Too high current for battery dangerous?

Batteries and Chargers Rechargeable Batteries
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Hi! So I finally joined BLF, feels great! :slight_smile: I have much to learn about batteries (and everything really), I have read a lot on the forum, but trying to clear some things up…

I’m really trying to be as safe as possible with this wonderful hobby, don’t want to endanger my fellow familymembers. I have a bunch of Sofirn lights with their included batteries, and things have worked great… I really like Sofirn! I wasn’t thinking much about this, until I bought SC33. A wonderful light, plenty bright, wonderful tint. Anyway, as bright this light was on turbo I was baffled to learn that the included battery only is rated for 10A. I didn’t find anywhere how much current this light draws on turbo, so I bought a protected cell rated 10A and tried it. It tripped on turbo, so it must draw more than what the included battery is rated for.

Started to look into how much the lights draw, and found that some lights draws much more than the included battery is rated for. Like the SC21 Pro, according to ZeroAir’s review it draws 5.42A on turbo, the included battery is rated for 1.6A max discharge rate.

  1. Isn’t this dangerous?
  2. I guess Sofirn’s batteries have CIDs, so they will just vent if something goes wrong?
  3. Can the battery actually draw too much current and damage itself, or does it simply stop at a current based on internal resistance and such, and doesn’t harm itself? If that is true with a FET-driver, how about the boost-driver in SC33?
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Its not dangerous. The battery will only put out as much as it can. What you are losing is lumens. You should try some performance high discharge unprotected batteries some time. You will never go back to protected.

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It is kind of dangerous. The battery will age faster and run hotter, both not particularly good things. It’s a good idea to always use cells which are rated for a higher discharge rate than the flashlight can use.

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  1. With a FET driver, the voltage sag of the cell at higher currents limits the current draw, so it’s kind of self regulating in that way. A boost driver will do the opposite and draw more current as the cell voltage sags, although the driver itself will have limitations in this regard.
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Thank you for your replies! Very interesting!

This battery I tried was freshly charged, so that would mean the current would be even higher as the battery voltage goes down. So if it draws let’s say 14A at 4.2V that would mean above 17A at 3.4V? It would be interesting to know where the limit of Sofirns driver in SC33 is. In a review on youtube there were no lumen-increase in this light with a HD cell compared to the included cell.

I think I will follow Valynor’s advice and get a better cell for this light. If only I knew how much it draws. If it had a removable tail cap I think I could measure it, but now it seems much harder to measure.

Unprotected batteries are as safe as protected batteries, even if the flashlight short circuit somehow? (Edit: Have to add, I never run batteries down and I charge them in my XTAR VC8)

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Protected cells are 1-2mm longer and might or might not fit into your flashlight and can also cause issues when the light draws a high amount of power. At least in theory a properly designed flashlight should never short out your cell (it’s way more likely that this happens when the cell is outside the flashlight).

One way to solve the problem which battery to buy is to just get one of the best ones on the market, they are not even particularly expensive. For high-discharge 21700s that would be one of these:

Molicel INR21700-P45B 4500mAh - 45A
Molicel INR21700-P42A 4200mAh - 45A
Samsung INR21700-40T (40T3) 4000mAh - 35A

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welcome to the forum NightWanderer :wink:
congrats on your new light
I respect your curiosity and desire to learn more

This is my Anti-Turbo Soapbox:

with all due respect, focusing on Turbo performance is a fools errand. Turbo is not a sustainable output, it is mainly a marketing metric.

Look at this chart showing how quickly Turbo drops:

here is the complete review

you are correct that using a protected battery is not a good idea, because it can trigger the protection circuit if you try to use Turbo, leaving you in sudden darkness.

I would disable the Turbo feature, which would let you use the protected battery, although, the light has built in LVP, there is no benefit to using a protected battery. The stock battery is fine.

Turbo is just a marketing feature, imo, it has little practical value, as it is not a sustainable output. It will just generate excess heat and drain the battery a bit faster. The output will step down regardless.

btw, dont fall into the Turbo trap of firing Turbo multiple times in a row. That is a recipe for overheating the light. Turbo is just a marketing feature…

I advocate focusing on Sustainable outputs, instead of Turbo.

I definitely do not recommend buying a higher Amperage battery, because that will sacrifice total capacity and runtime. Unless youre just one of those people that want to see how hot you can get your light, by using Turbo for brief moments of unsustainable output. :wink:

Turboitis is a pitfal from reading marketing material. Look at the runtime chart to develop more realistic output expectations.

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Educate yourself and get off the “protected cell” BS train. They’re a waste of money, and will rarely provide the juice necessary to provide full output in 95% of today’s advanced flashlight platforms. Not to mention the dimensional issues and self discharge inherent from the built in monitoring circuits. The only relevant metric is the discharge rate of the cell you install in the particular light you purchase. Yes, there are several nuances to consider in order to be confident the cells you choose are capable of supporting the hardware they are installed in, and likewise safely handle the extreme parameters. There’s a learning curve, and everyone goes through it.
Don’t be intimidated by the over exaggerated horror stories surrounding “unprotected” li-ion cells. Buy quality cells appropriate for your application from trusted sources, use common sense and safe handling practices, and you’ll never have a problem.

