fenix uc40 battery protection not activating when the voltage is low. help

Good day fellow cpf. I would like to ask about the battery
of my uc40 (ARB-LT1) is still continue to run my flashlight even when the battery is very low i measured in my multimeter 2.75v stil the protection is not activating. Unlike on my other battery like aw18650 the protection will kick in around 3 10v. Is this normal for the ARB-L1T battery? Thanks

Don't know what Fenix has set as cut-off point. Do recommend you charge it though
You could contact Fenix and ask them about it.

den331 said:

Good day fellow cpf. I would like to ask about the battery
of my uc40 (ARB-LT1) is still continue to run my flashlight even when the battery is very low i measured in my multimeter 2.75v stil the protection is not activating. Unlike on my other battery like aw18650 the protection will kick in around 3 10v. Is this normal for the ARB-L1T battery? Thanks

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Is your ARB-L1T NCR18650B 3.6V 3400mAh?
If so, the PCB will kick in around 2.5~2.6V. But I would like you to contact Fenix.

candle lamp said:

Is your ARB-L1T NCR18650B 3.6V 3400mAh?
If so, the PCB will kick in around 2.5~2.6V. But I would like you to contact Fenix.

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I would also expect it to be 2.5V. As the UC40 reduces the output to the lowest level as the cell voltage drops, it is only a very light load. This means the cell voltage barely drops when running and it continues to run a long long time at a very low level.

My suspicion is that Fenix designed it this way (being a rechargeable light with unusual cell design) so that instead of being suddenly left in the dark, it would fade out giving you plenty of warning to recharge. Just MHO though.

candle lamp said:

Is your ARB-L1T NCR18650B 3.6V 3400mAh?
If so, the PCB will kick in around 2.5~2.6V. But I would like you to contact Fenix.

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Yes it is. . I dont want to try up to 2.5 volts it could harm the cell

Why would you want to run it that low [2.75V] in the first place?! I usually charge mine @ 3.7V never below 3.5V.

Capolini said:

Why would you want to run it that low [2.75V] in the first place?! I usually charge mine @ 3.7V never below 3.5V.

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Of course we would not like to run our cells that low but the battery says it has a built in protection . But the protection is not tripping when the voltage is low

den331 said:

Of course we would not like to run our cells that low but the battery says it has a built in protection . But the protection is not tripping when the voltage is low

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It probably kicks in like ~2.5V like someone else mentioned.That is where most of mine do. I know you are curious to know what it is for sure.

We all can have different preferences! For me, I have NEVER let any of my batteries get even close to that low.The protection is a NON issue.

I know my flashlights in relation to whatever battery I am using. I do run time tests as soon as I get a new light so I know how long it takes before it is at 3.7v or 3.6v.

My walks are between 60 and 75 minutes. I know how long they are and how long the batteries will last! I have guessed the exact voltage numerous times when I checked them after my walk. Almost all the time within a few hundredths of a volt!

I realize everyone is not as aware of the time as I am! lol! I use my lights every night. a casual user may use it 20 minutes here, 20 minutes there ect!

Two suggestions:

1.Get in contact w/ Fenix for verification.

2. Check the voltage after you use it 20/30 or 40 minutes. Then charge it.

Anyway,,,,,,,,,all this is just how I use them and understand them!

Capolini said:

It probably kicks in like ~2.5V like someone else mentioned.That is where most of mine do. I know you are curious to know what it is for sure.

We all can have different preferences! For me, I have NEVER let any of my batteries get even close to that low.The protection is a NON issue.

I know my flashlights in relation to whatever battery I am using. I do run time tests as soon as I get a new light so I know how long it takes before it is at 3.7v or 3.6v.

My walks are between 60 and 75 minutes. I know how long they are and how long the batteries will last! I have guessed the exact voltage numerous times when I checked them after my walk. Almost all the time within a few hundredths of a volt!

I realize everyone is not as aware of the time as I am! lol! I use my lights every night. a casual user may use it 20 minutes here, 20 minutes there ect!

Two suggestions:

1.Get in contact w/ Fenix for verification.

2. Check the voltage after you use it 20/30 or 40 minutes. Then charge it.

Anyway,,,,,,,,,all this is just how I use them and understand them!

Click to expand...

Thanks capo. This is my first flashlight with built in charger that's why i'm curious

den331 said:

Thanks capo. This is my first flashlight with built in charger that's why i'm curious

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Your welcome! I hope I was a little help! I know I rambled on a bit!

Capolini said:

Your welcome! I hope I was a little help! I know I rambled on a bit!

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By the way i like your vinhs ld50 edition

I found that my pd32ue would not turn on in the morning as I was headed out to work. I didn't have time to babysit the charger so I swapped batteries and it worked. When I got home and put the battery in the charger, it initially read 2.7 volts. It charged fully and is still being used.

den331 said:

Yes it is. . I dont want to try up to 2.5 volts it could harm the cell

Click to expand...

Capolini said:

Why would you want to run it that low [2.75V] in the first place?! I usually charge mine @ 3.7V never below 3.5V.

