Time for Pulse Discharge!

[Shinyobjects]

Disclaimer: Please no one try what I'm about to describe. While it may be listed as safe on a website, I know enough to know that this is pushing the limits much further than they need be pushed. I just don't want to get anyone killed...

Hey guys,

Quick question for anyone who may happen to know. A lot of batteries are rated (either by manufacturer or reseller or battery tester or whomever) for safe pulse discharge amps for a prescribed maximum amount of time. For example, the Battery Bro website lists the following information for the Samsung 25R: "Safe pulse discharge ratings: 95A < 0.5 sec, 65A < 1 sec, 40A < 5 sec, 30A < 6 sec."

Personally, I never sub my ohms (cute phrase, huh?) below 0.4 on mech mods so I will never have to worry about these ratings in practice but I am interested about them in theory. Let's assume that this information is accurate and it is perfectly safe to pulse 95A (my god that's intense, lol) for less than half a second. My question is this: how long in between pulses will any daredevil crazy enough to attempt this need to wait before attempting the next pulse? Will either the safe pulse duration or the time in between pulses decrease as this hypothetical but brave individual continues their death-defying practice? (I assume even if safe this wears on battery more than amperage levels below the continuous discharge rating.)

Thanks in advance!

 

[DIY FancyLights]

General theory says that the avg current must still be below the pulse current vs. time. From a practical aspect I would say it needs to be more then twice that. There are chemical & thermal factors that need to be accounted for. I'm not a thermal engieener, but the heat generated from such a high current pulse needs time to disperse or you risk some of the same issues or worse from a high avg current. The last thing you want is an Li-ion over heating in front of your face! SAFETY FIRST.

Considering how many batteries overrate what they can candle I strongly recommend people ignore the pulse ranting and are conservative even on their battery rating unless it is name brand from a very trusted source!!! There are so many fakes or overrated batteries, rewraps, etc YOU DO NOT WANT TO TAKE ANY RISKS!!!!

 

[Shinyobjects]

Wow super fast reply, thank you! So basically, if I understand this right, if a battery is rated for 20 Amp continuous discharge and one wished to pulse at twice that (40 Amps), theory would dictate that 50% of the time can safely be spent pulsing, as long as the "40A < 5 sec" rule from above is followed?

And personally I am too afraid to go much over half the continuous discharge rating because I get paranoid (for example I'm always worried my ohm reader is reading higher than it actually is and other things like that lol). Really just interested in the theory.

 

[jwill]

Pulse ratings are garbage and a good way to just wear out or pop batteries. CDR is the only value that actually means anything. If you know what you are doing you can stretch the limits how you feels safe, but generally speaking the pulse values mean nothing in the real world.

 

[jwill]

Welcome to VU by the way.

 

[DIY FancyLights]

Good specs will specify what the maximum pulse interval is, but you do still have to watch the thermal characteristics as well. Many batteries as I said lie about what they can handle or don't give the proper ratings or enough info.

As I said, ignore that specification in trying to design anything.

For non-battery parts, the pulse ratings they give are significantly higher the the normal ratings, but in the fine print say for non-repeating pulses ... so they aren't even accounting for thermal effects for those parts.

 

[DIY FancyLights]

Pulse ratings are garbage and a good way to just wear out or pop batteries. CDR is the only value that actually means anything. If you know what you are doing you can stretch the limits how you feels safe, but generally speaking the pulse values mean nothing in the real world.

Maybe I should have been more negative in my reply as well I was trying to convey warnings & extreme caution without scaring anyone silly.
Batteries have a habit of failing in spectacular ways !

 

[Shinyobjects]

Thank you for the welcome jwill! I've been reading for years but this is only my second post.

And yes guys I agree, batteries are scary. I always err on the side of caution with mech mods. The last thing I want to end up as is the next horror article on the dangers of vaping (nor would I want anyone else to end up that way because of me, hence my initial disclaimer lol).

 

[jwill]

Maybe I should have been more negative in my reply as well I was trying to convey warnings & extreme caution without scaring anyone silly.
Batteries have a habit of failing in spectacular ways !

It wasn't negative, just true. An experienced person can push a batteries limit if they know what they are doing, is it advisable? Not really, doable sure. Measuring by pulse ratings is a sure fire way to just have to buy more batteries and the 25r's are good batteries if used within specs. These particular batteries do not like being overclocked. This is a case of needing the right tool for the job.

 

[Ralph_K]

I was vaping on a pulse bf mod with a .08 build used Ijoy 20700 and Golisi S35 21700. One of the Ijoy batteries died after a few days but that was kind of expected

 

[chrisakasparky]

I was vaping on a pulse bf mod with a .08 build used Ijoy 20700 and Golisi S35 21700. One of the Ijoy batteries died after a few days but that was kind of expected

That’s really dangerously low resistance.

 

[PoppaVic]

Happily, people remain edible and biodegradable.

 

[DIY FancyLights]

Happily, people remain edible and biodegradable.

I'll pass on the edible, but encourage the biodegradable or combustible.

 

[PoppaVic]

Donner Party BBQ & Grill.

 

[triakis]

Pulse ratings in electronics typically deal with millisecond durations. You're not capable of pressing the button and releasing it that fast. When you're discussing 1-5 seconds that's intermittent duty and the current ratings, while higher than continuous current draw, are certainly going to be nowhere near the seeming stratospheric published pulse ratings.

 

[The Cromwell]

I doubt if Samsung supports Battery Bros figures on the 25R.

 

[entropy1049]

This reminds me of an instructor in submarine school who said (I’m paraphrasing) “Crush depth is actually the manufacturers way of saying ‘We really don’t know why the submarine hasn’t imploded yet’”. This is how I think of pulse ratings.