Continuous Discharge Ratings vs Pulse (Burst) Discharge Ratings

[Baditude]

Continuous Discharge Ratings vs Pulse (Burst) Discharge Ratings

The "continuous discharge rating" in amps is the standard specification for amp limits within the battery industry. It is a determination made by the manufacturer and represents the amp limit a battery can be safely used before it will fail.

The "pulse or burst" discharge rating is not a specification standard within the battery industry. Every manufacturer or vendor seems to have their own definition of what the pulse rating is to them.

A pulse discharge rating is any use above the continuous discharge rating. It is never safe and not within the intended operating parameters of the battery. You should not operate your device above the continuous rating if you can help it. The pulse rating is a condition in which the battery is on basically a buildup to failure. It is exceeding the sustainable and intended discharge rate of the battery. It is inappropriate for a consumer device to operate in the pulse range of its battery.

Which would be why we shouldn't rely on any pulse rating. Any failure, mechanical or electronic, that fires the mod will operate in the 'continuous' mode. If your setup relies on a pulse rating, it's instantly over spec.

If your amp draw is safely in the continuous discharge range, your coil could act almost like a fuse and burn out before the battery is stressed. If you are already running the battery at the edge of it's limits (pulse), there is no margin of safety.

Anyone who is sub-ohming below 0.2 ohms are operating on the pulse rating, and are operating over spec for any 18650 battery currently on the market.

Sony US18650VTC5 2600 mAh High Discharge Flat Top

Specifications:
Nominal Capacity: 2600 mAh
Minimum Capacity: 2500 mAh
Nominal Voltage: 3.6V
Discharge End Voltage: 2.5V
Standard Charging Current: 2.5A
Charging Voltage: 4.20+-0.05V
Max. Continuous Discharging Current: 30A
Internal Resistance: 13.5 milli-ohms​

1.0 ohm = 4.2 amp draw
0.9 ohm = 4.6 amp draw
0.8 ohm = 5.2 amp draw
0.7 ohms = 6 amp draw
0.6 ohms = 7 amp draw
0.5 ohms = 8.4 amp draw
0.4 ohms = 10.5 amp draw
0.3 ohms = 14.0 amp draw
0.2 ohms = 21.0 amp draw
0.1 ohms = 42.0 amp draw ----> OVER BATTERY SPECS
0.0 ohms = dead short = battery goes into thermal runaway


"Sometimes, just because you can, doesn't mean you should." -- PBusardo

 

[Bunnykiller]

My sentiments exactly..... pulse rates are pretty much ficticious, unfounded, not certified and eventually will be the demise of alot of good batteries....

now if the manufacturers could make batteries that fail less violently...... just simply quit working...

 

[Susan~S]

Thank You -- for posting this!!



(Hope you don't mind. I snatched this animated gif from another post of yours! Love your latest blog post: Purple Efest Batteries not as Advertised

 

[Asbestos4004]

Nice work, Bad! I really appreciate you taking the time to post it.

 

[dr g]

hey i recognize some of those remarks

 

[Nytebreed]

[SARCASM] But the American Association of Plastic Surgeons told me it was OK to rely on the pulse rate of the batteries.[/END SARCASM]
Discalimer: This did not actually happen.

As always Good post Badditude.

 

[Baditude]

hey i recognize some of those remarks

Hey, consider it a compliment that I borrowed some of your wording from a previous post on this subject matter. I couldn't have said it any bettery than you did, so I used your statements. You don't mind, do you?

 

[Ryedan]

Bookmarked for future use

 

[dr g]

Hey, consider it a compliment that I borrowed some of your wording from a previous post on this subject matter. I couldn't have said it any bettery than you did, so I used your statements. You don't mind, do you?

I don't mind, though generally if you are going to utilize someone else's words verbatim you probably want to at least let them know.

 

[K_Tech]

The "pulse or burst" discharge rating is not a specification standard within the battery industry. Every manufacturer or vendor seems to have their own definition of what the pulse rating is to them.

If I may be allowed to expand on that a little;

Taking the VTC5 as an example, Sony came up with its pulse ratings based on temperature rise. XX amps for XX seconds raises the temperature of the battery to 100C. (I think its highest example was 80 amps for a few seconds).

Now, it's all well and good that Sony went through the trouble of doing that, but even at that relatively "low" temperature (hey, at least it's not at thermal runaway, right?) damage is occurring internally at a microscopic level.

It's like running over red line on an engine. You KNOW something bad is happening, you can't see it, and if you keep doing it, your engine WILL fail.

Maybe next week. Maybe next month. But every excursion over the CDR is damaging that battery a tiny, tiny bit at a time.

 

[Ryedan]

If I may be allowed to expand on that a little;

Taking the VTC5 as an example, Sony came up with its pulse ratings based on temperature rise. XX amps for XX seconds raises the temperature of the battery to 100C. (I think its highest example was 80 amps for a few seconds).

Now, it's all well and good that Sony went through the trouble of doing that, but even at that relatively "low" temperature (hey, at least it's not at thermal runaway, right?) damage is occurring internally at a microscopic level.

It's like running over red line on an engine. You KNOW something bad is happening, you can't see it, and if you keep doing it, your engine WILL fail.

Maybe next week. Maybe next month. But every excursion over the CDR is damaging that battery a tiny, tiny bit at a time.

You're talking my language K_Tech . I'm an old gear head from way back who got into souping up cars to make them go faster. Go figure right, LOL.

An engine has a cruse redline and a shift redline. The cruse redline is the RPM at which the engine will make so many revs (or miles) before it wears out. The shift redline in a well built engine is the RPM at which engine parts will break because the parts have been stressed past what they can handle. Does this sound familiar yet

This stuff is very well understood for car engines, but not at all defined for our batteries. At least not as far as I know. There is no defined standard I know of for continuous amp discharge much less for pulse ratings. It's not good because it leaves us guessing, but it is what it is.

 

[KenD]

Thanks for this Baditude. There should be a script that automatically posts that text whenever "pulse rating" is mentioned on this forum.

I'd add that in addition to all the other problems with relying on pulse discharge ratings no one seems to pay any mind to how long a pause there's supposed to be between pulses. For example, 10 seconds on and 10 seconds off probably qualifies as continuous discharge.

 

[Karnn]

I gotta say I have been a long time lurker and I've always liked your posts Baditude, as someone who likes to build low ohm coils I keep stumbling on your posts and you are always a voice of reason, good looking out for others man

 

[windxrunner]

some guy was asking me about what his battery can do and what builds he can make, i gave him a quick run-down, told him to get an accurate ohms meter, and linked him to this page.

 

[Nytebreed]

Let's see if graphical aids will help those that still don't get it.

CONTINUOUS DISCHARGE RATE


PULSE DISCHARGE RATE