concerns about subohming

[WattWick]

Once you realise that all the limitations are down to using batteries, the glamour of ultra-low ohms goes away.

Buy Embedded Switch Mode Power Supplies (SMPS) 240W 1 Output Embedded Switch Mode Power Supply (SMPS), 15V, 20A Excelsys XG3 online from RS for next day delivery.
That's 15V at 20A, or 300W, fully isolated from the mains with current limiting in case of shorts. At 15V, a 100W coil is 2.25 ohms, so it's pretty safe to build accurately.

I'm not saying it's a good idea. Personally I haven't wanted more than 20W. And I'm not saying that using that beast is safe; you'd have to know what you were doing to build with it, but it's a hell of a lot safer than pushing Lithium batteries to their limit and trusting a cheap resistance meter below 0.2 ohms.

Couldn't agree more. If my memory serves me, you were into RC planes? I fly helis myself, and have always wondered what's the big deal with high wattage vaping as a source of peer appreciation. Heck, my biggest heli can easily pull 1500 watts. All from batteries. And that's just a medium sized (500) heli. I guess that makes me 10x as cool as those who vape at 150 watts

 

[Susan~S]

I.E., I am running a .7 ohm coil, so if my math doesn't fail me, with a fully charged battery @ 4.2V, I'm hitting around 6A / 25W of power...

My batteries are rated at 35A max discharge rate... 35A > 6A

Correct me if I am wrong people

You are correct -- 4.2v @ 0.7ohm = 6A

Just an FYI on those 35A max discharge rate batteries. If your batteries are the purple Efest 18650 2500mAh 35A batteries -- they are not 35A continuous. They are really rebranded LG18650HE2 2500mAh 20 amp continuous batteries.
Source: Baditudes Blog: Battery Basics for Mods: IMR or Protected ICR?

Here is another warning that was posted on ECF regarding another purple Efest battery: Efest 3100mAh battery caution

 

[jsiddlehfx]

You are correct -- 4.2v @ 0.7ohm = 6A

Just an FYI on those 35A max discharge rate batteries. If your batteries are the purple Efest 18650 2500mAh 35A batteries -- they are not 35A continuous. They are really rebranded LG18650HE2 2500mAh 20 amp continuous batteries.
Source: Baditudes Blog: Battery Basics for Mods: IMR or Protected ICR?

Here is another warning that was posted on ECF regarding another purple Efest battery: Efest 3100mAh battery caution

Good to know, still pulling less than a third of its max discharge, but I appreciate the info! Pretty sure the B&M I got em from would like to disagree lol

 

[Baditude]

Good to know, still pulling less than a third of its max discharge, but I appreciate the info! Pretty sure the B&M I got em from would like to disagree lol

Continuous discharge rate is a battery industry standard and applies to all battery manufacturers. Pulse discharge rate is a very grey area as there is no agreed upon standard and is left up to each manufacturer/vendor to decide what they define it as. Not a very reliable spec to compare one battery to another. I personally do not pay any attention to pulse ratings and consider them to be redundant and meaningless. Pulse ratings give a false sense of security. My .

 

[jsiddlehfx]

battery says "Current Discharge: 35A" Now I know its really 20A, but is that continuous discharge or pulse?

 

[Baditude]

battery says "Current Discharge: 35A" Now I know its really 20A, but is that continuous discharge or pulse?

20 amps continuous discharge. Pulse is 35 amps. IMHO, Efest is "bending the rules" by advertising the pulse rating instead of the continuous. As you can see, this confuses consumers into thinking the battery is better than it actually is. A false sense of security which doesn't really exist.

There's a big difference between 20 amps continuous and 35 amps continuous if you are using a 0.2 ohm or lower coil.

 

[jsiddlehfx]

20 amps continuous discharge. Pulse is 35 amps. IMHO, Efest is "bending the rules" by advertising the pulse rating instead of the continuous. As you can see, this confuses consumers into thinking the battery is better than it actually is.

