Battery amp advice

[zoiDman]

...

Yup, that's what I do too

Here is another thing about batteries that I Don't Understand. And that is when they say "Continuous" and "Peak" Amps.

The Continuous park I get. Or At least, I Think I get. But the "Peak" always makes me Raise my Left Eyebrow.

Does Peak mean that I can do it ONE Time Safely? And then the Next Time I do it I could be Holding a Bottle Rocket? How Many Times can a Battery Draw Peak Amps?

And does the Continuous and Peak Amps change as the Battery Gets Old? Or from Thermal Stresses of Charging or Usage?

 

[Ryedan]

Here is another thing about batteries that I Don't Understand. And that is when they say "Continuous" and "Peak" Amps.

The Continuous park I get. Or At least, I Think I get. But the "Peak" always makes me Raise my Left Eyebrow.

Does Peak mean that I can do it ONE Time Safely? And then the Next Time I do it I could be Holding a Bottle Rocket? How Many Times can a Battery Draw Peak Amps?

And does the Continuous and Peak Amps change as the Battery Gets Old? Or from Thermal Stresses of Charging or Usage?

I should have done a couple of experiments with my old MNKEs before I completely discharged and retired them. I had run them for a year and a half and their voltage drop under load had gone from 0.4V to almost 1V at 0.5 ohms. I think I had a couple of hundred charge cycles on them.

As I understand it, that voltage drop is from internal cell resistance and the higher the cell resistance the more heat the cell generates during discharge (and charge). This tells me that maximum amp rates will go down, both continuous and pulse, or peak. That's why I occasionally check voltage drop on my batteries.

But I've never seen any data on this, it's just my opinion about how I think it works.

Anyone have any info, thoughts or opinions on this?

 

[Midniteoyl]

Hopefully they do. That, or the End User Should to be Safe.

Because if I Sample 100 Batteries and 50 are 25A and 50 are 35A, then I could say that Statistically, they are 30A Batteries.

No... If they test 50% at 25amps, then those are the ones that get rejected and sold off as 20's by another 'fire' company... that is the limit they set or go back to the drawing board and find out why they dont do 30 like they thought.

 

[Midniteoyl]

Here is another thing about Batteries that I Don't Understand. And that is when they say "Continuous" and "Peak" Amps.

The Continuous park I get. Or At least, I Think I get. But the "Peak" always makes me Raise my Left Eyebrow.

Does Peak mean that I can do it ONE Time Safely? And then the Next Time I do it I could be Holding a Bottle Rocket? How Many Times can a Battery Draw Peak Amps?

And does the Continuous and Peak Amps change as the Battery Gets Old? Or from Thermal Stresses of Charging or Usage?

It all has to do with heat... They can go 30amps continuously because they dont get hot enough at that amperage to cause problems. They can go up to a 'peak', say 60amps in the VTC5, for short periods, like 10 secs, until the heat starts to become too great and starts breaking down the battery. That said, it doesnt mean you can constantly hit the 'peak' over and over as that will shorten the life of the battery. The more you do it, the less 'peak' it can start to handle and sooner or later the battery will be damaged.

 

[Midniteoyl]

Battery manufacturers list whatever battery specs they wish to. Some companies understate their specs, some overstate their specs.

For instance, Efest lists their purple 18650 2500mah battery as a 35 amp battery. Tear the purple wrapper off and the cell says it is a re-wrapped LG18650HE2 battery -- LG lists the same cell as only a 20 amp battery. So who are you going to believe? The company who actually makes the cell, or the company who is just rebranding it? For people who are doing extreme sub-ohm vaping, those missing 15 amps could be critical.

Efest 30 & 35 amp batteries

Quoting Dampfakkus.de:

Im finding its not eFast that is the problem here so much as they state the batteries as '20amp continuous, 35amp peak'. Its the retailers that are saying they are '35amp'. Now, eFast isnt helping by listing '35amp' on the casing, I agree...


Efest 18650 2500mah 35A IMR

18650
2500mah
20A continuous discharge
35A max pulse discharge
18.23mm diameter
65.11mm length
3.7V
unprotected
flat top

 

[Baditude]

Im finding its not eFast that is the problem here so much as they state the batteries as '20amp continuous, 35amp peak'. Its the retailers that are saying they are '35amp'. Now, eFast isnt helping by listing '35amp' on the casing, I agree...


Efest 18650 2500mah 35A IMR

18650
2500mah
20A continuous discharge
35A max pulse discharge
18.23mm diameter
65.11mm length
3.7V
unprotected
flat top

Efest is intentionally confusing continuous discharge rate (the industry standard spec for amp output) with the peak or pulse discharge rate. IMHO this is a deceptive business practice by Efest just to make their batteries to look better than their competition. Consumers will see the 35 amps printed on the purple battery casing and compare that spec with the continuous discharge rate with other brands. It's not fair and its not right.

