LiFePO4 is usually rated at 3.2V as nominal, not 3V.
You can find a lot about it on my website.
Good video CRC…. 
I’m new to ‘fancy’ flashlights and especially the batteries used to power them and the more I read the more paranoid I’m getting about the batteries. Im sorry if some of the questions have been asked before but obviously there’s a lot of posts to sift through.
I have ordered an Astrolux EA01s which is capable of 11000 lumens and I have been told I will need a battery with around 30A continuous discharge to be able to power the 11000 lumens so I’ve bought the Samsung 40T. This battery is unprotected but have been told that the Astrolux has built in protection to prevent over charging and overcharging and therefore minimising the risk of fire or explosion (I plan on using the flashlight’s inbuilt charging).
Would having a protected battery reduce the risk further or will it not make any difference being as the flashlight has protection? If it adds more protection the most powerful I’ve found has a continuous discharge of 15A. I assume this would be fine up to around 5000 lumens, what would happen if I accidentally switch the flashlight onto turbo (11000 lumens) would it potentially damage the battery and/or risk causing a fire/explosion or would it simply just not reach the top luminosity but the battery would be fine?
Lastly what causes a li-ion battery to over discharge?
Any help would be greatly appreciated.
> battery is unprotected but have been told that the Astrolux has built in protection
if true, all good
> Would having a protected battery reduce the risk further
no
> what would happen if I accidentally switch the flashlight onto turbo
sudden darkness as the current demand would trigger the protection and trip the fuse on the battery. It will read 0 Volts on a meter after that happens.
> what causes a li-ion battery to over discharge?
falling asleep with the light on, in a light that has no overdischarge protection while using an unprotected battery
basically, lights with built in overdischarge protection, can use higher drain rate batteries to get higher outputs, using UNprotected batteries, so they dont shut off suddenly
at more modest, sustainable, output levels, a Protected battery, with much lower maximum drain rate capability, will power a light used at indoor brightness levels, just fine.
There are lights that can use both primary batteries and LiIon… the primaries operate at lower voltages. The dual fuel lights, do not have Low Voltage protection. Instead the operator is responsible for choosing Protected LiIon, when they dont use Primaries…
there is also a subset of LiIon users, who choose to run Unprotected batteries in Unprotected lights… that requires some diligence, including checking battery voltage by hand, and not falling asleep with the light on 
btw, respect for you doing your homework… enjoy your lights
Thanks very much for taking the time to reply with such a detailed response. When you say that trying to run too much power through the battery causes it to trip the fuse and read 0V does this effectively mean the battery is ‘dead’ and will need replacing?
With regards to the flashlight having protection, it’s very difficult to know 100% as their website has no data, however a couple of reviews say that it has inbuilt protection which makes sense being as it has inbuilt charging. I have just emailed Astrolux to double check, especially regarding the overdischarge protection.
> trip the fuse and read 0V does this effectively mean the battery is ‘dead’ and will need replacing?
on a protected cell, the battery fuse gets reset when the cell is placed on a charger. No need to replace.
as far as whether your light has overdischarge built into the driver, one way to find out is to run the battery down, until the light turns itself off, and then measure the voltage of the battery. We want the voltage to be above 2.5v, after the light stops working.
caveats, when draining the battery, use an output level that does not overheat the light… (it may have thermal step down to prevent overheating). Do not use Turbo repeatedly, as this increases the heat level inside the circuitry… instead use a longer slower discharge process, at a medium output.
I dont actually know the features of your specific light, but, I appreciate that you listed the model, so we can search for relevant facts.
I googled your light, found this
“This flashlight has a built-in low voltage protection (LVP)”
also this:
“I tried a 78 mm long protected Acebeam 21700 and I couldn’t screw the tailcap on”
based on those, I would not try to use protected cells
Thanks again, much appreciated. I feel much happier about it now. The flashlight runs Anduril and this can measure the battery voltage so I will check this periodically once the battery has drained to ensure it’s not dropping below 2.5v
> The flashlight runs Anduril
then it definitely has LVP… you need not worry, it is not necessary to use protected cells
the Anduril battery level indicator is also very useful… you have a light with an excellent battery safety feature set. The UI also incorporates thermal step down… another good thing…
some charging voltage tips
LiIon like to be recharged when they are about half empty… any time they go below 3.7V
you can go lower, down to 3.0V, if necessary at the time… but deep discharge does not actually help a LiIon battery…
the LVP will probably shut the light off when voltage drops below 2.7v…
about the battery meter in Anduril… it may be slightly off, by maybe 0.1v too high or too low, compared to a standalone DMM (Digital Multi Meter)…
The Anduril battery voltage display can be calibrated more closely if desired
enjoy your Anduril light!
