18650 Purple Efest 35amp Battery Quesion

[Huggett]

Purple EFests are IMR and are NOT protected. So no they won't cut out, you'll notice a large drop off in vape quality around the time they get to 3.3v though which is when you need to change them.

also you can't go anywhere close to 0.01ohms with those batteries. 0.01ohms at 4.2v requires 400(four hundred!) amps.

you can safely use them down to about 0.15ohms.

If you're sticking to 1ohm+ coils then the normal red Efest batteries will be plenty good enough.

Yeah I checked the ohm calculator after I posted that. Damn google lied to me, who would have thought someone on the Internet lied lol?

When the voltage starts to drop, doesn't it then effect the ohms? I mean at full power its safe but as it starts dropping it becomes dangerous?

I know it wont effect it at 1ohm but say I started sub ohming at some point in the future?

Sent from my GT-I9300 using Planet of the Vapes mobile app

 

[VaperCaper]

Volts and ohms aren't really related like that.

The battery puts out a set voltage. As the battery discharges this voltage gets less and less. Also the device you're using has an internal resistance which reduces the amount of volts getting to the coil. when you buy a very expensive mod, one of the reasons it's expensive is because it uses good quality internal components that deliver more of the volts from the battery to the coil.

A freshly charged batery is 4.2volts and it'll drop to about 3.5volts before it gets too weak and you'd swap it for a fresh one.

The ohms of the coil combined with the voltage determine the power and the amount of current needed. (power is in watts, current is in amps)

As the coil heats up it's resistance (ohms) can change a bit, but not by a lot. So as your battery discharges in a mech the amps required and the power output decrease but the resistance of the coil stays the same all the time. It uses the highest current (amps) when the battery is fresh.

If you want to maybe play with sub ohm coils later on then buying the purple EFests (or a n other decent battery) is a good investment.

 

[Tubbyengineer]

Yeah I checked the ohm calculator after I posted that. Damn google lied to me, who would have thought someone on the Internet lied lol?

When the voltage starts to drop, doesn't it then effect the ohms? I mean at full power its safe but as it starts dropping it becomes dangerous?

I know it wont effect it at 1ohm but say I started sub ohming at some point in the future?


Sent from my GT-I9300 using Planet of the Vapes mobile app

The resistance of a coil is fixed at the time of construction (wire thickness, number of turns & diameter of turns) the wattage is determined by resistance and voltage, as voltage drops so will the wattage - as long as the coil is safe when you start to vape it should remain safe (barring someone fiddling with it) until the battery requires changing.

 

[B1mble]

A coil is not a constant power device, the power output of the coil goes down every second you use it. If it were a constant power device the current draw would go up as the voltage went down.

Almost every metal actually rises in resistance as it heats up. Which is why lightbulbs of the incandescent persuasion almost always fail at switch-on. Their resistance is lowest when they are cold and so the current is highest. It's the same with a coil, as it heats up its resistance rises. How much this happens with Kanthal I have just looked up and it is negligible at the sort of temperatures involved in vaping. Or 1% increase at 500C.

My 0.2 ohm Prometheus is drawing 9.9A at a load voltage of 3.1V or 30W. Off-load the cell is measuring at 3.98V. With the ammeter removed, it is measuring 3.5V (36W)under load so will be pulling more than 10A. So I'll vape on it for a bit and remeasure. This is using an LG cell which is what I believe to be inside the purple Efest wrapper.

To be continued

 

[B1mble]

It's time I bought some shunts so I can reliably measure higher currents. The room is rather foggy now and the atomiser is too hot to touch. It's now reading 3.36V under load 3.7V off load. I'm trying to use up the charge as quickly as possible but it is complicated by the 4" drip tip burning my lips. Time to swap drip tips. I'm essentially using this Prometheus clone as a dripper(It's a Genesis), dry hits at these power levels aren't pleasant. I'm also mildly OD'd on nic. Oops, another dry hit, I'm essentially vaping what's on the deck. I'd not normally use it this way, I'm just trying to flatten the cell quickly. Down to 3.14V under load and I can tell the difference in the vape. Let's see what the current is:

Off-load voltage 3.6V, draw 9A or about 32W. Remember that the act of measuring the current is reducing it unless you have fancier gear than I do.

I regard lithium cells as flat at 3.6V, there's not a lot left at such heavy current draws. The cells can go down to 2.5V but there is no reason at all to do so. When I start to notice a change in the vape, it's time to charge the cell. Obviously in higher resistance atomisers this would take longer which is why I chose that one to do these measurements with.