Pretty much any reputable 21700 cell sold today will easily handle the SC33. Sofirn package cells are fine.

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Thank you! It’s great to have found a place I can talk about these things without people look at me like I’m some kind of nutcase, haha.

You make a great point! When out in the dark, a sustained output for a long period of time is much more valuable than a short burst. I hate it when I have used turbo and then the light have to cool down and the output is so low I can hardly see anything for a while.

But with that said, when out in the dark and you hear a wild boar scream not far away, you want that turbo to see what’s happening. :smile: That’s why I usually carry more than one light when out.

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Thank you for your comment. Yeah, that’s what I’m trying to do. But I have to say, I would gladly pay double the price for the cell if it just meant another layer of protection for the battery.

But doesn’t always seem to be true. In a single cell light it seems it’s always the more safe option with a protected battery, but in multicells lights it might actually cause more problems. I guess it could have something to do with the cells interacting with eachother in a way the internal protection was not intended for?

As I’m trying to educate myself I’m now trying to understand how the same emitter can draw so different currents. Let’s take an example, SP36 BLF run the LH351D with 10mW/lumen, but the SP10V3 run it with 19mW/lumen. They are both using a FET driver. What am I missing here?

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in addition to the step down after turbo, there is also the fact that by using brighter light our eyes also downregulate our light sensitivity, so we cant see as well with dimmer light, that would have worked fine if we had not blinded ourselves by using turbo

I would gladly pay double the price for the cell if it just meant another layer of protection for the battery

faulty logic… LVP is intended to prevent the battery from getting overdischarged, too low voltage… does nothing useful until then

the real distinction between when to use a protected battery, is IF the light itself does not have built in protection, Then use a protected battery.

in the case of Anduril lights, the protection is built in to the UI… adding a protected battery does not “double the safety”.

when out in the dark and you hear a wild boar scream not far away, you want that turbo to see what’s happening.

A protected battery can put us in danger… for example, if the light shuts off completely, due to tripping the battery protection. Now we cant see the Boar at all…

imo using a protected battery with Turbo, is a bad idea. Much better to use an unprotected battery, so the light will still work after turbo (with lights that have built in LVP such as Anduril lights).

fwiw, here is a good info source about LiIon Safety

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A rule of thumb I’ve heard is 3 amps per 1000 lumens (assuming single cell). So if your light is 3000 lumens then that would be 9 amps, but I would probably get a 15 amp Samsung 30Q or similar over a 10 amp cell for the extra overhead and less voltage sag.

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Out of curiosity I pulled a couple of 3400mAh protected Panasonics off the shelf and checked the voltages. One of them was even installed in a shelf queen light. ~3.7 volts on both of them after sitting untouched on a shelf for at least 5 years. Any drain from the protection circuit is overstated it seems.

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Here is a comment from the link you provided: Protected batteries are generally safer than unprotected batteries. I’m trying to understand how you think this is a faulty logic. You know protected batteries protect from more than only LVP? If a flashlight doesn’t draw more than 8A on turbo, and the battery has a limit at 10A, if the light suddenly draws more on turbo there is something wrong with it and thus a second layer of protection has protected the battery.

Electronics can fail, there could be short circuits after you drop the flashlight in a flashlight with lower quality, it could leak in water, Anduril have many bugs in my lights, the list goes on…

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That’s a great tip, thank you!

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Protected batteries add several new modes of failure.
-they have an electronic board itself that can fail in various ways
-they run a thin metal strip alongside the battery to the + terminal for power - very easy to damage if you drop the battery and this might result in an immediate short

These kind of failures are not possible in unprotected cells.

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the faulty logic is the belief that using a Protected Battery in a light that has built in Protection somehow adds a second layer of protection

The protected battery actually adds a risk of sudden darkness, when the Protected Battery’s protection trips.

my main point is, IF the light has built in Protection, adding a protected battery creates a dangerous point of failure

Sudden Darkness can be a Very Bad thing.

If a flashlight doesn’t draw more than 8A on turbo, and the battery has a limit at 10A, if the light suddenly draws more on turbo there is something wrong with it and thus a second layer of protection has protected the battery.

I do not follow your logic that there is something wrong with the light, when it trips the protection of the battery. To me, the protected battery is the problem… Having a protected battery trip, is inconvenient, and potentially dangerous.

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Thank you for your replies! I will think more about this and read more about it. Your input has been valuable!

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Protected batteries have their place. Like I said , once you use moderate/high drain unprotected, you will never go back. It truly unleashes the power of your flashlight.

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