Just noticed something on my Anduril light with a protected cell and then put an unprotected 30q in and got a similar result. Saw this a time or two and thought it was a glitch. Now it seems consistent and am wondering if anyone can explain it. Here is what happened:
With the protected cell in the light I did a voltage check and got 3.9. Then I ran it on turbo for 30 seconds and ran a voltage check again. This time the voltage read 3.2 on the first pass and 3.9 on the second pass. Put an unprotected 30q in and did a voltage check and got 4.1. Ran it on turbo for 30 seconds and the voltage check gave me 3.4 on the first pass and 4.1 on the second pass. After writing that, with the 30q still in the light, I ran it on turbo for 30 seconds again. This time I took the battery out and put my meter on it and got 4.0 something settling on about 4.08. The number 3 did not come up on the meter at all. Put the battery back in the light and got 4.1.
battery voltage under load, or immediately after a load (turbo), is lower than the “at rest” voltage
the battery voltage rebounds after resting
so, when I want to know battery voltage, I reference the “at rest” voltage, not the “at turbo” voltage…
Running on turbo puts a high current load on the cell which causes the cell voltage to drop as it gets pulled down; when you release the load you will get a bounce-back in the voltage as the cell recovers. This is a normal condition in a good cell. It happens fairly rapidly so you wouldn’t be able to remove the cell quick enough to see the droop on the DMM.
Thanks once again. I don’t have a multimeter so will rely on the Flashlight, however I will ‘assume’ that it is reading 0.1v too high to be on the safe side.
I don’t understand the relationship with volts and amps in a battery yet, but plan on doing more research. I understand that a battery may have a capacity of 5Ah/5000mAh, and that if you use a device that uses for example 5A the battery will last 1 hour before running out of charge, but where Volts fits into this I don’t know.
Looking at the spec of the Samsung 40T I’ve bought the nominal voltage is 3.6V, which is below the 3.7V (half charge) you mentioned. As you can tell I’m a little confused
> Looking at the spec of the Samsung 40T I’ve bought the nominal voltage is 3.6V, which is below the 3.7V (half charge) you mentioned. As you can tell I’m a little confused
you are learning quickly… I respect your focus and specific question
3.6v is the “nominal” voltage of a LiIon that charges up to about 4.1 to 4.2 volts, hot off the charger
batteries often ship at half charge, and fall below, depending on storage time…
do charge new batteries fully, before use…
Thanks again. So in this example, when fully charged the 40T will have around 4000mAh and 4.2V of charge. If I use it until the flashlight goes out it will have (hypothetically) 0mAh and say 3.0V charge, however it it goes below 2.5V charge this could potentially become dangerous?
For ‘normal’ use I plan on using my flashlight at around 2000 lumens which I believe requires around 6A, which will drain a 4000mAh battery in around 40 mins. My dog walks are around 30-40 mins in a morning meaning that I’m going to take it well below half capacity, nearly until empty. Is this going to be an issue?
> it it goes below 2.5V charge this could potentially become dangerous?
your light will turn itself off before the voltage goes below 2.5V
you do not need to worry about overdischarge, in your light
> I’m going to take it well below half capacity, nearly until empty. Is this going to be an issue?
not a problem… they are made to be used…
your light is safe,
at worst the batteries will run out and you will be left in the dark…
then simply insert a fresh battery, or turn on a backup flashlight…
once you have actual experience, you may find it convenient to lower the output to increase battery life
you may not need 2000 lumens for an hour… you might find 500 lumens sufficient, and get 4 hours
Thanks for all your help. I shall now leave you in peace
You won’t be able to run 6A with that light for 30 - 40 min. 6A is over 20 Watts at nominal voltage. I wish there were a spec for how many watts a light could dissipate but of course that varies widely depending on the temperature of the environment it is used in and how it is held. In one review the reviewer thought it could sustain 1000 lumen. Whatever the number really is I doubt it will be anywhere near 2000 lumen. If you set out to use it at that level you can feel good and not worry that you will deplete your light in a 40 min walk. Your eyes may not even notice it but unless your walk is really cold I am certain that the current draw will be cut considerably to control the temperature of the light.
> I shall now leave you in peace
lol
pay it forward 
feel free to private message me,
if you would like to brainstorm further, from time to time
I look forward to hearing your results
enjoy the walks
Are you saying that it will get too hot at 2000 lumens/6A? The reason I thought this would be OK is that a fellow dog walker uses an Exposure Diablo which apparently is 1800 lumens and it only gets slightly warm. Obviously I have nothing to measure that it’s at 1800 lumens and so it could indeed be lower than that but it’s plenty bright enough :+1: