Agony of Confusion About Batteries and Current

LED Flashlights – General Info
1

SEEKING A COHERENT and CORRECT UNDERSTANDING of Li Ion BATTERIES for DECENT TO EXCELLENT FLASHLIGHTS

I am thinking a decent flashlight is one that is a lot brighter than your grandfather’s incandescent bulb flashlight, with LEDs instead of the filament bulbs, built tough enough to live through more than a few batttery replacement or recharge cycles. Key chain lights are not flashlights., so a small decent flashlight is going to take at least 1 RC123 or three AAA or AA cells, which is decently only if has good electronics and non-embarrasing host.

I am thinking an excellent flashlight is going to be in a rugged host and send 1000 lumens out the front.

There is a kind of good flashlight that produces less than 1000 lumens but can survive a nuclear war, like lights from Malikov or Sure Fire. I’d call those special purpose decent flashlights.

MY AGONY
My agony regarding chargers and data has been strictly on the discharge side. I understand that rapid charging of high drain Li ion cells doesn’t save much time because any gain on the rapid charge up to around 4.0-4.1 volts mostly is paid back when the current drops for the rest of the charge cycle, which will run longer after a rapid charge for the first part of the cycle. And for the little time saved, the cells pay a with a more rapid degradation than charging with lower current to begin with.

It’s the discharge that I have found kinda hard to get a handle. I want to make discharge charts like the ones I see in reviews, but I don’t know how to do that. I heard those charts come off custom rigs. I am picturing a custom discharge setup for testing cells and/or a flashlight . When it comes to the actual discharge charts, it looks like there is commercial software for making the charts. Does that mean the custom test rig has to be connected to the computer, and that is possibly accomplished through a USB connection?

I am picturing vendor of battery test systems saying, “This diagram shows how your usb ports/pins have to be setup on your electronics bench for a billion things our software will do, you have to figure . BAscially, you are going to need a circuit ut how to translate that into what you want to see for flashlight batteries that for battery discharge charts, that means you need a circuit with three connection points, plus ground. The connections would be

  1. Battery positive
  2. Battery negative
  3. between the battery positive and the positive side of your charger (or between battery negative and whatever the charger has connected to the battery negative.

Those inputs are going to go through a circuit that is connected to the pins of a female usb micro or usb C . Then a a usb cable goes from the usb micro or C to USB A on a computer, from there to the graphic software that graphs a billion things, battery charge cycles being on possible use of more than I ever would think of.

I don’t see anything like that offered for sale. I figure that must mean I am badly confused.

QUESTIONS TO RELIEVE MY AGONY

Regarding the crazy high current in RC and drones which can be more than 1000Amps, on a burst, I thought the best RC cells today are LiPo. Is it the LiPos that run up to 1000Amps?

Regarding flashlight current, when I see 8A draw mentioned in connection with a flashlights, is that going to be at least 4 cells in parallel to get that current? Or maybe 2S2P bucked down to 3 volts with high current? Was that one of the stupidest questions in history, because it makes no sense?

On the BLF Q8, how can you measure the current?

2

I am having a hard time keeping up with what you are trying to do but, I would suggest rudimentary reading on basic Ohms law and DC circuits in general. If you go trying to hook up a high drain cell to one of your computer USB ports, you are going to have serious problems. They make computer controlled chargers that do what I think you are looking to do. So the charger/dishcharger does all the work and just sends the data to your software program via USB port. No current from the battery is going to be flowing into or out of your computer. If you just want to take a measure of current draw a flashlight has on a cell then that said current will have to actually flow through the testing device you are using to get your current draw. A clamp meter is a good way to do it. You can also measure current with most basic DMM’s but you are going to lose accurate measurements because of the extra resistance added by the DMM itself and the probes used by the DMM. Most hobby type or cheaper DMM’s will only measure to about 10amps or so give or take. Depending on what you want to spend on a meter.

