Using a battery with low discharge rate in a high discharge device

Batteries and Chargers Rechargeable Batteries
1

I have a Panasonic NCR18650B, which is rated as being 3400mAh 4.9A. What would happen if I put this into a 5A driven light? How about an 8A driven emitter? The lights I own are as follows, I don’t know what the draw on these units is or how to get this information:

  • Nitecore P10v2
  • Skilhunt H03C RC
  • Convoy S2+ with CSLNM1.23 5 group red 620nm emitter (2.5A ?)
  • Convoy S2+ with 519A 12 group (5A ?)
  • Convoy C8+ with CSLNM1.TG (6500K) 12 group (5A ?)

I plan to use the Panasonic NCR18650GA (3450mAh 10A) battery with these units. So, I’m just wondering out loud. :slight_smile:

2

Very simple. You would throttle the light output. Meaning you would only get as much light as the current you are putting in.

The GA’s are among the best batteries, but they are not high performance batteries. They are meant for long life.

3

Thanks for joining the gang, pcunite!

4

Well, these cells that can’t deliver quite as much current will still work, they just work harder and generate heat. They generally have more (or a lot more) internal resistance just as a function of their magic sauce inside. The higher amp cells have much less resistance and they change the sauce a little too. This is why the higher capacity cells always have lower current delivery and vice versa.

If you can, it’s best (for long term retention of capacity and overall cycle count/life) to keep your current draw around 80% of the tested comfortable max current delivery of the cell. Rated/labeled vs. tested are often not the same numbers. In HKJ’s tests he didn’t take that Panny cell past 5A back then (long time ago) but you could tell via the temp and voltage drop that they were getting close to their practical comfort level. Running the 18650B at 5A will work fine but it’ll be warm and due to the added strain you’ll see more voltage drop - will likely see light output dropping quickly as well as shorter turbo time or not being able to get into turbo as the cell depletes. For brief bursts, it would be fine, as heat buildup and voltage rebound between uses will give some recovery. Using something like a 15A cell that can comfortably run 5A will just be smoother, so to speak, less heat, less strain, able to maintain voltage much better without sagging so much under load. Running that 18650B cell at 8A…pick another cell.

As long as the cells are healthy, over-amping them within reason shouldn’t be terribly dangerous to you or the light, but the extra heat might eventually cause the built-in safety valve in the cell to blow out, killing the cell (that’s not aftermarket added protection, just the original design failsafe that all manufacturers incorporate). That heat would be intense no matter how much metal the host had to help dissipate it…just too much for the jellyroll in the cell to cope with. Also, protection circuits and added buttontop plates can increase resistance a tad.

If you search for reviews (here, Zeroair, reddit, CPF, etc) better reviewers will take electrical readings and share them. That’s usually done on the battery side of the driver so it’s not what the emitter actually receives, but it’s close enough to be helpful. For older linear drivers that just use the 350mA 7135 chips for regulation, you can just count the chips and add that up, figure a +/- 15% reduction for heat/inefficiency/resistance in the circuit and have a pretty close estimate. Lights controlled by FET chips, boost/buck circuits, etc…need to measure with a meter unless you’re an electronics whiz.

The 18650GA is ok, should handle all that fine, but there are certainly lots of better choices these days, and for pretty cheap. Over the years the magic sauce in the jellyroll improved a lot, so now we can enjoy higher capacity cells with higher current delivery at the same time. If memory serves, the GA is more like a 7-8 amp cell, about on par or a little less (more sag) than the Samsung 35E.

5

Here’s HKJ’s battery comparator tool……it’s wonderful. He’s got a couple others but this is the one for 18650 cells (has 21700 grouped in there, too). There are two drop down boxes with a long list of different cells…pick one and the graph will show some test lines. There are checkboxes above the graph where you can turn on or off various levels of current. He hasn’t tested every cell and in recent years he’s tapered off a little bit, but it’s a very handy way to a) compare cells, and b) see actual test measurements for voltage and capacity. Also, when you select your cell(s) a link will appear by the dropdown box that you can click if you want to read his full test review for that cell (lots more information). Mooch from the e-cig forums also does great tests and sometimes he’s covered cells that HKJ hasn’t….can google that name + battery tests and find the links.

https://lygte-info.dk/review/batteries2012/Common18650comparator.php

6

Excellent, thank you.

