Electrical engineering question

[mcquinn]

I was studying the specs on different size Protected Lithium Ion rechargeable batteries and I found that all I have checked so far limit current to 0.5 amps .I found this interesting as everyone raves about how hot the mods are but they would be cooler than a straight passthrough.It also appears that box mods with two or three batteries in parallel would be far better than just one battery.I wonder about putting batteries in series and running the current through two of the circut boards.But the main reason I started this is
"2.5 Standard Discharge Constant current 0.2C(500mA)" cut and pasted from spec sheet for LG 18650 battery .
What does it mean 0.2C?I can decipher that it is limited to 0.5 amps.

[Royal]

Maybe this will help answer your question.

Battery discharge current

[mcquinn]

OIC C= capacity, it appears to the mathmaticly challenged that 2C would be 2xC but it is actually the capcity divided by 5.Wow this brings back MAT101 and electrical class nightmares.

[BillyBlack]

Originally Posted by mcquinn

I was studying the specs on different size Protected Lithium Ion rechargeable batteries and I found that all I have checked so far limit current to 0.5 amps .I found this interesting as everyone raves about how hot the mods are but they would be cooler than a straight passthrough.It also appears that box mods with two or three batteries in parallel would be far better than just one battery.I wonder about putting batteries in series and running the current through two of the circut boards.But the main reason I started this is
"2.5 Standard Discharge Constant current 0.2C(500mA)" cut and pasted from spec sheet for LG 18650 battery .
What does it mean 0.2C?I can decipher that it is limited to 0.5 amps.

I don't know what you mean by "Lithium Ion rechargeable batteries and I found that all I have checked so far limit current to 0.5 amps". I can assure you that my batteries are outputting far more than 0.5A. My lowly TF 14500's, when metered and while vaping, are supplying 1.6A. A standard Joye 510 ecig is supplying 1.4A.

Here is just one of many charts of amp draws at the CPF forums. This one using a specific demanding flashlight with 18650's.

SSC P7 Test , Highest to lowest ...

1. AW-IMR 2.97A
2. Trustfire 2.83A
3. UF no1 2600mAh Protected 2.67A
4. AW 2600mAh Protected 2.66A
5. Generic Blue 2.65A
6. UF 2600mAh no2 2.6A
7. UF 2400mAh Protected no4 2.45A
8. UF 3000mAh Protected no3 2.33A
9. Spiderfire 2400mAh Protected 2.3A
10. EagleTac 2.25A

I think you have misunderstood the terminology.

From Battery U.

The widely used cobalt-based lithium-ion has drawbacks; it offers a relatively low discharge current. A high load would overheat the pack and its safety would be jeopardized. The safety circuit of the cobalt-based battery is typically limited to a charge and discharge rate of about 1C. This means that a 2400mAh 18650 cell can only be charged and discharged with a maximum current of 2.4A.

[mcquinn]

TrustFire TR10440 600mAh** 3.7V AAA Lithium ion Battery with Protection Circuit
•Model: TR10440(AAA)Lithium ion AAA Battery with Protection Circuit
•Voltage: 3.7V
•Capacity: 600mAh**
•Weight: 9.5g
•With integrated PCB Protection.
•Over current protection current: 0.5A
•Over current protection voltage: 0.2V
•Over charging protection voltage: 4.25V +/- 25mV
•Over discharging protection voltage: 2.5V +/- 50mV
•Lithium Ion 10440 cylindrical rechargeable batteries.
•Lighting or other device needing 3.7V power
•Dimensions: 10.25mm x 46.25mm
It appears to say to me over current protection is set at 0.5amps.I am for sure not an expert ,which is why I asked for some clarification from someone who understands this stuff.I may very well be wrong in my understanding.

[BillyBlack]

Well you use these batteries do you think it's true? Many use the 10440's with Joye atties. If they maxed out at .5a that would mean a max of 1.1 volts.

As far as your 2 battery statement one 14500 is superior to two 10440's. Remember 'C' ratings are based on time and mAh. A battery with a high mAh rating can be charged at a higher and faster rate and by the same token can release this current faster. Hence one 900mAh 14500 is better overall (and cheaper) than two 320mAh 10440's. You'll also probably get a higher original nominal voltage. Either way a 10440 is not limited to 0.5A And remember when vaping you are using short bursts. Maybe it all means that the 10440's with a sustained, start to finish, complete to discharged state, can only provide .5A.

[Royal]

Sorry Mike, I thought the link I posted for you explained it.

Here let me try to explain,
First, in your quote, the 2.5 is only a reference number used by the place you got this data from. It has no meaning here.

Now, in this case we are using 0.2C at 500milliamps. So if 500 milliamps is applied as a constant current, the battery will be fully discharged in 5 hours. 5 hours times .5 amps equals a rating of 2500mah. or 2.5 amp hours.

So what they are doing, in laymens terms, is applying .5 amps of constant current, and timing the length of time it takes a fully charged battery to reach it's cut off, which is at 3.0 volts. This cut off is considered to be fully discharged. Once this has been calculated they can come up with the rating in milliamp hours, or larger batteries would be in amp hours.

For this battery they obtained a rating of 0.2C, in this case equals 500 milliamps, times 5 hours of constant current equals a minimum 2,500 milliamp hour rating or 2.5 amp hours.

So 0.2C is 1/5 of 1.0C and if 500 milliamps equals 0.2C, then 1.0C would equal 2500 milliamp hours maximum charge current.

I think for the 18650 the maximum discharge current is rated at 1.5C which would be 2,500 (1.0C) times 1.5C equals 3750 milliamps. So to answer another question, the 18650 can handle a load of as much as 3.75 amps. This is 7.5 times the standard of 0.2C that was used to rate the battery. 1.5C/0.2C= 7.5

So as you can see, the 500 milliamps you refer to in your quoted formula is not the total amount of current the battery can apply, but merely the load used to obtain the mah hour rating.

Heavier loads can decrease this mah hour rating as it also effects the recovery rate of the battery and drops the battery's peak voltage level at a faster rate.

Li-Ions have greater recovery time than many other types of batteries and can handle higher currents as well. The way we use them with loads lasting only a few seconds at a time, it is really hard to calculate any other variables in to the equation. So for our purpose, and since our load time is in relatively short bursts, and given the Li-Ions ability to recover, simply using the standard Mah rating should be enough to get us in a ball park range of how long we can expect a battery to last.
But for consideration, given the other variables not discussed, we can expect some slightly shorter use times.

I hope I explained it right, and did not confuse anyone any further.

[mcquinn]

I am sure you both did a good job of explaining it.Some things just make my head spin.I do use 10440's but I ended up removing the PC boards as the surface mount connection to the positive terminal broke loose on most of them and they would work intermittantly.It would appear then from what you guys are saying that any of those cells will more than deliver the goods.And whoever wrote the spec's for the 10440 I cut and pasted above could have been a little clearer.I guess it is best they do not post specs as someone might misinterpet them and start a thread in a forum.

[jcamacho]

Just received new 18650 battery from Nhaler that claims to be high drain battery, honestly I don't see the difference between this and my other 18650 batts. What are they supposed to do? There's no difference in performance but I'm going to see how long it lasts.

[Rick]

Originally Posted by jcamacho

Just received new 18650 battery from Nhaler that claims to be high drain battery, honestly I don't see the difference between this and my other 18650 batts. What are they supposed to do? There's no difference in performance but I'm going to see how long it lasts.

What's the stated mah of the two? Although batteries might have the same number, they don't always have the same mah reading, and that is what counts, the number is merely the size of the battery e.g 18mm x 65mm