Do yourself a favor and become more knowledgeable of basic electricity. If you have the basics and know the fundamentals you can keep yourself out of a bunch of trouble.

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Or get yourself way way deeper into it. :laughing:

4

RC lithium packs are mostly LiPO (sometimes LiFePO).
The lipos like this one can do 150C * 6A = 900 amps of burst current

They can also be charged at much higher currents than flashlight batteries

Cylindrical cells used in flashlights are Li-ion not Li-PO, and are rated for much lower discharge rates (typically 5 or 10C max)
The Li-ion technology is usually NCA or NCR which gives much higher Wh/kg and Wh/L than LiPO, but there are several other ones too.

8A draw from a li-ion cylindrical battery is not too much, most cells can handle it fine so no need for multiple cells in parallel.
Of course you won’t get very much runtime by drawing 8A from a single 3000mAh cell, less than half an hour.

5

This is exactly the type of scenario that is giving me agony.

I can see on flashlight batteries where they are rated for current from 15A-35A on some common batteries.

Now when let’s say one cell like that is going to run a Convoy S2+ with an LED made for running at around 3-4 volts, it seems to me the numbers I find associated with that are like 2-5 amps, nothing like 15-35 amps.

Then consider an Evisar D4, that has four leds in it. In that case, there is going to be one cell driving 4 leds, that each could have 2-5 amps, for a total of 8-20 amps. Now I can see how that flashlight is going to pull current like what cells are rated to handle

I think I can figure out how to use my DMM with some heavy gauge wire to get an approximate measure of current by removing the tail cap and putting the heavy wire leads between the negative battery terminal and the body of the flashlight, but I am not seeing a good way to do something similar with a BLF Q8.

The only thing I knew for sure is I would humiliate myself by attempting to ask questions on this topic. Since that prediction is proving true, I am happy to be right about one thing.

I am so embarrassed that you have proven that I suggested one of the worst possible ideas unless my goal is to destroy my computer. I did not mean to suggest hooking up a high drain cell to a computer USB port.

Another dumb thing is I didn’t know about the computer controlled chargers that send data to printers. I did not say this, but the reason I am asking any of these questions is I have not been able to identify a charger that has the ability to send data to a printer.

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I think the following articles by HKJ would be useful to you:

If you have questions, ask. Somebody will know the answer. There is no reason to be embarrassed.

Edit: The following is Mooch's testing station. Mooch is a highly respected battery reviewer in the vaping community (which also uses 18650s), just like HKJ is to the flashlight community.

New Testing Station (on youtube)

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@danallen, you do not have to be embarrassed at all.

Asking questions is always good.

What do you actually want though?

Do you want something that can test various types of batteries, while outputting data to a computer?

Do you want a charger that can do this?

8

This only applies if the flashlight is running in direct drive.
Usually flashlights have a driver which regulates the current, so instead of 1 LED getting 5 amps it would be 4 LEDs getting 5 amps, which is 1.25A per LED.
This leads to higher efficiency, aka longer runtime with less heat.

9

Well, yes, by running at low output.

To get full power to each led you need to run ~5 amp per, or 20 amps total.

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It is tricky to do good discharge curves. Firstly you need a way to record the data, that usual means a compute connection, but you also need some way to discharge with the desired current. For lower currents you can use a analyzing charger with computer connection, but for higher current you basically needs a real electronic load…
Next question is where do you measure the voltage? Directly on the battery terminal or somewhere after the connection. In usage the useful value is somewhere after the connection, but it can be discussed how good that connection is and if the test setup has the same quality as the usage scenery, this is very significant when measuring the voltage some distance from the battery. In my test I had a few mOhm, that is a few times 0.001ohm in the connection (I used cobber rods and measured the voltage on the rods)., this may sound low, but is a significant voltage when drawing 30A. Today I use four terminals rigs that has two separate connection to each battery pole, one for measuring voltage, one for drawing current. This means my result shows the values on the pole of the battery. This is better than any application will be able to do, but allows very precise comparisons.
If you want to calculate on the result you need to know connection resistance and circuit resistance.