7

You’re welcome, and welcome to the forum!

8

My vote is dont worry about High Drain, just use the battery you have.

Try this on, I will play Devils advocate :smiling_imp:

We dont need no stinkin’ High Drain Cells… :confounded:

fwiw, I just tested a FWAA with a 10A cell and got 1100 lumens, and a 3A cell that maxed out at 900 lumens.

Neither of those maximum output last more than a second, and after 40 seconds both batteries were running at 200 lumens, due to thermal step down

so imo, it makes no difference whether you use high drain or not, because high drain is only for a few brief seconds

imo it makes a lot more sense to just run the light at a sustainable level, which is about 300 lumens for a cold FWAA running 14500, and both batteries can support that output, no problem.

similarly with all the lights you listed, if you run them on 18650 you can hope for about 500 lumens, sustainable… and you dont need High Drain for that. And no, low drain cells dont run hotter, they just run dimmer Max… but if you run at sustainable output, by definition the light does not overheat, and the lower drain cell usually has more capacity, longer runtime, more practical.

I rest my case :student:

You be the judge… LOL

If the light Works, Use it.

9

I understand the sentiment and there is truth to your statements balanced out with what others are saying. I’m new to led emitters and learning a lot quick.

A long time ago I was using AA rechargeable batteries in some flash units (photography) that I had at the time. I learned the difference between Sanyo Eneloops low self-discharge vs Maha PowerEX high drain and speedlight flash recycle times. Things have improved I’m sure, but back then I could charge the PowerEX the day before an event and they would just power through a flash session. Really amazing. But they wouldn’t hold a charge for a week! It was give and take, so I had both style of batteries. Maybe things have improved now to where you get both behaviors.

Since I’m new to this world, I’m noticing with flashlights that, as you’ve noted, “turbo” is really a special trick. How much draw vs runtime, vs output … its all a tradeoff.

10

true, and welcome to the fray

runtime graphs really tell the story, I like the ones zeroair posts in his reviews
googling “fwaa zeroair”
finds this runtime chart:

it illustrates the drop in output by about 50% in the first 4 minutes, and a sustainable output of about 600 lumens…
here is the review

11

There are eight zillion lights to pick from these days and output/runtime/”performance” really just depends on that particular light (the emitters, how many of them, but most especially the driver controlling the fuel). You can get performance like Jon mentioned with his FWAA or you can get different performance with the same light as shown in Zeroair’s graph here (these differences can be attributed to battery choice and how you have the Anduril firmware configured in the driver…tons of options with that complex and wonderful firmware). And there are lights with fancier drivers that can indeed drive the emitters at higher amps for longer periods of time. Those with boost or buck/boost drivers will attempt to maintain a steady output and some of those are made to be pretty powerful (although heat does come in to play whether or not a light has some sort of temperature management in it). And lights like the Convoy M3C can sustain over 1000 lumens for literally hours and it doesn’t get very warm at all (it’s somewhat of a standout amongst today’s lights…most will behave just as Jon said and the graph shows, where “turbo” is an extra boost above “high” mode and is really intended just for brief bursts of extra light…not to be considered a sustainable mode at all, but of course that’s how many lights are marketed with the numbers…).

Good to learn about cells and such. It doesn’t always matter but sometimes it does, so good to know and be aware of. If you always only run your lights at low levels then no, pretty much doesn’t matter.