Makes sense, they rebranded a battery and placed the pulse rating on the wrapper instead of continuous rating, am I correct?

And the reason we know the continuous is by looking up what batter is under that wrapper? Is there a way to really test what the continuous rating is?

 

[Baditude]

Makes sense, they rebranded a battery and placed the pulse rating on the wrapper instead of continuous rating, am I correct?

And the reason we know the continuous is by looking up what batter is under that wrapper? Is there a way to really test what the continuous rating is?

Manufacturers determine the continuous discharge rate from the C rating of the battery.

Efest re-wraps the LG18650HE2 battery and adverises it as a "35 amp battery" right on the wrapper. LG says it is a 20 amp continuous discharge rated battery, with 35 amps being the pulse rating. Consumers often don't know the difference between continuous and pulse, so they will have a false sense of security using the "superior" 35 amp battery, when it is only a 20 amp battery. The way I see it, Efest is being deceiving and disreputable to unknowing and uneducated consumers. Look at how many vendors & owners of that battery believe it is a 35 amp battery.

Removing the wrapper to see what cell is there is one way to identify the battery's real specs. Independent testers also have sophisticated equipment to plot a batteries true specifications.

Efest has a history over-rating and misrepresenting their battery specifications. Company representatives have lied to consumers by saying "All Efest batteries are made by the parent company", when it has been proven that Efest rewraps batteries made by Sony, LG, and Panasonic. You can draw your own conclusions to this information.



The purple Efest 2100mah 30 amp battery is a re-wrapped Sony 2100mah 30 amp VTC4 battery.

 

[tj99959]

Makes sense, they rebranded a battery and placed the pulse rating on the wrapper instead of continuous rating, am I correct?

And the reason we know the continuous is by looking up what batter is under that wrapper? Is there a way to really test what the continuous rating is?

Formula: (C-Rating) X (AH) = Maximum Constant Amp Draw

Now to use this formula you first need to convert your battery size from the common MilliAmpHours to AmpHours. A MilliAmp is One-Thousandth of an Amp. So here are some Examples of converting MilliAmpHours to AmpHours:

800mAH = .800AH
1350mAH = 1.350AH
2200mAH = 2.200AH

Just understand that many battery manufacturers exaggerate the mAh of their batteries to create an illusion of a higher Amp rating. That's WHY many of us suggest not exceeding 50% of the continues Amp rating.

 

[jsiddlehfx]

Formula: (C-Rating) X (AH) = Maximum Constant Amp Draw

Now to use this formula you first need to convert your battery size from the common MilliAmpHours to AmpHours. A MilliAmp is One-Thousandth of an Amp. So here are some Examples of converting MilliAmpHours to AmpHours:

800mAH = .800AH
1350mAH = 1.350AH
2200mAH = 2.200AH

Makes sense, whats C rating?

 

[Maurice Pudlo]

I was there for that VapeBlast Mod Explosion... It was pretty intense... Sounded like a bomb, shrapnel went through the roof...

The way I look at it, if you have a functioning, clean mod, with vent holes and you stay a good amount within the max discharge rate of the battery(on noted good quality batteries), you will be ok...

Always check your batteries for physical defects by looking them over and checking its charge after charging it.

I.E., I am running a .7 ohm coil, so if my math doesn't fail me, with a fully charged battery @ 4.2V, I'm hitting around 6A / 25W of power...

My batteries are rated at 35A max discharge rate... 35A > 6A

Correct me if I am wrong people

Shrapnel went through the ceiling tiles.
You do not have a 35A discharge battery.

Good to know, still pulling less than a third of its max discharge, but I appreciate the info! Pretty sure the B&M I got em from would like to disagree lol

You may want to consider finding a new B&M.

battery says "Current Discharge: 35A" Now I know its really 20A, but is that continuous discharge or pulse?

