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Battery safety in mech mods for beginners

allen

Postman
Joined
Dec 30, 2012
Messages
915
I apologise in advance if anyone thinks this is teaching them to suck eggs. This is primarily aimed at people who are thinking to try a mech mod but don’t really have a grasp of how to know if their planned set up is considered ‘safe’


In the time I’ve been on POTV I’ve seen a recurring theme of questions come up and it generally reads along the lines of
“I’m thinking about getting a mech mod. The batteries I’ve got are (insert name and model) – are these okay to run a coil of 0.XX ohms?”
I don’t really like answering the questions as there’s a risk I get the gnarled (and burned) finger of blame pointed at me if their batteries go
upload_2017-2-23_17-52-35.png


The flipside of this is the possibility that they will do some crazy shit if no one answers the question and an avoidable kapow happens. So, all I want to do here is present some basic info people can access, weigh up the risks and make their own decisions.

First point:
As a rule of thumb, the higher your battery capacity is, the lower it’s Amp rating will be.
At the time of writing and according to Mooch (a well respected guy who tests batteries to help us all be safe) the highest reliable capacity battery out there is 3,500mAh with a 10A rating, IF the battery in your hand seems to good to be true - it probably is.

Second point:
You, me, anyone…. Can buy replacement battery wraps with anything we want printed on them. It could be your favourite superhero. But it also could be “5,000mAh capacity, 40A”.
Just because something is written on a battery, my dears, doesn’t make it true!
So, if you’re thinking of buying a battery from a well known auction website that claims to have a capacity of 10,000mAh (they’re on there, I checked) then please think twice. There’s a very very good chance that it’s not real.


I mentioned Mooch earlier. You’ll find his blog here
Mooch's battery data blog
And within that blog you’ll find the link: 18650 Battery Ratings - Picking a Safe Battery To Vape With

In there you will find not only the manufacturers ratings of their batteries but also ratings he has worked out through stringent tests. Please DO read his disclaimers though. He states:
“Caution: You are responsible for your own safety! The conclusions and recommendations I make here are only my personal opinion. Carefully research any battery you are considering using before purchasing. This table is only meant as a first step for you to use in narrowing down the best choices for the way you vape. Do not use it as the only source of information when picking a battery to use! This is especially true if you intend to use a battery at over its continuous current rating. I am not responsible for any damage or injury sustained by anyone using this table to select a battery.”

Or to put it another way, if you choose to buy and use a battery, you’re responsible for your own actions.

Once you’ve selected a battery, where do you buy it. I will simply say – from a reputable source. If you want recommendations, ask the other Apes, they’ll gladly let you know where they buy theirs.

When you’ve got that battery in your hands, always, always, always give it a check over before you put it in a mod!

1)The wrap needs to be completely intact. In many mech mods (especially tube mods) the whole of the mod is part of the circuit. On your battery, everything covered by the wrap is the negative connector. This means that if any part of the wrap is split the battery can come in contact with the mod casing and will complete the circuit…… AND YOU WON’T BE ABLE TO STOP IT. This is a bad situation to be in as your battery will overheat, vent and very likely explode. so please folks, check those battery wraps before putting them into a mod.

2) there will be a small insulator disc around the positive connecter, under the wrap – you will be able to see it. It is usually black or white. Check that regularly too. Same applies.

So, when you’ve selected and bought a battery, how far can you safely ‘push it’?
Well, for a starter, you need to understand ohms law. This is the relationship between volts, resistance, wattage and amps.
In all likelihood, you’ll know resistance and voltage. 18650s charge up to 4.2V and both amps and wattage are highest when the battery is full – so ALWAYS work using 4.2V for safety’s sake.

Amps = volts / resistance e.g 4.2V / 0.5Ω = 8.4A
Watts = volts² / resistance e.g. 4.2V² / 0.5Ω = 35.3W

You might also be wondering, what’s lowest I can go with my battery rated at XXAmps?
Well, the lowest you can SAFELY go is:
resistance = volts / Amps e.g. 4.2V / 20A = 0.21Ω

So, if your battery is rated at 20A the lowest recommended resistance is 0.21Ω. Yes, some people will say you can possibly go lower safely, and may well go lower themselves. I’m not going to tell you any such thing……. It’s your battery, mod, hand and face – if you want to weigh up the risks and go lower, feel free but don’t blame anyone except yourself if things go awry. ;)
I, personally, take that risk but I will never ever advise anyone else to do the same as me.


