Stress on IMR Battery Question

[Gummy Bare]

Can a 18350 IMR battery take the stress of a .5ohm coil safely? I've been getting into sub-ohm coils with my mech mods, but I'm not sure how low I can safely go. I made a .5ohm yesterday and it hits real nice, but I'm just worried it's too low for the battery.

One of the 18350 batteries I was using got to the point where it would not fire any more after a few hours of use, not sure if that means it got drained low, or if I killed it.

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[jasl90]

The only way to know for sure it to find a data sheet for your specific battery and find out what it maximum C rating is.
So say for example the max C rating for a 700 mAh battery is 8C... Max amp draw would be 5.6 amps.
Assume 4 volts on a freshly charged battery... 0.5 ohms would draw 8 amps.

On the bright side, IMR batteries tend to just die with whimper... Not a bang.

 

[pAth77]

Here is a graph showing the results of a test performed by David over at SuperT. I reposted it before in a different thread, but I couldn't remember which one so I grabbed it from the SuperT subforum. It shows perfectly how much the AW IMR 18350s can handle. These were continuous load tests, which puts the batteries through much more abuse than we do while vaping. The most impressive result is the max temp that the battery reached during a continuous 10amp draw!!!

 

[Gummy Bare]

Well, most of the 18350's I have are not AW's, so it sounds like a .5ohm might be a bit too low for them to run safely. The battery that stopped firing didn't get hot and didn't vent at all. I charged it in a lipo bag and it seems to work fine again. But I've never seen a IMR just stop working like a protected battery does, so I guess that a good sign that my coil is to low... unless I don't fully understand how an IMR functions.

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[Gummy Bare]

The only way to know for sure it to find a data sheet for your specific battery and find out what it maximum C rating is.
So say for example the max C rating for a 700 mAh battery is 8C... Max amp draw would be 5.6 amps.
Assume 4 volts on a freshly charged battery... 0.5 ohms would draw 8 amps.

On the bright side, IMR batteries tend to just die with whimper... Not a bang.

I don't know much about current, amps, ex. What math are you getting the amps a particular coil will draw? Also, is the max C rating of a battery based on a constant drain or load? So when using it on a APV with only 2-5 second bursts, you could exceed the normal limit?

Sorry, I'm a little lost here.

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[Kemosabe]

Gummy- i dont have the C rating of your battery, but once you determine it, here is the formula:

Max drain rate in amps is C in mAh / 1000 x C rating

Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply 8 times the capacity). Therefore the max discharge current in amps is:
600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
= 4800 / 1000
= 4.8 amps

 

[Gummy Bare]

Gummy- i dont have the C rating of your battery, but once you determine it, here is the formula:

Max drain rate in amps is C in mAh / 1000 x C rating

Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply 8 times the capacity). Therefore the max discharge current in amps is:
600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
= 4800 / 1000
= 4.8 amps

Thanks, I don't think I'll find the C rating of the batteries I have... well, as far as my 18350's go. All my 18650's and 18500's are efest. But my 350's are just the generic text blue and reds you see around.

I need to get some better 350's... for a long time I've been using VV/VW mods, so I didn't need to know much about my batteries. But now with the mech mods I got and the sub-ohm coils I like in trying to figure out more. Like I said, the .5ohm coil ran amazing... but I'm trying to be safe. I don't wanna assume everything is fine just because it's working. I need to see if I can adjust my 18350 mod enough to fit my short stop chip in there... the short stop will stop working if my battery can't hang with the load right?

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[Kemosabe]

yes, i beleive thats how the shortstop functions. personally i have a kick in my mech so i dont know for sure.

upgrading all your batts to IMR will be well worth it.

 

[Euphonious Nonsense]

Yes that is how the shortstop works sir.

 

[Gummy Bare]

yes, i beleive thats how the shortstop functions. personally i have a kick in my mech so i dont know for sure.

upgrading all your batts to IMR will be well worth it.

Their all IMR, just not AW.

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[fanatic205]

I sometimes use efest 18350 when im out and a bout on .6 ohm setup. They get the job done but they dont last long on SLR builds , i can tell a difference even off the charger compared to 20amp 18650, but yes 18350 will do fine on SLR.

 

[pdib]

So, IMR batts aren't going to explode in your face, Gummy. They are going to get hot. Yes, the C rating is for continuous discharge (not pulse discharge). Most good 18350 batts are technically insufficient for .5Ω. Here's where you figure out what amperage your setup is drawing. (I use 4.2 volts, as that's the highest I can do on a fresh battery) Ohm's and Joule's Law Calculator. When considering safety, think about pocket or purse discharge (that would be continuous).

 

[Gummy Bare]

I sometimes use efest 18350 when im out and a bout on .6 ohm setup. They get the job done but they dont last long on SLR builds , i can tell a difference even off the charger compared to 20amp 18650, but yes 18350 will do fine on SLR.

So, IMR batts aren't going to explode in your face, Gummy. They are going to get hot. Yes, the C rating is for continuous discharge (not pulse discharge). Most good 18350 batts are technically insufficient for .5Ω. Here's where you figure out what amperage your setup is drawing. (I use 4.2 volts, as that's the highest I can do on a fresh battery) Ohm's and Joule's Law Calculator. When considering safety, think about pocket or purse discharge (that would be continuous).

Thanks for the info guys... and I always make sure the mod won't fire in my pocket. I don't use a purse, since I'm a guy and I don't live in France, lol. Guess my screen name is a little girly, but what can I say... I like my candy.

Time to make some more low ohm attys and buy some AW batteries (and some candy wile I'm at it).

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[pdib]

Efest are just as good and cost less, IMHO. I still like MNKE 18650 best. (Nice purse, BTW, Frenchie)

 

[Kemosabe]

Their all IMR, just not AW.

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oh, right. i think itll still make a difference though.
i recently just got some Efests. previously i had only used AW, but im liking these Efests.

 

[Gummy Bare]

Efest are just as good and cost less, IMHO. I still like MNKE 18650 best. (Nice purse, BTW, Frenchie)

Good to know... I've never owned any AW's, but everyone seems to jock them all the time. Just made a .6ohm coil, here's the little cheap set-up I got for a stealth 18350 to bash around with (I don't like to take my EA mod out of the house much, lol).



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[Kemosabe]

Efest are just as good and cost less, IMHO. I still like MNKE 18650 best. (Nice purse, BTW, Frenchie)

is the MNKE chemistry available in sizes other than 18650?

 

[Gummy Bare]

How low is a safe drain on a IMR? I thought 3.2 volts, but I just read somewhere where it was saying the 2.2-2.5v rang.

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[WillyB]

Here's where you figure out what amperage your setup is drawing. (I use 4.2 volts, as that's the highest I can do on a fresh battery) Ohm's and Joule's Law Calculator. When considering safety, think about pocket or purse discharge (that would be continuous).

You don't use 4.2V with a calc like that. You need to determine the actual, vaping volts while under load, then use that number + your measured resistance to determine the AMP/current draw and vaping watts.



For all you subΩ 18350 users the AW IMR18350 seems like a much better choice over the Efest.

AW vs. Efest

Click to the 5A trace.

The AW sags less and maintains a higher voltage longer. If you put a pencil to it the AW will be providing about ~12% more watts than the Efest.

 

[pdib]

is the MNKE chemistry available in sizes other than 18650?

nope. . .........