CDR or pulse

[Zutankhamun]

I always ask questions here. Much more direct answers. Was sifting through some 18650 guidelines & I always work with continuous as opposed to pulse. Even though its safer, I am not sure why. Can the battery be pressed and discharged until it is flat when using the CDR. How long can you discharge the battery by pulsing when you havn't exceeded the pulse rating. Is it just a matter of seconds? This question is confusing. Hope you can work out what I mean. Cheers

 

[EBates]

There is no true measure of what the Pulse Rating is. You could be good assuming 1 sec or it could be 5 sec. But in either case you could be over the CDR limit and cause a problem. I do not intentionally run any of my batteries above 75% of their CDR. Just me.

 

[Zutankhamun]

K thanx. I mostly use 25rs and run regulated mods with high builds. No problem. I fancy trying my mech clones with VTC4s and running them at .3 maybe .2 Just want to be well within the limits. I think the .3 is like 15A discharge but somebody just said the VTC4 is 20 but was safely tested to 30A. That is more than safe I take it.

 

[suprtrkr]

Pulse ratings are usually measured in microseconds. They're useless for vapers. Stick with the CDR and you'll be fine. The 25Rs will be great in a regulated mod with high builds. I wouldn't take a mech mod (single battery) below about .4 unless you are sure you have authentic VTC4s.

 

[JMarca]

I could say a battery is good for a 40 amp pulse rating and if I just hit the fire button and let go immediately after 0.5s I would theoretically be correct (which is sort of useless). Pulse isn't really a standard nor should it be taken too seriously, CDR is what matters, at least to those who vape at low ohms/high wattage, I've never come close to the danger zone on a 20 amp battery so I go for better MaH ratings.

 

[Baditude]

This topic is controversial with "some" vapers. Those who vape "extreme sports" style with super sub ohm builds will say they use the pulse rating of the battery safely. I beg to differ...

Unlike the "continuous" rating, pulse ratings are for the most part unreliable. They are not an industry standard, and every manufacturer seems to have their own idea of what a pulse rating is. It could be milliseconds or a few seconds. Not being an industry standard, it makes comparing specs between different brands impossible. The continuous rating (CDR) is an industry standard, so you can compare specs between models and brands.

Plus, you have an ever-growing number of battery manufacturers who are advertising inflated ratings to push sales above their competition. Independent testing often reveals performance is half of what is promised.
List of Battery Tests
There are no 18650 batteries with a genuine rating over 30A!

If you build your coils to the pulse rating, you are IMHO instantly "over-specced". Should you develop a hard short, you won't have time to discover the problem and work out a fix before a battery vents. If you use the continuous rating, you have a margin of safety built in. You'll notice a problem, and have time to remove the atomizer or battery immediately, and avoid a potential catastrophy.

Take for instance, you unknowingly have a loose post screw on your RDA. I always build 0.6 ohms, and one day I took a vape and it was unusually harsh. I did a ohm check, and the resistance was 0.1 ohm. I checked that the post screws were snug, and one was loose. I retightened it, and again it was 0.6 ohm. Now what if my build had been 0.2 ohm? Dropping 0.5 ohms would have caused a hard short (0.0 ohm) and vented my battery! At 0.6 ohm I had a margin of safety.

Mooch and myself have written some blogs that you might find useful:

Battery pulse ratings are useless!
18650 Safety Grades -- Picking a Safe Battery to Vape With
A Beginner's Guide to Your First Mechanical Mod
Explain it to the Dumb Noob: Ohm's Law Calculations
Battery Basics for Mods

 

[AzPlumber]

Food for thought:
High amp pulses on a new battery can not be compared to high amp pulses on a battery damaged by high amp pulses.

 

[Baditude]

Food for thought:
High amp pulses on a new battery can not be compared to high amp pulses on a battery damaged by high amp pulses.

This is true:

1.0 ohm = 4.2 amp draw
0.9 ohm = 4.6 amp draw
0.8 ohm = 5.2 amp draw
0.7 ohms = 6 amp draw
0.6 ohms = 7 amp draw
0.5 ohms = 8.4 amp draw
0.4 ohms = 10.5 amp draw
0.3 ohms = 14.0 amp draw
0.2 ohms = 21.0 amp draw
0.1 ohms = 42.0 amp draw
0.0 ohms = dead short = battery goes into thermal runaway

Everyone is free to set their own parameters, and I can only say what mine are.

I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 20A batteries, that would be 10A. The above Ohm's Law Calculator tells me that a .4 ohm build is as low as I would want to use.

The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the batteries c rating (amp limit). So down the road, your 20A battery may only be a 10A battery.

If you build to a pulse rating, your battery is going to age much faster than if you use the continuous rating.

 

[93gc40]

K thanx. I mostly use 25rs and run regulated mods with high builds. No problem. I fancy trying my mech clones with VTC4s and running them at .3 maybe .2 Just want to be well within the limits. I think the .3 is like 15A discharge but somebody just said the VTC4 is 20 but was safely tested to 30A. That is more than safe I take it.

.3ohm is 14amps at 4.2volts, it more amps with more volts and less with less, .2ohm is 21 amps at 4.2. for this reason 3ohms is the lowest I go on a single 18650 battery. Mechanical or wired.