If maths isn’t your strong point, there are other ways to get the numbers.
One easy way is this easy online calculator ohmslawcalculator.com
All you need is to pick 2 values you know and it will work the rest out for you
You can use volts with resistance or amps or watts and it will work out the rest for you. Easy peasy.

I’ve also prepared this (dreary looking) table that simply gives you watts and amps, in a grid, from the resistance and voltage. Frankly, be safe and only use the left hand column as that is the 4.2V column.

ohms.png

The last link I’ll share is this: steam-engine.org battery drain page
It can give you an indication of how long you can expect a battery to last you depending on the resistance of your coil. There are some other great resources on that website such as the coil wrapping page to help you work out what material / coil size will get you the resistance you want to aim for.

Anyway, that’s all I can bothered to type
I hope it helps someone work out for themselves what they can safely do with the equipment they’ve got.

Vape on!
:vapinape:


EDIT: I deliberately left out dual cell unregulated mods as these are not an area inexperienced vapers should venture into. Ever.
But, as they exist I at least want to explain the BIG difference between parallel and series unregulated devices
because ..... here be monsters!
1.jpg



Basically, if they're in series, 2 batteries definitely does NOT equal safer as they double the voltage and, therefore, double the amps; The maximum watts, however, will be quadrupled!
using the same example as above:

Amps = volts / resistance e.g 8.4V / 0.5Ω = 16.8A
Watts = volts² / resistance e.g. 8.4V² / 0.5Ω = 141.12W

In Parallel, something very different happens. the amp load gets spread between the two batteries.
BUT as there is 'something' (bits of wire or lumps of metal) joining positive to positive and negative to negative, this 'something' already adds some resistance into the equation. The recommended way to allow a safety element for the completely unknown resistance of the 'something' is to only rely on HALF the amperage of the second battery. So, using 2 x 20A batteries DOESN'T mean you can safely vape at 40W...... it means 30A would be considered safe.

Bottom line, if you're going to go crazy and buy a dual cell unregulated mod please, please, PLEASE make sure you know if they're in series or parallel and double check what this means for you.

In summary

1) if you're inexperienced or remotely unsure what you're doing - don't get a multiple cell unregulated mod. End of.
2) parallel cells mean your resistance can go a bit lower
3) series cells mean you need to DOUBLE the resistance you used to use. (this'll give you the same amps but more watts)

PS, if anyone spots mistakes in this post, please let me know so I can correct it
 

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Vape Superstore
no need for beginers to use mechs by todays mods standards 5 years ago all that learning was not a option it was a journey i thought when the vamo came out nothing would beat it lol
 
Vape Green
no need for beginers to use mechs by todays mods standards 5 years ago all that learning was not a option it was a journey i thought when the vamo came out nothing would beat it lol
For me the order was
Ego
Spinner / twister
Mech
Z-max (button kept breaking)
Mech..... Only reliable mods available at the time.

Aaaah the good old days. Lmao
 
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The Electronic Cigarette Company
AcmeFog
Going to use my first mech today and by my reckoning a 0.28 coil with fully charged 4.2 18650 comes out at 15A and my 18650 can handle 20A. So should be good for 183 draws. Great informative thread thanks for the info

ImageUploadedByPlanet of the Vapes Forum1491734520.021276.jpg
ImageUploadedByPlanet of the Vapes Forum1491734530.783351.jpg
 
Premier Ecigs
@Michael jackson , that is around where I build for my mechs, 0.25-0.3, using dual coil, 26G SS316L.

I find this to be a nice area for me, and battery life is surprisingly good. What mech have you gone for? I own quite a few, but my favourite by far is a Wotofo Phantom. It just seems to work the best out of all my mechs, and I use it with the standard top cap, not the Hybrid style connection.

@allen , a fantastic guide here for using mech mods :). As long as people follow your guide and stay sensible, there should be no accidents or people losing hands due to not understanding what they are doing.
 
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