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Wow. Now this answers just about every question I can think of. Exception: how did this guy get all that gear?! That is a big investment, I am in complete awe.

Thank you for directing me to this treasure.

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Thank you. I am starting to notice recurring concepts from thread and other conversations. Your note is good summary of all I have been able to pick up so far.

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what I hope to get from this thread information and insight on a at least a half dozen areas related to flashlights, batteries, led drivers, expected performance and testing.

Now what I want is a rig like the one connected to this link:

Lab Setup

First I needed to see something like that.

Basically I am trying to make cheese in my head more like cheddar than Swiss., i. e. , I am filling in a lot of holes had hoped would have been filled on their own by now

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transitioning into wrap up mode for this thread

Just a few really simple questions.

1. What is the effect of adding 7135 resistors to a driver. My impression is each resistor provide an additional step between off and brightest, because. according to my unreliable knowledge, the resistors a are in parallel with one another and there ends my theory.

2. If I say I have a “7amp flashlight” , what am I saying? I know what amps are, but is that statement usually going to reference a certain type of light, such as a single cell single led light? It seems as if there are specs besides the current that are assumed and I missed the memo covering them.

3. Given an S2+ host, what do I need to buy to make a light like the blf a6? How will that be different for making 7135x8 instead? Is there a way to put three leds into it instead of one?

4. How come starting a thread with exactly the same opening post on candle power forum instead of blf would have resulted in a a really negative response? Actually might be a false impression. I never tried starting a thread there, because I never have had any post there count toward the three needed to be allowed to start a thread, but the point remains, how come I cannot come up with a single comment that counts toward the three needed to? It is humiliating.

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The purpose is to limit the current and in the case of 7135 also to stabilize the current. Without you would get a brighter light, but probably not for long (The led would die due to over current).

Current is not saying everything, you need both voltage and current to get power. When talking about flashlight the voltage is often assumed to be the voltage drop for one led, at the specified current.
A freshly charged LiIon battery has more voltage than a led needs, a depleted battery less, this means a flashlight usual needs something to limit the current from the freshly charged battery, to avoid blowing the led (like 7135), but when the battery gets discharge the brightness will drop.

16

That is what I was looking for, thank you.

With regard to adding a 7135 I understand going from zero to 1 resistor. What is the point of adding 5 or 8 instead?

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7135 is not a resistor, it is a current regulator, each one will pass 350mA, using two means 700mA, using 3 means 1050mA, etc.
With resistors it is often a question about getting the correct values and power ratings, it is easier to parallel a couple of common values, than try to get a special value in a high enough power rating.

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Read Driver - Flashlight Wiki for the basics.

LEDs are most efficient at lower currents, so using only as few 7135s as needed is better.

FET+N drivers(often FET + 1 like in the BLF A6) have 2 separate channels that run at different rates using PWM. For currents below N * 350mA they will use only the 7135 and keep the FET channel at 0%. For higher currents they will use both, but then current is not longer regulated.

Search for FET and FET+1 in the search dialog.

A more complex driver often will have a better microcontroller (i.e an attiny25 or attiny85 instead of an attiny13) with higher storage capacity, so a more complex firmware will fit in it.

Also check out FW3A, a TLF/BLF EDC flashlight - SST-20 available, coupon codes public - #5622 by ToyKeeper

As how to make a triple led flashlight, I never done it, but i’m sure it’s well covered in previous threads.

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Oh!!! well that paints a different picture from the wrong one I had in my head. Thank you very much.

20

The information in this thread is immensely helpful. Now I am starting to feel like I am amongst the information needed to start having a clue what’s going on the number of people who have contributed directly to my questions is a lot, it is unbelievable the level of support. I am actually moved deeply.