12

or 1500 lumens for 1 1/2 hours… per this review

considerably more than the Aluminium FWAA that zeroair posted

the differences include weight and battery size
the M3C weights 13 oz (more thermal mass, more heat dissipation), and fits a 5500mAh battery

while the FWAA weighs 2 ounces and has a 1100mAh battery

so the M3C is 6 times heavier, 3 times brighter, and the battery has 5 times more capacity…

now back to our regularly scheduled list of 18650 lights that the OP posted…

the Devil is in the Details… :smiling_imp: lol :beer:

13

Jon, you cherry picked the comment but your example doesn’t contradict what I said. If chart comprehension is a challenge, the text of that review actually says that they got 2 hours 20 minutes of constant 1500+ lumen output with a 5000mAh cell…so what’s your point here? I mean…it’s plural…and sustained…so. My point was helping OP, new to the hobby, hopefully understand a little more of the nuances between cells and drivers and that was one example (of out eight zillion, according to me…).

(btw, I do get over three hours of run time on my M3C but I’m using the 26800, not quite getting 1500 lumens either but close enough for a comparison)

14

Good. I was trying not to be contradictory. :innocent:
Using alternative facts… :smiling_imp:
How did I do? :partying_face:

and youre right, 1500 lumens for 1 1/2 hours

I was adding to your comment, to point out mass and battery size affect runtime and sustainable ouput levels.

I also agree that lower output runs proportionately longer… as in your 3 hour 1000… Im a fan of less is more… LOL

keep up the good work… Trust, but Verify :beer:

I hope the OP got the info he was looking for… :wink:

15

Understood gentlemen. The large amount of details make it interesting.

16

thanks for the chance to have an interesting discussion, Im glad you asked the question

fwiw
The battery cannot overheat by being connected to a driver that could use a higher Drain rate battery.

the driver does not Pull power out of the battery
the battery Pushes power into the driver

illustration

think of the driver as a water pipe
think of the battery as the water pressure
when the light is turned on, that is like opening the faucet.

How fast the water comes out (Drain rate) is based on the water pressure (Battery),

The drain rate is not based on the size of the pipe (Driver)

17

Great work, folks. I learned some stuff too. :+1:

18

If the battery doesn’t overheat from drawing too much current then wouldn’t short circuiting it be harmless? Aren’t high current drivers the equivalent of a partial short circuit to a low current battery?

19

that is not logical, because

No one has proven that the battery Does overheat.

The burden of proof is always on the person making an assertion or proposition. Shifting the burden of proof, a special case of argumentum ad ignorantium, is the fallacy of putting the burden of proof on the person who denies or questions the assertion being made. The source of the fallacy is the assumption that something is true unless proven otherwise.

One cannot logically claim that “miracles exist unless someone proves that they do not exist.”

One cannot logically claim that “batteries overheat from high output drivers unless someone proves that they do not overheat”

20

There are whitepapers from all the majors that have been available for many years….spells everything out pretty clearly. 80C is a smart cutoff, which is easy to exceed if you design something that really puts the beans on a cell that is not up to the task. I think it’s around 140C or 150C where thermal runaway becomes a real possibility, but we’re generally never going to see that in a flashlight unless there’s a sustained short circuit on the cell itself…other shorts, hopefully some other component fails and opens before things get out of hand.

If cell manufacturers aren’t to be trusted or it’s hard to find those whitepapers of yore, here are some more recent treatises (ones that are not overtly focused on thermal runaway, because in precursory searches that’s what comes up the most due to a flurry of research and tests after many of the consumer product fiascos over the last several years in devices that were poorly designed and/or modified/abused).

Overheating Prediction and Management of Lithium-Ion Batteries - 2018 - exhaustive work by doctoral mech engineer

Science Direct host article: Temperature effect and thermal impact in lithium-ion batteries: A review - Dec 2018

Jon, not sure why you’re in the mood and yanking chains but sheesh. All of this is old hat…one would assume that you have this knowledge already…or I would, from your comments and statements over the years here. Between old threads on this forum (search!) and other easily found resources that are easier to digest than the techy research and reports, there’s no need to reinvent the wheel for any reason. The chemistries and other niggling factors have changed a little but physics has not.