 

[Zutankhamun]

Well I never need that low a build anyway. .4 does it for me, possibly .3 It just seems crazy when I saw a guy use 80 watts & a 0.08 build on a tc mod. Just had a look and its 31 Amps, not insanely high amperage but surely that's a dangerous game to be playing no matter what batteries.

 

[Baditude]

It just seems crazy when I saw a guy use 80 watts & a 0.08 build on a tc mod. Just had a look and its 31 Amps, not insanely high amperage but surely that's a dangerous game to be playing no matter what batteries.

I'm not an expert with TC mods, but I'm told that they can actually use lower ohm builds than other mods. Regulated mods also use a different Ohm's Law formula for figuring amp draw than a mech mod.

Calculating battery current draw for a regulated mod

Plus, a regulated mod has protection circuitry which can keep you out of harm's way, while a mechanical mod does not. With a mechanical mod, you're on your own.

 

[93gc40]

Well I never need that low a build anyway. .4 does it for me, possibly .3 It just seems crazy when I saw a guy use 80 watts & a 0.08 build on a tc mod. Just had a look and its 31 Amps, not insanely high amperage but surely that's a dangerous game to be playing no matter what batteries.

He most likely also had 2 or more batteries to fire at 80watts. Also you gotta consider amps applied to the atomizer vs drawn from the battery when dealing with a regulated mod. One of the nice thing about regulated mods is they can give you some wiggle room on battery safety rules along with being able to provide more or LESS power than the battery can by itself. In a regulated mod, when bad things happen, the circuitry tends to fail before the battery does. Most of the time, that failure protects the battery from damage. But, 30amps is about all I would ask of 2 18650 batts, regulated or not. Most of the time, isn't the same as all of the time.

 

[MorpheusPA]

Baditude and I use a similar standard--the CDR as tested by a completely reliable independent source (such as Mooch), or the rated CDR, whichever is lower.

Then I divide by 2. So my LG HG2 batteries are rated for 20A, I won't draw past 10A.

(In practice, I'm so far under the CDR it's laughable and I could use batteries with a lower CDR and higher mAh rating. I don't because I prefer the excess safety factor above and beyond my specifications).

That gives you plenty of margin for an aging battery, or one that got slightly damaged and you didn't realize it. It also extends the battery life since it's never under severe stress.

At the battery's CDR, it should be perfectly safe to discharge it from full to empty in one constant stroke. However, that will cause heating, and heat equals aging in the case of a battery. Batteries used that way will tend to be toward the bottom of the normal curve for aging--don't expect more than 250 cycles.

The pulse rating, if the specifications are known, could be used...but I consider it too great a risk. Many manufacturers don't publish the spec, and it can be anything from milliseconds to seconds. Again, this also ages the battery before its time.

 

[Thrasher]

These batteries where not designed for sustained output at max level.

The pulse is tricky because......

The manufacturer sets this value, and you have to find a data sheet that shows what they set as a pulse time in their tests, there is no standard.

And, the high draw pulse is an internal safety margin, used to protect the battery from high amperage spikes, say from a fan motor starting, or like hard drilling with cordless tools.

In other words the pulse is there as a shock buffer to protect the battery from being destroyed. Not how much potential energy the battery contains for use.

Always remember there is no such thing as a vapers battery, when you remove what we are doing with them and realize no other users in different industries would ever consider designing a product that draws more then the cdr can safely handle you realize all these beliefs are simply unsafe.

 

[WattWick]

Well I never need that low a build anyway. .4 does it for me, possibly .3 It just seems crazy when I saw a guy use 80 watts & a 0.08 build on a tc mod. Just had a look and its 31 Amps, not insanely high amperage but surely that's a dangerous game to be playing no matter what batteries.

The resistance of the coil is not a factor in calculating amp draw from a battery - when powered via a regulated mod. In a regulated (with or without TC) mod, the battery does not directly power the coil. It powers the mod - which in turn powers the coil.

If you ran a 0.08 ohm coil on a (theoretical) mechanical mod - and disregarded all efficiency loss and voltage drop - 4.2 (theoretical) volts would give you a (theoretical) current of 52.5 amp and a (theoretical) output effect of 220.5 watt.

A TC mod, on the other hand, does not care about the resistance of the coil for any other purpose than constantly measuring variations in resistance. As the coil heats up, coil resistance increases. This increase in resistance allows the mod to calculate the temperature of the coil. So, while a mechanical mod outputs whatever a coil allows for - a TC mod outputs up to the set wattage to a coil that starts at a certain resistance. Once the coil has reached a (calculated target) increase in resistance, the wattage drops from the set wattage to whatever it takes to maintain that target resistance.

 

[MorpheusPA]

a TC mod outputs up to the set wattage to a coil that starts at a certain resistance. Once the coil has reached a (calculated target) increase in resistance, the wattage drops from the set wattage to whatever it takes to maintain that target resistance.

It always seems like people are a little hazy on what that means, though, as the implications aren't exactly as easy as W=I^2*R.

(for the OP as I know WattWick already knows this)
Basically, one's set wattage shouldn't exceed the cutoff battery voltage times the CDR.

Most of our mods seem to cut off around 3.2, but there are exceptions. For the purpose of the argument, I'm using 3.2. If you don't know, 3.0 is generally a reasonably safe number.

If your CDR is 20, 3.2 x 20 = 64 watts, the maximum output that would be safe on your battery.

Again, I only use half the CDR, so I call the maximum 32 watts with a 20A battery, and then round down to 30 watts.