20A continuous at best, without seeing it who knows. Your shopping at a sketchy place so you might just have some very unsafe battery out of a laptop, again, who knows.

I run 0.5 ohms measured on a meter that has an error of +/-0.15 ohm, so my coil might be 0.65 ohms or 0.35 ohms, with that in mind I use Sony VTC4 30A continuous discharge batteries. At most I'm pulling 12A at 4.2V, less than half of the battery's maximum continuous discharge rate. I consider that reasonably safe in terms of battery stress.

Your 0.7 ohm coil could be as low as 0.55 ohm considering the +/-0.15 ohm error on our little ohm meters, so at 4.2V your drawing 7.64A.

Is that safe for your battery, I don't know, if its a dumpster battery in a purple shrink wrap it might not be, again who knows.

Maurice

 

[tj99959]

Makes sense, whats C rating?

Charles-Augustin de Coulomb's C-Rate for Batteries

 

[jsiddlehfx]

Charles-Augustin de Coulomb's C-Rate for Batteries

Read that page, but still a little fuzzy as to how I figure out the C rating of a battery

 

[tayone415]

Good to know, still pulling less than a third of its max discharge, but I appreciate the info! Pretty sure the B&M I got em from would like to disagree lol

Some employees just don't know, I went in to one B&M and the guy kept telling me that the 35 amp Efest was better than a VTC5 and why would I think the Efests sells out way faster than the Sonys?

I told him, because people don't know what they're buying and that it is a 20 amp continuous discharge and the performance of the vape doesn't hit as hard with the Efest.

He still thought Efest better in the end.

20 amps continuous discharge. Pulse is 35 amps. IMHO, Efest is "bending the rules" by advertising the pulse rating instead of the continuous. As you can see, this confuses consumers into thinking the battery is better than it actually is. A false sense of security which doesn't really exist.

There's a big difference between 20 amps continuous and 35 amps continuous if you are using a 0.2 ohm or lower coil.

^^^This^^^

Just to add to this, watch out for other batteries, not just Efest. I picked up the "40 amp" Vamped battery by Vapor Cells, I was told it was a 40 amp battery by a shop, and said he was sure it was continuous. I went to a different shop that had it and the guy said it was 20 amps continuous. After going online and searching, I came across a ton of online stores saying it was "40 amps" but found a couple saying it was 20 amps.

 

[Ryedan]

Read that page, but still a little fuzzy as to how I figure out the C rating of a battery

Battery manufacturers test batteries to find the amp hours of capacity they hold and express that as milliamp hours (mAh), or for bigger batteries like car batteries, amp hours (Ah). A 1 Ah battery, or 1000 mAh, will discharge at 1 amp for one hour and then be completely empty. A 1A draw is considered a 1 C rate of discharge for that battery. At 10 C, the battery will be putting out 10(C)*1A=10A but it will only be able to do that for 60 (minutes)/10(C) = 6 minutes.

A 2600 mAh battery like the VTC5 will by definition do 2.6A for one hour. Sony has, I think, rated the battery at 30A continuous. Too figure out the maximum C rating for that battery, 30A/2.6Ah=11.54 C.

The VTC4 at 2100 mAh = 14.29C max.

Keep a couple of things in mind though. When battery manufacturers rate a battery for mAh, they do so at extremely low amp rates and they take the batteries down to the lowest voltage the battery will tolerate. No one uses a battery for vaping at 0.2A draw and down to 2.5V.

The maximum continuous amp draw rating is IMO not an exact number and should be used as a starting point only if someone plans to get close to it in use.

 

[skoony]

its interesting to note that these ratings are dependent upon the internal heat of the battery remaining at or below a certain
temperature.
i think in the future heat venting strategies will become important.

what i would like to know is what is the recommended discharge rate of a battery?
i have seen factory spec indicating max continuous current draw but,i have not seen
any thing on a manufacturers site recommending one to do so.
regards
mike