 

[Midniteoyl]

Efest is intentionally confusing continuous discharge rate (the industry standard spec for amp output) with the peak or pulse discharge rate. IMHO this is a deceptive business practice by Efest just to make their batteries to look better than their competition. Consumers will see the 35 amps printed on the purple battery casing and compare that spec with the continuous discharge rate with other brands. It's not fair and its not right.

Agreed.. But I wont buy from vendors that claim its a 35amp battery either. Any more than I will from the ones that claim 60amps for the VTC5


......

 

[Baditude]

Here is another thing about Batteries that I Don't Understand. And that is when they say "Continuous" and "Peak" Amps.

The Continuous park I get. Or At least, I Think I get. But the "Peak" always makes me Raise my Left Eyebrow.

Does Peak mean that I can do it ONE Time Safely? And then the Next Time I do it I could be Holding a Bottle Rocket? How Many Times can a Battery Draw Peak Amps?

And does the Continuous and Peak Amps change as the Battery Gets Old? Or from Thermal Stresses of Charging or Usage?

A Guide to Understanding Battery Specifications

• Maximum Continuous Discharge Current – The maximum current at which the
battery can be discharged continuously. This limit is usually defined by the battery
manufacturer in order to prevent excessive discharge rates that would damage the battery or
reduce its capacity.

Maximum 30-sec Discharge Pulse Current –The maximum current at which the
battery can be discharged for pulses of up to 30 seconds. This limit is usually defined by
the battery manufacturer in order to prevent excessive discharge rates that would damage
the battery or reduce its capacity.

 

[zoiDman]

No... If they test 50% at 25amps, then those are the ones that get rejected and sold off as 20's by another 'fire' company... that is the limit they set or go back to the drawing board and find out why they dont do 30 like they thought.

And this is based on.... ?

 

[Midniteoyl]

Worked in the industry...

Statistics, such as the bathtub curve, works for predicting the rate of failures and setting the warranty, but not for setting safe limits on power draw.

 

[Ryedan]

No... If they test 50% at 25amps, then those are the ones that get rejected and sold off as 20's by another 'fire' company... that is the limit they set or go back to the drawing board and find out why they dont do 30 like they thought.

Very interesting Midniteoyl. So, to make sure I get this right, you're saying the manufacturer tests every cell on a 'maximum draw tester' and separates the low draw cells from the higher draw cells. Is this correct?

Worked in the industry...

Statistics, such as the bathtub curve, works for predicting the rate of failures and setting the warranty, but not for setting safe limits on power draw.

Do you know what the criteria are for setting safe limits on power draw?

 

[Catdumpling]

And if its a good mfg'er, a generous amount of 'fudge factor' in the headroom...

Hopefully, but that's completely up to the manufacturer. One person's "fudge factor" is another person's "a bit too risky".

I've never been involved in manufacturing batteries, but I was involved in a production engineering capacity in making limit switches that shut down oil fired residential furnaces if the burner didn't shutdown when it was supposed to. This was the last thing that would stop the furnace from starting a fire in a house.

I can assure you the scenario you describe above was not how we determined product quality. Any company who would use statistics in this manner for any high risk product would be out of business very quickly.

That doesn't mean mistakes never happen. It's almost impossible to cover every design, manufacturing and end user scenario 100% of the time, but large companies are quite risk averse and do everything they can to cover themselves against law suits by making sure their products are safe to the best of their ability.

The Dreamliner li-ion battery fires is a case where something was overlooked. Probably doesn't have anything to do with the cells themselves or I think someone would have found the problem. I suspect a lot of complexity in the electronic battery control system and a lot of other electronics close by too. AFAIK they still haven't figured out what happened, or been able to recreate the problem. I don't envy the people working on this one

Didn't the Dreamliner just have another battery problem a couple weeks ago? Maybe it was something else, but I could've sworn I read something just a week or two ago about yet another Dreamliner issue.

Here is another thing about Batteries that I Don't Understand. And that is when they say "Continuous" and "Peak" Amps.

The Continuous park I get. Or At least, I Think I get. But the "Peak" always makes me Raise my Left Eyebrow.

Does Peak mean that I can do it ONE Time Safely? And then the Next Time I do it I could be Holding a Bottle Rocket? How Many Times can a Battery Draw Peak Amps?

And does the Continuous and Peak Amps change as the Battery Gets Old? Or from Thermal Stresses of Charging or Usage?

"Peak" is what I meant by "pulsed". Peak means it should be safe if it hits that number very occasionally, but by no means is the battery designed to run at that current for more than a few seconds at a time, once in a while. It's something of a safety margin the manufacturer builds into the battery, but it's not something that should be abused.

A Guide to Understanding Battery Specifications

• Maximum Continuous Discharge Current – The maximum current at which the
battery can be discharged continuously. This limit is usually defined by the battery
manufacturer in order to prevent excessive discharge rates that would damage the battery or
reduce its capacity.

Maximum 30-sec Discharge Pulse Current –The maximum current at which the
battery can be discharged for pulses of up to 30 seconds. This limit is usually defined by
the battery manufacturer in order to prevent excessive discharge rates that would damage
the battery or reduce its capacity.

