DarthBranMuffin (13/9/21)

Stranger said:


> COOLFIRE 18650 batteries



I am guessing it wasn't a very cool fire...

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## MIKE6236 (13/9/21)

So if I understand correctly. On @Kuhlkatz 's post, I'm safe vaping 0.24ohm at 65watts on a dual battery mod? Or am I just ignorant and still know nothing after trying to read and understand that post.
I know that my mod performs differently on all wattage intervals as it should, but after hitting 100watts and higher, it hits the same all the way. 
100watts to 160watts has absolutely no difference.

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## Feliks Karp (13/9/21)

MIKE6236 said:


> So if I understand correctly. On @Kuhlkatz 's post, I'm safe vaping 0.24ohm at 65watts on a dual battery mod? Or am I just ignorant and still know nothing after trying to read and understand that post.
> I know that my mod performs differently on all wattage intervals as it should, but after hitting 100watts and higher, it hits the same all the way.
> 100watts to 160watts has absolutely no difference.



If it's *regulated* and a reputable brand you are safe, I do 0.15 ohm at 65w on a single battery mod, the needed voltage to get the selected wattage comes from the chip, however constant bucking/boosting will wear out the chip at some point. Will that wear cause a battery vent? Maybe, but the mod will most likely start malfunctioning in other ways before then. I have only ever dead-shorted a battery in a regulated mod (insulator ring had come out), there's not a real way to protect from that beyond good battery practice.

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## Puff the Magic Dragon (13/9/21)

For those of you who are new to vaping don't panic when you see the type of discussions in this thread.

The safest thing to do is to only buy batteries that have been recommended by Battery Mooch and only buy from reputable vendors. Mooch advises what batteries are best for what type of mod. 

Take a look at his YouTube channel here :

https://www.youtube.com/channel/UCePHh3NMvu3rW2LFJeOWo-Q/videos

You can read all of his reviews and see his charts here :

https://www.e-cigarette-forum.com/blogs/mooch.256958/

If you want to know anything about battery safety just start a thread.

There is only a handful of good (not safe) batteries. Some are "better" than others when used in mechs vs regulated mods, and others are better suited for low resistance (high amp) coils.

If in doubt, just ask a question on the forum....don't take a chance.

Good batteries are really cheap when you take into account how long they last. It is not worth trying to save on buying cheap, unknown batteries. You will spend way more on juice in a year than you do on batteries.

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## MIKE6236 (13/9/21)

Feliks Karp said:


> If it's *regulated* and a reputable brand you are safe, I do 0.15 ohm at 65w on a single battery mod, the needed voltage to get the selected wattage comes from the chip, however constant bucking/boosting will wear out the chip at some point. Will that wear cause a battery vent? Maybe, but the mod will most likely start malfunctioning in other ways before then. I have only ever dead-shorted a battery in a regulated mod (insulator ring had come out), there's not a real way to protect from that beyond good battery practice.



Thank you very much. My battery's are double wrapped and I try my best to keep it in good shape. I have re-wrapped a couple of my friends battery's that was mostly about 3 months old. Their conditions were horrible. After Re-wrapping I sent them a video of a battery venting. Hope it will open their eyes.

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## Puff the Magic Dragon (13/9/21)



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## Silver (13/9/21)

Kuhlkatz said:


> Contrary to what is mentioned, higher capacity cells typically only support lower current draws. The 3000mAH cells are typically rated at 15 or 20A, and 2500mAH typically support higher current draws of 20-25A. Please note that these are CDR ratings, i.e. fully on all the time Constant Discharge Rating at 20/25A, not a 3-5 second burst like when you vape. Cells can support higher 'burst' discharges at higher rating than their CDR ratings.
> Still, best is to look at Mooch'es battery ratings.
> Also be aware that for Samsung 25R and 30Q cells, there are way too many fakes out there.
> 
> ...



Thanks for the comprehensive response @Kuhlkatz !!

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## Kuhlkatz (13/9/21)

MIKE6236 said:


> So if I understand correctly. On @Kuhlkatz 's post, I'm safe vaping 0.24ohm at 65watts on a dual battery mod? Or am I just ignorant and still know nothing after trying to read and understand that post.
> I know that my mod performs differently on all wattage intervals as it should, but after hitting 100watts and higher, it hits the same all the way.
> 100watts to 160watts has absolutely no difference.



Hi @MIKE6236 , as some of the other guys already mentioned you should be safe if you use a good set of batteries from a reputable vendor.
There is no harm in doing your own research or asking others if unsure what batteries is best, but most would recommend a visit Mooch's resources on his blog at ECF : https://www.e-cigarette-forum.com/blog-entry/moochs-recommended-batteries.7593/

With mechanical mods, the coil resistance of the build is the most critical factor as that directly affects the current that will flow through the circuit.
Common sense is the only thing that prevents people from blowing themselves up. This relates to using Ohms law, a good multimeter and a decent battery or set of batteries with the knowledge to use a coil resistance that would not push the battery limits beyond their design or specs. 
Unfortunately, a lot of people replace the 'common sense' part with a 'pair of steel cohones' when they build, especially for cloud chasing.

When using a regulated mod, the coil resistance is far less of a factor and probably should be the least of your concern. The power that you dial in to deliver to the coil, coupled with what your battery / batteries can deliver is the most important bits. That said, keep in mind that certain mods only supports coil resistances in a specific range, so if the coil is outside that range, the mod typically will not fire at all, or may not deliver the correct or the 'maximum' power.

Without going into any fancy details, one thing to note is this part at the bottom of Mooch's recommended battery list that most people miss, ignore or probably just never read:



So for a single battery mod using a Samsung 25R, rated as 20A max CDR, you should be OK at up to 60W. With a fresh battery at 4.2v the current draw would be around 15.71 Amps. When calculated at 3.2V or the safe cutoff for Li-Ion batteries, the current draw will be around 20.63A, slightly above what the 25R is rated as.

If you have a dual battery mod, the work is divided amongst the batteries, no matter whether they are in serial or in parallel. So for the same 25Rs, you should be safe up to around 120W.

For a set Samsung 30Qs rated at 15A (20A when not exceeding 75 degrees C), that would be 45W in a single battery mod and 90W for a dual battery mod.

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## Stranger (14/9/21)

@Kuhlkatz 

Thanks for the above, I don't care how many times this is repeated on this forum

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