Safe to charge k2 lfp123a on a Nitecore UM10?

BugoutBoys

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I just got some k2 lfp123a for my Surefire single cell Aviator and the batteries say they are 3.2V but after I charge them with the UM10, they are at 4.1V then slowly go down to 3.6V where they settle. Is the charger overcharging them? Do I need a different charger given that they are 3.2V not 3.7V?
 

vadimax

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They didn't explode yet? Strange... :D

You need a charger capable to terminate at 3.6V. Charging them to 4.2V you may end up with this:

 
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RobertMM

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You definitely need a charger with a 3.6V setting.

LiFePO4 are more tolerant of abuse but overvoltage will decrease lifespan. K2 cells aren't cheap. :)
 

BugoutBoys

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You definitely need a charger with a 3.6V setting.

LiFePO4 are more tolerant of abuse but overvoltage will decrease lifespan. K2 cells aren't cheap. :)
Can you recommend a charger? Hopefully one that doesn't break the bank. As much as I know about flashlights, my battery/charger knowledge is in the negative percentage :naughty:
 

ChrisGarrett

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Thank you so much!!

I've got two of the Liitokala 100s and two of the 202s. I think I got all four for $22 shipped from GearBest, so they're cheap enough to pick up a few and stash them in various places, or keep them as spares.

Just an FYI: both of my single bay 100s, slight overcharge (4.22v-4.23v) and both of my two bay 202s slightly undercharge at 4.18v-4.19v, but they're very small and quite flexible. Those voltages are all within spec for the 6 bays.

Chris
 

IonicBond

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If you haven't done so, discharge the cell immediately.

This is a classic example of where the notion that "LFP is more tolerant of overcharge" comes from. Tolerant in the fact that they don't blow up when you overcharge them by 500 millivolts, but the damage has been done to the cell nevertheless - internal resistance skyrockets.

In the future, don't do that and be very mindful of the nominal voltages of LFP compared to other lithium chemistries. Ie, a "nominal" 3.2v LFP does not want to be charged more than 3.6v per cell.

So lfp being "tolerant" as in not immediately blowing up and burning down your house like other lithium chemistries? -yes-, but the actual *damage* to the cell's performance is extensive.

A fully charged LFP cell when measured after 12 hours rest, should be near 3.38 to 3.4v ... resting. If it is resting any higher than that, you've overcharged them and destructive secondary reactions are taking place.
 
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BugoutBoys

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This is a classic example of where the notion that "LFP is more tolerant of overcharge" comes from. Tolerant in the fact that they don't blow up when you overcharge them by 500 millivolts, but the damage has been done to the cell nevertheless - internal resistance skyrockets.

In the future, don't do that and be very mindful of the nominal voltages of LFP compared to other lithium chemistries. Ie, a "nominal" 3.2v LFP does not want to be charged more than 3.6v per cell.

So lfp being "tolerant" as in not immediately blowing up and burning down your house like other lithium chemistries? -yes-, but the actual *damage* to the cell's performance is extensive.

So I have only charged each of them ONE time on that charger. What do you think the affect is so far? With only one charge. In the future I will definitely only use a 3.6v charger haha
 

IonicBond

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The effect of increased internal resistance means that they will now self-discharge faster, and the voltage drop under heavy load will crash much sooner. They may appear to have lost capacity / runtime. They haven't really, but *access* to the cell's material is restricted internally with secondary reaction garbage layers.

You may get some life out of them, but typically what happens is that one day they seem perfectly normal, and then one charge cycle later, they are dead. There's plenty of material left, but the SEI layer just closes down. Much like wiping up a gravy spill with a brand new sponge. Plenty of sponge left, but the pores are so clogged that it no longer functions.

Fortunately, your cell is inexpensive. Had this been done to a 200ah prismatic that would have been a much larger story. :)
 

BugoutBoys

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The effect of increased internal resistance means that they will now self-discharge faster, and the voltage drop under heavy load will crash much sooner. They may appear to have lost capacity / runtime. They haven't really, but *access* to the cell's material is restricted internally with secondary reaction garbage layers.

You may get some life out of them, but typically what happens is that one day they seem perfectly normal, and then one charge cycle later, they are dead. There's plenty of material left, but the SEI layer just closes down. Much like wiping up a gravy spill with a brand new sponge. Plenty of sponge left, but the pores are so clogged that it no longer functions.

Fortunately, your cell is inexpensive. Had this been done to a 200ah prismatic that would have been a much larger story. :)

Wow, that's intense! Well thanks for the info!
So already, even after one charge with the 4.2V charger, I should probably replace them at this point?
 

vadimax

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Wow, that's intense! Well thanks for the info!
So already, even after one charge with the 4.2V charger, I should probably replace them at this point?

I guess not. Of course, you've made some damage that might reduce battery lifetime, but if they charge without overheating with a proper charger they are OK to be used.
 

bykfixer

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The NiteCore D2 and D4 chargers have a LifePo4 setting.

It runs nice n cool, has a digital readout to show progress and can charge triple a sized all the way up to C sized along with those 65(0) length cells.

Good charger for the money.
 
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