18650 voltage

Hi to all.
I am a complete newb when it comes to flashlights and batteries, so I have a newb question. I have a Nitecore p12 flashlight, powered by Nitecore NL183 18650 2300 mAh battery. The flashlight has a voltage indicator, which flashes every 2 seconds when the power is about 50%, and blinks rapidly when the power is low. It can also show the voltage accurate to 0.1 volts. I have read somewhere that an 18650 batteries should be recharged when they drop to 3.6V. My battery currently reads out 3.6V, and the indicator on the flashlight is blinking every two seconds, meaning it is on about 50% power.
I'm a bit confused. Should I recharge now, or wait until the indicator shows that the power is low?
Also, as the voltage drops, does the battery "life" drop, or the power of the output (lumens), or both?

I also have an Olight s15 running on a Trustfire 14500 battery. The flashlight does not have a voltage indicator, so I recharge the batteries when the light emmission stops. Is this wrong? Is there a difference how 18650s and 14500s should be treated?

Thanks.

Hi there,a 3.7v cell is around 40% charged at 3.7v,fully charged at 4.2v(100%)

So nothing to worry,yes can be a little confusing,have a read up on here via search for further details.

Not letting cells drop too low is good practice,so when showing 3.7v top them back off,this also increases life of the cells rather than deep charging from 3.0v for example.

Reg the s15,trustfire are not the best cells for consistency,some are ok,others not so,either way know when your light will stop.Learn to top off cell before this happens

Example..........2hrs use the light wont work,the voltage maybe 3.0v=not good for cell long term
So after 1.5hrs charge cell.

If not sure and used irregular then get into a habit of topping cell off after use.

Buying a multimeter is cheap(under $10) and can keep an eye on the cells pre and post charge will also help you identify any issues too........

Most Li-Ion cells can be safely discharged to about 3.1 volts under load, some are rated to go even lower. At 3.6volts, your battery still has about 30% of capacity remaining. Li-ion cells have no memory effect and never did, so they can be safely recharged regardless of current charge state, They tend to last a little longer if you don't run them down completely between charges, but even then you can expect several hundred cycles for battery life.

The design of the driver will determine whether or not the lumen output from the LED drops as the voltage drops. Most drivers will provide rated output as long as the battery can supply sufficient power to do so. Many are designed to shut down when the battery voltage reaches a certain point (essentially fully discharged). Check the owners manual that came with the flashlight to see how you light handles low battery voltage warning.

If you are unsure, or the flashlight lacks low voltage protection, you are probably better off using 'protected' cells. These are cells that have a small printed circuit board in them that sense the voltage and current, and will effectively disconnect the battery to prevent over discharge, over charge, or excessive current draw.

As others will tell, the quality of trustfire batteries is suspect. You should be using batteries that have a recognized brandname cells inside such as Panasonic, Sony etc.

Reg 18650 and 14500,both are 3.7v li ion cells,both 4.2v at 100% charge,treat same the 18650 has more mass,more stored energy over the 14500,but the chemistry is the same(li ion)

Have a read here
http://batteryuniversity.com/

educate yourself on the cells:twothumbs

Most of the Re-branded (Keepower, Callie's Kustom, Orbtronic, etc) Panasonic NCR18650 A's, and B's, have protection circuits that are good for about 2.5v's.

But I agree that one should not go to low, and recharge sooner for better, safer battery usage and longevity. Be sure to charge with a good quality Li-Ion charger.

jazavac said:

I also have an Olight s15 running on a Trustfire 14500 battery.

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If you care about safety, stop using that battery NOW, and replace with a reliable brand asap (which? check reviews on this forum for example). Or just use with NiMH's. Li-ions offer a higher max output in this light, but capacity-wise there isn't much advantage (if any!) in using a 14500 Li-ion. Besides that xxxFire batteries are often poor performers.

The flashlight does not have a voltage indicator, so I recharge the batteries when the light emmission stops. Is this wrong?

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There's a good way to check State-of-Charge with (regulated) lights that don't have voltage indication: check the higher-output modes. With a fresh battery, higher-output modes will work as intended. When the battery empties, for example low and medium modes will work normal, but high mode might be same as medium or not work at all. When the battery approaches near-empty, even a medium mode may not work as normal. So a quick step through the higher output modes will usually give a good indication of the battery's condition.

When you run a battery empty on high, that's usually okay. The output will drop before the battery goes "into the red". When you run it down in a medium mode, that might also be the case. When you run the light in moonlight mode until output stops, then the battery will be truly "dead" by that time. Which might be unhealthy for many Li-ion batteries.

In any case: when (rechargeable) battery is found to be "empty" (below 3.0V or so), recharge as soon as possible. For Li-ions 100% charge isn't optimal condition to be kept in (in contrast with NiMH's), but sitting empty isn't healthy for either type of battery.

