Current Limiters On Protected Batteries

[mcquinn]

I was researching protected batteries and found out something interestingto me.The protection board not only cuts them off if they over charge or if the voltage drops too low but they also limit the amount of current flow to 0.5 amps.What this means is a 5 volt mod with protected batteries is going to be quite a bit cooler than a straight passthrough at 5 volts.For those of you building mods I would look into hooking your batteries in parallel fashion as two hooked up that way will give you 1.0 amps of current.When you run two batteries in series like the crc123's you are running through two of theses circut boards and I have no idea what happens then but I am sure you would not get what you think you are getting.The voltage which is easy to measure would be what you expect but the current flow is going to be at the most 0.5 amps maybe less.I am not posting this to insult anyones equipment as I think it is all good this is just a FYI about batteries.Some of you might already know this but it is new to me.

[Brandon]

For some reason, datasheets on batteries are getting harder and harder to come by. And it really shouldn't be this way.

But after some digging I found a post on DX in which someone had tested the famous TrustFire 14500 protected batteries at a 700mah (0.7amp) discharge rate, and not only did they perform at that discharge rate but they also had a relatively stable voltage depression throughout the test. I say relatively stable b/c looking at the graph you can tell it's not fantastic, but considering how cheap they are I find it very good. Here's the post: http://www.dealextreme.com/forums/Forums.dx/Forum.19626~threadid.523314

Mcquinn can you get more specific about the batteries in question that you mentioned? Because with the 14500s, they really can discharge higher than half an amp.

From personal experience the 14500s perform great under a good load. The double derringer mod I made still works great. Vapor production off just one atty (while the other one is firing at the same time) seems about the same as if I were powering only one atty off a 14500 instead of 2 simultaneously.

If I hadn't blown my multimeter's amp reading path a few months ago (everything else still works) I could test it for a concrete number. I definitely need to borrow someone's.

In the mean time I'll look around some more for a datasheet, but I'll be darned if they're burried somewhere in the depths of the internet.

[Tektronik]

Nerd Alert! Nerd Alert! Nerd Alert! All battery nerds please report to this thread immediately!

It would be nice if somebody with a VP-PT and 510 atty could get some good readings off it (volts and amps, we already know the resistance of a 510 atty) so we could use it as a baseline for comparisons to high volt portables. It's the only constant we have in this world of seemingly infinite variables. Oh, the chaos! AAAARRRGH! We need references, man!

OCD: "every thing has its place, and every place has a "thing""

[mcquinn]

You would have to build some kind of adapter to get a current reading as the meter has to be in series with the atty.I was looking at 10440's and 18650's and as I said they all either said half an amp or .2C which I am told is some kind of electrical engineering way of saying capacity of the battery divided by 4 And it seems to come out .5 ampsI was able to find specs on most common batteries at Battery Junction. .I am no electrical engineer by a long shot and full voltage at half an amp for a longer time than a stock battery is worth something.I was just under the impression that I was getting more than I turned out to be getting from single battery mods.

Edited March 27, 2010 by mcquinn

[mcquinn]

Here is what I find for specs on 14500 Trustfires

Product Specifications:

•Capacity: Nominal 800 mAh

•Dimensions: Diameter 14 Height 49

•Weight (Typical) Approx. 21 g

•Nominal Working Voltage: Average 3.6V

•Peak Voltage: 4.2V

•Discharge Cut-off Voltage: 2.75V

•Internal Resistance: <80 mOhm

•Cycle Performance: 85% of initial capacity at 300 cycles

•Cycle life: > 300 cycles

•Max. Charging current: 1C ma

•Max. Discharging current 2.5C ma (for continuous discharge)

again instead of telling us the discharge current they give you 2.5C and I am not sure what formula that translates into.

[Brandon]

Excellent specs there McQuinn, thanks for finding that!

The "C" rating is actually an expression of the cell's (battery's) rating of capcity. 1C = 1 times the rated capcity of the cell. So 5C equals 5 times the cell's rated capacity; 2C equals 2 times the cell's rated capacity, etc etc.

So if a cell's maximum charging current is listed as 1C as in the case of the trustfire 14500, and the rated capacity of this cell is 900mah (which is actually very optimistic and more along the lines of 700mah; but that's a moot point) then that means the max charging current is 1 times the rated capacity which is 900mah.

As in the case of the specs you found and listed, the max continuous discharge rating is 2.5C, which would equal 2.5 times the cell's rated capacity. So that's 2.5 times 900mah = 2250mah or 2.25amp hours. That's more than what we need for vaping since a normal 510 atty at 4.2volts (the maximum non-load voltage of our lithium ion batteries on a normal charger) will draw between 1.68amps to 1.9amps a maximum power and under ideal conditions.

Thanks for finding these specs, it's appreciated! And is another confirmation that we're running our 14500 batteries within specification for normal and safe operating conditions.

In the rechargeable battery world, a discharge rating of 2.5C is actually very low. Look at some of the LiPo (lithium polymer) batteries used in RC hobby planes and land vehicles (different chemistry yes; but also a good side comparison). The normal discharge rating for LiPos for these applications are anywhere from 20C to 50C. And when you venture into the world of LiFePo4 nano-phosphate batteries, the max discharge rate can exceed 50C.

This is hard to imagine just looking at numbers, so here's a real-world example of how powerful the newest (and most expensive) battery chemistries can get. Start your car on a 4 cell pack of small little batteries?! Yup, and here it is in canada at -21celcius (or 5.8 below zero fahrenheit): http://www.youtube.com/watch?v=qcvmvrmTMMk

Keep in mind that your car's lead-acid battery is actually 6 cells in series in one big housing as opposed to only 4 cells in the above example. Much smaller and soooooo much lighter.

