Why I Come Down On Certain Batteries.

[Ripshod]

I'm gonna try and keep this simple, although the fact is it isn't. What I'll attempt is to condense all the info into bite sized chunks that are easy to digest.

There are lots of new cells appearing making wild discharge current claims. So what I'll do is take one specific cell (the AWT 40Amp 2600mAh 18650 from Gearbest) and show you why it won't do what we're lead to believe by numbers.

So, the cell itself:

Specification :

Size : 18.20mm x 65.05mm
NominalVoltage : 3.70V
Nominal Capacity : 2600mAh
Charging Method : CC/CV 4.20V
Discharge Voltage : 2.50V (Average Cut Off)
Charging Current CC : 1250mA
Rapid Charging Current : 4000mA
Continuous Discharge Current : 35A
Max. Short Peak Discharge CC : 40A
Weight : 60gr.max
Colour : Yellow , Black
Version : Flat Top
Protection : No

Looks good eh? Well, frankly no. I'm used to the maths so straight away I can see one warning. Take lines 8 & 9, the continuous and maximum currents. To my eye they're too close together.

eg, take the LG HE4. Continuous Current 20Amps, Peak Current 35Amps. Peak is Continuous + 75%
Take the VTC4. Continuous Current 30Amps, Peak Current 60Amps. Peak is Continuous + 100%
So we can see the difference is quite large.

AWT. Continuous Current 35Amps, Peak Current 40Amps. Peak is continouous + 14%.
That result is not expected. I'd expect any Li-Ion cell to have a Peak at least 35% over the Continuous. Straight away this got me interested in the truth.

So I went on a hunt last night and read through a few reviews. Some were obviously biased for or against this cell, so ignoring them I found a good review from a trusted source. It's actually the same source I got the specifications from:

Testing Results :

Tested Capacity : 2580mAh , 15A CC Discharge test , 97.3% of Claimed Capacity
Measured Energy : 7.939Wh (Discharge Test)
Test Discharge Time : 14:36 min (10A Test)
Battery Temperature : 37.0C by 10A Load
Internal Resistance (DC) : 0.04-0.05 Ohm
Battery Rate : 15C

I wouldn't expect ANYONE to see what's wrong here. Someone with a grasp of Ohm's law would stand a 25-30% chance of spotting it. I work with Ohm's Law every day so I see it like a 100Watt lightbulb in a room with no windows.

Internal Resistance : 0.04-0.05 Ohm

Why? Let's say we use this cell at 20Amps. I'm not saying it won't deliver, but what does happen by the laws of physics when it does is quite a shock.

So, V=IR = 20x0.04 = 0.8Volts. If the fresh cell has a voltage of 4.2Volts, when fired at 20Amps the Volts drop to 3.4 instantly.
Okay. This is supposed to be a 35Amp cell, so 35x0.04 = 1.4Volts. So the Volts drop to 2.8. We're bordering on battery homicide here now, that's right on the limit.

Now - the shocker - POWER.
Straight to the crux of it.
at 35 Amps Power = I²R = 35²x0.04 = 49 Watts. That's 49Watts of HEAT being generated inside the cell. That bugger is gonna heat up like a roman candle.

All this would have been worse if I'd used 0.05Ohms for the Internal Resistance.

This stuff isn't all about Current/Capacity - and I'm glad I know enough to spot things like this.

Vape Safe!!

[Roscopecotrain]

Ripshod i can't say i understand much of your post but for newer vapers do you have a list of batteries that are good?

I only use xtar which are re branded sony, samsung 25r and the lg ones.

[Ripshod]

Good idea Roscopecotrain.

I think I'll get together with VapingBad and compile a list of the better batteries and their power limits, rather than amps. A chart with the figures listed rather than having to be calculated would make things easier for everyone - as well as safer
I don't think we'll be able to include rewraps though, sources can change like the weather.

[igual]

I think that a battery list would be great with maybe safe build limits/capabilities etc.
As we all know from YouTube video etc a little knowledge makes peeps dangerous.

[Ripshod]

Get involved peeps. Add batteries you'd like to see listed here!!

[Die5el]

Im glad i bought 8 GENUINE SONY US 18650 VTC5 IMR 30A from ecoluxshop in august last year i paid £16.59 for 2, use them in all my mech mods that uses 18650 you got to be do careful on what batteries you use.its a pita trying to get hold of them now.

[Perpetua]

People are too swayed by price when it comes to buying batteries ( I think ) better to pay a little more for some that are fit for our purposes and safe!

A list with recommended batteries and their best known sources sounds like an excellent idea to me.

[Roscopecotrain]

May 23, 2015 10:12:30 GMT Perpetua said:

People are too swayed by price when it comes to buying batteries ( I think ) better to pay a little more for some that are fit for our purposes and safe!

A list with recommended batteries and their best known sources sounds like an excellent idea to me.

I agree perps although i can get a pair of samsung 25r or pair of vtc4 for just £9.99 at my local vape shop. To me that is not expensive and you are still getting great batteries.

[Perpetua]

May 23, 2015 10:15:30 GMT Roscopecotrain said:

May 23, 2015 10:12:30 GMT Perpetua said:

People are too swayed by price when it comes to buying batteries ( I think ) better to pay a little more for some that are fit for our purposes and safe!

A list with recommended batteries and their best known sources sounds like an excellent idea to me.

I agree perps although i can get a pair of samsung 25r or pair of vtc4 for just £9.99 at my local vape shop. To me that is not expensive and you are still getting great batteries.

True enough Ros that's a great price . . . . though you'd hope that a shop selling vaping equipment/accessories would only be selling suitable batteries. I was thinking more of those cheap and not so cheerful batteries that are available on the likes of Ebay that are all too easy to pick up for someone who doesn't understand the implications of using them.

[Ripshod]

May 23, 2015 10:20:46 GMT Perpetua said:

I was thinking more of those cheap and not so cheerful batteries that are available on the likes of Ebay that are all too easy to pick up for someone who doesn't understand the implications of using them.

You are sooooo right there.

I originally posted this because I felt it could appear so pompous when I jump on a thread about batteries giving my advice.

So glad I posted now, it seems like something good will grow from this

[Perpetua]

May 23, 2015 10:29:42 GMT Ripshod said:

May 23, 2015 10:20:46 GMT Perpetua said:

I was thinking more of those cheap and not so cheerful batteries that are available on the likes of Ebay that are all too easy to pick up for someone who doesn't understand the implications of using them.

You are sooooo right there.

I originally posted this because I felt it could appear so pompous when I jump on a thread about batteries giving my advice.

So glad I posted now, it seems like something good will grow from this

Definitely.


Personally, I've not got a scooby about batteries - so any that I've bought have been from forum recommendations or from Vendors who I know wouldn't sell fakes and have done their research first before stocking them.

[chrisjw]

Great thread & great idea...............



"Life...........is just a bowl of tricks!!!!!!"

[svenson1]

I agree. I always buy from reputable suppliers to make sure they are genuine products. That said, I would really like to see a list of batteries complied by trusted fellow vapers with the knowledge that most of us don't.
Thanks loads.

[vaporsizer]

Thanks for the op & the idea of a safe battery list is a good one too.

[demondog13]

Superb thread Ripshod, whilst I don't fully understand ohm's law, I do trust yourself and VapingBad in this area, all my batteries have been purchased from those recommendations and from trusted vendors associated with this forum. Keep up the good work in helping us vape safely.