Thank you all for you responses, things are much clearer to me now.

ven:
If not sure and used irregular then get into a habit of topping cell off after use.

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Can you please explain what "topping" means?

I have read, and am currently reading, about cells on http://batteryuniversity.com/, but as a complete newb to the world of flashlights and batteries, or electronics in general, there is a lot to learn, and things get confusing really quickly. So I am very gratefull for this forum and all the members for the possibility to ask direct and specific questions and get direct and specific answers, it saves me a lot of time and energy. Plus, here I can test if what i have learned on my own is correct.

RetroTechie:
If you care about safety, stop using that battery NOW, and replace with a reliable brand asap (which? check reviews on this forum for example). Or just use with NiMH's. Li-ions offer a higher max output in this light, but capacity-wise there isn't much advantage (if any!) in using a 14500 Li-ion. Besides that xxxFire batteries are often poor performers.

Click to expand...

I do have NiMH batteries, but the problem (for me) with them is that the lumen output on max setting, with a single battery (with two NiMH-s it works great), falls constantly. With 14500 I can get constant lumen output until the light shuts off, which is important to me in a lot of situations.
I guess the shut off with 14500-s happens when the voltage drops and batteries / flashlight protection kicks in?
So far I am quite pleased with Trustfire performance when compared to NiMH-s, but then again, I never had any better brand batterise, so I'll definitely have to try them.

And another question, just to see if I get things correctly: voltage is the power that a battery outputs, and mAh is the speed at which the power diminishes?

Thank you all again for your help!

Basically when i have used a light,few short uses, i top the cell off on charger,so charge for example from 70%/80% back up to 100%(4.2v)Instead of letting it go down to 3.0v and doing a long charge cycle

jazavac said:

I do have NiMH batteries, but the problem (for me) with them is that the lumen output on max setting, with a single battery (with two NiMH-s it works great), falls constantly. With 14500 I can get constant lumen output until the light shuts off, which is important to me in a lot of situations.

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Understood. Indeed 2x NiMH's work well, but I don't like the look/shape of the S15 in that config...
I use mine (Ti version) mostly in the low mode, which works fine with a single NiMH. And in that config, high mode works good enough for me.

And another question, just to see if I get things correctly: voltage is the power that a battery outputs, and mAh is the speed at which the power diminishes?

Click to expand...

Voltage (V) multiplied with current (A or mA's) = power (Watt). Power is an energy-per-time unit (ongoing, if you will). Multiply with time and you get a measure of total energy (Wh or kWh, when talking about batteries also known as capacity). Since for batteries the voltage is a relative constant (nominal voltage), often the current multiplied with time (mAh or Ah) is used as a figure for capacity.

For example a 12V, 50 Ah car battery might supply 12, 1A (= 12 W) for 50 hours. Or 12V, 20A (= 240W) for 2.5 hours. Or anything in between. Either way, total energy contents = 12V x 50A x 1 hour = 600 Wh (0.6 kWh).

So note that the same mAh capacity figure can mean different energy contents, if the nominal voltage is different! This is why a 1.2V / 2000 mA NiMH (= 2.4 Wh) and a 3.6V / 700 mAh Li-ion (= 2.5 Wh) have roughly the same energy contents.

ven:
Basically when i have used a light,few short uses, i top the cell off on charger,so charge for example from 70%/80% back up to 100%(4.2v)Instead of letting it go down to 3.0v and doing a long charge cycle

Click to expand...

Thanks Ven, I will make topping my common practice from now on.

RetroTechie:
Understood. Indeed 2x NiMH's work well, but I don't like the look/shape of the S15 in that config...
I use mine (Ti version) mostly in the low mode, which works fine with a single NiMH. And in that config, high mode works good enough for me.

Click to expand...

Yeah, I dont like it in 2xAA config neither. Much more practical as a single A. I use it a lot as a head lamp mounted on my hat and as a bicycle light, so for that use 2xAA is not really an option.

Voltage (V) multiplied with current (A or mA's) = power (Watt). Power is an energy-per-time unit (ongoing, if you will). Multiply with time and you get a measure of total energy (Wh or kWh, when talking about batteries also known as capacity). Since for batteries the voltage is a relative constant (nominal voltage), often the current multiplied with time (mAh or Ah) is used as a figure for capacity.

For example a 12V, 50 Ah car battery might supply 12, 1A (= 12 W) for 50 hours. Or 12V, 20A (= 240W) for 2.5 hours. Or anything in between. Either way, total energy contents = 12V x 50A x 1 hour = 600 Wh (0.6 kWh).

So note that the same mAh capacity figure can mean different energy contents, if the nominal voltage is different! This is why a 1.2V / 2000 mA NiMH (= 2.4 Wh) and a 3.6V / 700 mAh Li-ion (= 2.5 Wh) have roughly the same energy contents

Click to expand...

This makes things a lot clearer for me, thanks!