It's that "...of up to 30 seconds" part that's kind of a problem. I can't remember the specific manufacturer, but I've seen at least one spec sheet that listed the max/pulse current at 10 seconds, not 30. It's basically whatever each manufacturer decides to go with.

 

[Midniteoyl]

Very interesting Midniteoyl. So, to make sure I get this right, you're saying the manufacturer tests every cell on a 'maximum draw tester' and separates the low draw cells from the higher draw cells. Is this correct?



Do you know what the criteria are for setting safe limits on power draw?

That was kinda of a joke.. There are 'reports' of this happening in China. I dont know if they are true or not, but, the story is that some manufacturers are buying up lots and runs that failed testing and retesting them at a lower spec. If they pass, they are relabeled at the lower spec and sold off. This is the reason most recommend not buying the batteries with 'xxxFire' as name, for example.

But, yes, when I was in the industry, every single battery was tested at various charging and discharging rates according to its design specs. Those that failed where inspected to determine why and the appropriate actions were taken to correct the issue.

The 'criteria' is whatever the engineers set through the design, chemistry, and testing. This was never, however, based on 'statistics' like '50% test at 30a and 50% at 20a so lets set it to to 25a'. If it says '25a continuous', it will do at least that. All day long. If it comes from a good manufacturer. If its from an 'iffy' one, it will still do that, but maybe not for very long or will get warmer and have less 'headroom'.

Remember, Lithium batteries, in all there different chemistries, are actually very dangerous. Its only safe designs and rigourous testing and safty margins that make them 'safe' for the general population.

 

[Ryedan]

But, yes, when I was in the industry, every single battery was tested at various charging and discharging rates according to its design specs. Those that failed where inspected to determine why and the appropriate actions were taken to correct the issue.

Fascinating. I assume batteries are a reasonably high production volume item and 100% testing of charge and discharge would be expensive. Of course if it has to be done, it has to be done.

The 'criteria' is whatever the engineers set through the design, chemistry, and testing. This was never, however, based on 'statistics' like '50% test at 30a and 50% at 20a so lets set it to to 25a'. If it says '25a continuous', it will do at least that. All day long. If it comes from a good manufacturer. If its from an 'iffy' one, it will still do that, but maybe not for very long or will get warmer and have less 'headroom'.

Yes, that example of using statistics simply does not fly when it comes to a product like batteries. Most design criteria are however quantified using statistics in a way that makes perfect sense.

Are there 'iffy' battery manufacturers out there, or are you referring to companies that re-brand batteries? I thought there were not that many Li-ion battery manufactures and they were generally quite big and knew what they are doing.

 

[Midniteoyl]

Fascinating. I assume batteries are a reasonably high production volume item and 100% testing of charge and discharge would be expensive. Of course if it has to be done, it has to be done.



Yes, that example of using statistics simply does not fly when it comes to a product like batteries. Most design criteria are however quantified using statistics in a way that makes perfect sense.

Are there 'iffy' battery manufacturers out there, or are you referring to companies that re-brand batteries? I thought there were not that many Li-ion battery manufactures and they were generally quite big and knew what they are doing.

Yes, rebranders, mostly. But, as you can see in this thread, there are some manufacturers that 'push' the limits. At least when it comes to marketing.

 

[zoiDman]

If 100% Testing is Done to Batteries for certain Specs, how are things like Failure Rates or Max Amps for a Battery Determined?

Seems like Statistical Sampling would have to be Used.

 

[Midniteoyl]

The testing doesn't show if it will fail in the first 90 days.. Only empirical data can do that.

Max Amps is done through design, then testing to verify.

This aint hard guys... Heres just one way a Lithium battery can be tested. Google is your friend: Testing Lithium-based Batteries - Battery University

 

[zoiDman]

...

This aint hard guys... Heres just one way a Lithium battery can be tested. Google is your friend: Testing Lithium-based Batteries - Battery University

I always thought Google Was my Friend. LOL

But sometimes there can be a Disconnect between what is read on Google and Actual QA Standards for things like QC.

 

[DaveP]

At any rate, .13 ohms is so close to a direct short that it isn't funny. If I were high watt vaping, I'd want at least a 1 ohm cushion against an unintended catastrophic failure in front of my face.

 

[zoiDman]

At any rate, .13 ohms is so close to a direct short that it isn't funny. If I were high watt vaping, I'd want at least a 1 ohm cushion against an unintended catastrophic failure in front of my face.

I agree.

Things start to happen Very Fast when the Denominator of a Fraction approaches Zero.

A person should also have a Very Accurate way to Measure Ohms.

Check out this Sub-Ohm Chart I made in another Thread...

I had a couple of Extra Minutes so I did a Quick-n-Dirty Sub-Ohm Spreadsheet.

http://farmerengineering.com/ECF/Sub_Ohm.jpg

There wasn't much need to put much Formatting on it. Because it is Almost All in the Read.

BTW - Notice how Fast the Watts go up as the Ohms drop from .3 to .1

And how the Graph of the Watt Curve goes Vertical as the Value in the Wattage Equation's Denominator approaches Zero.