AAE-C Battery Power Guide - Discussion Thread

[Ripshod]

Jun 6, 2015 9:34:23 GMT hijack said:

I can see this is going to be debated much more.
Is it the case then, that the voltage drop seen in a battery under load is a reaction to the stress of said load and the drop in voltage does not diminish the stress that is placed upon it and only serves to maintain same level of stress?

EDIT: SRY so slow putting my thoughts to paper my Question may have already been answered. I need to have a read first

In fact the stress is reduced as the battery won't have to deliver the whole 20Amps. This affects everything with the battery, including internal heat. Simply, every stress is reduced.

Jun 6, 2015 9:37:57 GMT markm said:

By deducting the voltage drop, you are effectively saying that the battery didn't have to do that work.

Bang on. As soon as a battery is asked to do the work expected it falls short. Of course you could work the calculations in reverse to ensure you DO get that 20Amps, but with that being on the limit I wouldn't recommend it.

[markm]

I think this is about where the voltage drop is occurring, internal to the battery
Is different from external in the mod.
My experience of mechs tells me by far the largest drop is caused by dirty switches.

[hijack]

At what point does the battery 'give up' then ?

[Ripshod]

I know peeps have been sub0uming for years now, and over that time the batteries have improved so much things like the IR and Volt drop have become a concern.

However there's an emergence of newer cells with much higher IR.

AWT have a 20/35Amp battery with an IR better than 0.08 Ohms. So better could mean 0.079 Ohms. Draw 20Amps from that and we get a calculated 3.05 Volts at the battery's terminals.

I'm not denying the resistance of the whole mod will reduce this drop, but at what point will a cell become useless (and dangerous).

The AWT I've been testing will only deliver 52.2 Amps through a dead short - maybe that's what the makers believe will make them safer batteries.

[hijack]

EDIT: I think i can see what your saying Ripshod. The voltage will drop, and HEAT will be the effect. The battery will 'give out' when the heat becomes to much for it to bear? and that will occur if you continue if you continue placing too much stress on it?
But the drop in voltage does reduce the impact but if you go to far overheating will be the result?

[Ripshod]

That's the other point hijack, one I don't mention too much, but it's probably more relevant to us as vapers.

20Amps through a 0.08 Ohm battery will produce anything up to 32 Watts under perfect conditions. That's a lot of internal heat. There's so many variables though, as already mentioned the mod and coil come into play here and affect the maths, I'd expect 24 Watts to be nearer the mark. Still a lot of heat though.

[hijack]

Yeh i see the point. Its is dependent on the resistance of Mod, its switches, the batteries internal resistance as to what one would consider a safe working load.

[muckyboy]

Sorry to thread jack a little but I have some Sanyo UR18650FM cells.

Are these any good? Safe, dangerous or lethal?

[VapingBad]

Jun 6, 2015 10:55:05 GMT muckyboy said:

Sorry to thread jack a little but I have some Sanyo UR18650FM cells.

Are these any good? Safe, dangerous or lethal?

I would not use it vaping myself, a lowish powered, 15 W or less regulated device is the only vaping gear you should ever use it in, defiantly not mech or higher powered mod.  Its max current is only 2 C, so continuous is probably below 4 A, and it is not safe chemistry so do not let it get hot.

[hijack]

Jun 6, 2015 10:55:05 GMT muckyboy said:

Sorry to thread jack a little but I have some Sanyo UR18650FM cells.

Are these any good? Safe, dangerous or lethal?

These are the type of battery that I would try replace at some point with a safer chemistry battery, but VapingBad is right in saying in can be used in lower power electronic devices as these devices have built in protection, unlike that battery which should really be sold with its own protection circuit.
Just be cautious with it, and if you see any damage to the wrapping, 'bin' it.

[Ripshod]

It IS a protected ICR. The board trips at 7.6Amps, 52% over the max current (the 2C rating means 5Amps).

UR18650F (same spec as UR18650FM according to Sanyo)

Further info

Still, I'm agreed, not recommended for vaping.

[hijack]

The data sheet describes the protection that is required in the battery pack for safe operation...The single cells are unprotected.

The ones i saw had a red wrapper maybe they do both

Yes i think intl-outdoor have re-wrapped the Sanyo so it has the circuit, as the original are a cell for use in a pack  

I think all ICR that you can get in unprotected form are designed to be use in a pack with with the protection in the pack rather than the individual cells.

Thats why I didnt like the idea of 'pack' ICR's being broken up and used as cheap batteries for vaping, as even the manufacturers tell you they need protection.

[Ripshod]

At least 80% of the Sanyos that I've seen for sale are protected, and most of them are vaping vendors. So I made the assumption.

muckyboy do you have a link we could look at.

It's so refreshing to see the term 'SAFER' used rather than 'SAFE'.  thumb up As 'SAFE' implies nothing can go wrong.

[Ripshod]

I've had a think about this markm, and of course you're right about the dirty switch. The problem is what do we actually include when working this out. We're trying to keep it simple for everyone, but the mods we use and the batteries themselves make this impossible.

The internal resistance of the cell has only become a topic of concern because of the heat issue and the fact that the IR of cells is generally on the rise - making even more heat.

In the calculation for a coil should we consider the resistance of the mod itself? We could easily change the info I'm giving to include the mod, so we could say for a 20Amp cell the overall resistance should be 0.21 Ohms. Then if a mod is measured (when freshly cleaned) at 0.1 Ohms should we say it's safe to build a coil at 0.11 Ohms? What would happen then if the wrap was not seen to be damaged and the cell shorted to the tube, bypassing the switch. If the switch was 0.05 Ohms that would leave 0.16 Ohms constantly across the 20Amp cell until the cell is removed (mathematically 26.25Amps).

Of course in this situation the IR of the cell would save the day.

I'm not including the resistance of the mod in my calculations for the coil. In the same vein I'm not including the IR of the cell.

The only reason the cell's IR is being considered at all is the heat that is generated because of this IR. Anything I consider too high will eliminate the cell from my list.

More 'hardcore' subohmers are aware of all this and will measure everything and do the calculation for every build.
The beginners' maths is a straight R=V²/W = 17.64/20 = ~0.88Ohms for a calculated 20Watt vape.
In real life the only way to get 20Watts from a 0.88 Ohm coil with a single cell is with a regulated mod. A mech will fall well short, in a safe way.


If you want to help you already have, for sure. But if you want to help further I'd appreciate it. If we can condense EVERYTHING down so we can include it in a single post, in a way newbie subohmers can understand it'll make it all the more safe.

Of course we could do a partII and partIII later to expand peoples' knowledge, unless we put them in danger of cerebral meltdown! <<< Not a derogatory comment.

[markm]

I was just worried that people might read your comment and interpret it as safe
to do their AMP calculation based on the measured drop voltage, when its considerably safer
to use the fully charged battery voltage.
The relatively small additional resistances do as you say, add a level of headroom.

I have always thought load tests as a measure of mod performance were a pointless
activity, unless you are just going to use them to calculate the actual performance
of you mod and look at the device resistance. But the vaping reviewers never do the maths.