I saw another video of a 4 cell pack of the same batteries jumpstarting an old V8 chevy around 8 to 10 times in a row in rapid succession, but I can't find it now.

Any way, even though Lithium Ion batteries are good and more than serve our needs in the vaping world, they're really just a drop in the bucket compared to what battery chemistries are capable of.

Dang I love batteries.....

[wagex]

it really depends on the brand of battery and the size of the battery and the type of battery it is depending on what the protection circuitry cuts out at. but it is a good question also some people get the cut out midex up with the way they tested the mah rating such as 1 amp for 1 hour or .5 amps for an hour to get the MAH rating.

[ddavelarsen]

...

OCD: "every thing has its place, and every place has a "thing""

Well this is totally off topic (and a very interesting topic indeed gents, thanks!) but OMG -- That is me to a freakin T! Cripes man, that just blew my mind.

[mcquinn]

I aparently don't understand what I read and so I posted in error about the 0.5 amp ,I apologise if I caused anyone anxiety.There is no easy way for someone who is not an engineer or at least good at algebra to know what the specs for lithium ion batteries mean.What I was able to determine was all of them are usable ,the bigger the battery the longer it will last .I guess that should be good enough.

[Brandon]

I doubt you misunderstood McQuinn, it's just that there are so many different battery sizes, styles, brands, and chemistries.

It's hard to keep them all straight, but I do enjoy learning about them.

[Tektronik]

Brandon,

I've been talking to this guy who owns a battery shop. He sells the tenergy brand of cells in all sorts of sizes. I got him to order me some 14500s and keep them in stock. He called me today to tell me that they arrived. When I arrived, they were 14500s, but the unprotected version. I don't think tenergy has a PCB version of this particular model. I bought two and charged one of them this evening. When I got a green light I tried it out. The magnum atty I've been using gets hot very quick, I mean hotter than what I'm used to with the protected trustfires, and that's even using a stainless T-tip. On a magnum atty with the trustfires and T-tip the atty never got this hot: the t-tip would dissipate well. With the unprotected tenergy, I can't tell if the battery itself is getting hot because the heat from the atty dissipates down the casing of the VP2 and warms about half of the battery casing. The battery is not hot (not like HOT) just a little warmer. Can you please try and research the "C" - max discharge current- of this unprotected battery- think that maybe the battery may be putting out more current than the protected trustfire version. I also notice that when starting off with a cold magnum, RY4 juice looses its taste on a tenergy when compared the same way with a trustfire. Higher current? That's what I'm eluding to.

[Tektronik]

Tenergy website says 2.5C. Is that where mcquinn got his specs in his post? I wonder if the protected Trustfires have the same C rating as the tenergys.

[Tektronik]

I went ahead and looked it up. Here's what I've been able to find:

Trustfire 14500 protected: 1.5C max discharge current

Tenergy 14500 unprotected: 2.5C Max discharge current

Hmmmmm.....

[Tektronik]

I went ahead and looked it up. Here's what I've been able to find:

Trustfire 14500 protected: 1.5C max discharge current

Tenergy 14500 unprotected: 2.5C Max discharge current

Hmmmmm.....

Please confirm, thanks

Tek

[Brandon]

Gosh, these numbers are just all over the place!

After an extensive search today I STILL couldn't find a manufacturer's datasheet on the Trustfires. What the heck is up with that?!

From the very few sites I found that actually listed *some* tech specs, the consensus for the protected Trustfires max discharge rate is 1.5C. Which would be 1350mah (1.35amps).

I've just got to wonder though... Is this an RMS value or a peak surge value? Because there's a big difference. If it's an RMS value, then that would mean 1.5C discharge rate could be sustained for a very long time without damage, excessive heat, or cause for concern.

When manufacturers specify an RMS (continuous) value, they don't actually specify a time frame (like constant 1hr, 2hrs, 1 day etc etc) so you have to assume it's indefinite or just in other words a very long time.

When manufacturers specify a peak surge value, they nearly always specify an exact time frame (1sec, 1min, 10mins etc etc). So I still feel as though we're left with a question here. And I'm not comfortable saying that it's rated at a 1.5C total maximum discharge value.

Here's an example from Tenergy's website (different battery, since they don't have this specific of information on their 14500s)

Max. Charge Current 2C

Max. Continuous discharge 10C

Max. pulse discharge (10s) 30C

I really need to get another multimeter, because this issue is totally working on my nerves. I just have to test their discharge currents on some 510s!

[Tektronik]

You know, while my friend was here this weekend, we ran the numbers based off what we thougt was the trustfire C earlier in this post. We determined that at 2.5C, the 14500 was just under what was required for the current draw on a magnum atty. Something like the max current for the trustfire 14500 was close to 2.25 amps and the magnum atty wants 2.5 amps, or close to it. So the battery should get a little hot for it being underpowered, or drain faster than it's rated because of the slightly higher demand of a magnum. But when I found that spec that it was the unprotected tenergy 14500 that was rated at 2.5C and the protected trustfire is rated at only 1.5C then I figured I wasn't getting what I though I was getting out of the trustfire and the magnum. it was only when I put in that tenergy did i notice the physical difference with the heat and all.

[mcquinn]

Kind of what started this whole thread I am pretty sure for the most part we are not getting what we think we are but it seems to be more than enough to get the job done as we only use them for short bursts of energy.It would appear that you guys are Hot Rodders trying to tune the maximum out of your gear ,which is cool .keep it up although most of it goes over my head once in a while I understand some of it.