Click to expand...

Capolini said:

It probably kicks in like ~2.5V like someone else mentioned.... I have NEVER let any of my batteries get even close to that low.The protection is a NON issue.

Click to expand...

Kueh said:

I found that my pd32ue would not turn on in the morning as I was headed out to work. I didn't have time to babysit the charger so I swapped batteries and it worked. When I got home and put the battery in the charger, it initially read 2.7 volts. It charged fully and is still being used.

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Excuse the language, but people fanny about far too much worrying about things like this. The protection circuits are designed to stop cell damage. Optimum cell care is a real pain in the butt and not worth the added cell life/performance compared to just using them and replacing them when they have degraded too much.

I don't condone purposefully damaging anything, but sometimes it is not worth being so pedantic about a percent capacity loss per year here and there. Life is too short.

In the course of my review runtime tests I regularly run cells down to less than 3V and depending on the test it can be lower. Of course the cell voltage sag under load means that the protection can trip in before the resting cell voltage reaches 2.5V (and here I am talking about all 2900mAh cells and higher capacity). If however you very slowly drain that cell and bring the voltage down to 2.5V over a long period, this is when greater cell degradation is likely. When I ran the '120 day challenge' of some Armytek lights, the cells used there got very slowly down to 2.6V and as soon as the test completed they were charged back up and in fact were capacity tested and found not to have lost any capacity.

Even if you run a cell until the protection trips, just make sure you charge it up again and don't leave it that low. You realise of course that the opposite issue exists in that if you keep your cells topped up you are also causing premature ageing.

If storing cells, then follow the guidelines of getting them to a storage voltage and store in a cool place.

But most importantly, USE your lights and cells and while not abusing them, don't be so hung up over using the capacity they have. Life is much happier if you don't obsess so much (believe me, as a certified obsessive perfectionist I know only too well).

subwoofer said:

Excuse the language, but people fanny about far too much worrying about things like this. The protection circuits are designed to stop cell damage. Optimum cell care is a real pain in the butt and not worth the added cell life/performance compared to just using them and replacing them when they have degraded too much.

I don't condone purposefully damaging anything, but sometimes it is not worth being so pedantic about a percent capacity loss per year here and there. Life is too short.

In the course of my review runtime tests I regularly run cells down to less than 3V and depending on the test it can be lower. Of course the cell voltage sag under load means that the protection can trip in before the resting cell voltage reaches 2.5V (and here I am talking about all 2900mAh cells and higher capacity). If however you very slowly drain that cell and bring the voltage down to 2.5V over a long period, this is when greater cell degradation is likely. When I ran the '120 day challenge' of some Armytek lights, the cells used there got very slowly down to 2.6V and as soon as the test completed they were charged back up and in fact were capacity tested and found not to have lost any capacity.

Even if you run a cell until the protection trips, just make sure you charge it up again and don't leave it that low. You realise of course that the opposite issue exists in that if you keep your cells topped up you are also causing premature ageing.

If storing cells, then follow the guidelines of getting them to a storage voltage and store in a cool place.

But most importantly, USE your lights and cells and while not abusing them, don't be so hung up over using the capacity they have. Life is much happier if you don't obsess so much (believe me, as a certified obsessive perfectionist I know only too well).

Click to expand...

It's not easy to replace the battery of the uc40 its a bit expensive compared to the regular 18650's.. i tried to fully drained the battery of my uc40 protection tripped in . And charged it for a few seconds to disable the protection my multimeter read 2.85 volts

den331 said:

It's not easy to replace the battery of the uc40 its a bit expensive compared to the regular 18650's.. i tried to fully drained the battery of my uc40 protection tripped in . And charged it for a few seconds to disable the protection my multimeter read 2.85 volts

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True the UC40's battery is a special design and is more expensive to replace.

Why did you want to fully drain the battery? Why were you surprised that the protection tripped in while doing so? (Once mostly depleted, the UC40 I tested ran at only the low output for a very long time giving plenty of to recharge)

2.85V is fine as long as you recharge it asap. Just don't make an intentional habit of running it down until the protection trips.

den331 said:

i tried to fully drained the battery of my uc40 protection tripped in . And charged it for a few seconds to disable the protection my multimeter read 2.85 volts

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That means your battery's protectcion circuits tripped at lower voltage (maybe 2.5~2.6V) than 2.85V you read.
Li-ion cells rebound (or recover the voltage) when the load is removed, and this amount of the voltage recovery depends on the discharge current. At high discharge current, the voltage recovery is much. At low discharge current, the voltage recovery is less.

You can refer to this thread.

subwoofer said:

True the UC40's battery is a special design and is more expensive to replace.

Why did you want to fully drain the battery? Why were you surprised that the protection tripped in while doing so? (Once mostly depleted, the UC40 I tested ran at only the low output for a very long time giving plenty of to recharge)

2.85V is fine as long as you recharge it asap. Just don't make an intentional habit of running it down until the protection trips.

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Because im using my uc40 as a night light

Thanks for the info

I suspect Fenix designed it this way as well. My UC40UE has seen zero issues