Hi all. I’m a newbie here so please be gentle if I make any errors.
I recently bought a Nitecore UMS2 charger from OpticsPlanet specifically for the purpose of charging some LiFePO4 batteries. It has a mode for this. I discovered that it can overcharge these batteries, which can cause a fire hazard. I posted a negative mini review on OpticsPlanet and Amazon which contains a bit more detail than I’m posting here. Links below.
There are two bottom lines.
1) If you just put a LiFePO4 in and leave it alone, it starts charging to 4.2 V rather than 3.7 V. This will overcharge the battery.
2) On two occasions, I had a LiFePO4 battery charging and I had specifically gone to the trouble of setting LiFePO4 mode and checking it. In one case, I looked later and the battery was at 4.13 V. In another case, the unit had changed to Li-Ion mode and was set to terminate at 4.2 V.
I returned the unit and am considering other options. I cannot provide much more detail than what’s here and what’s in the reviews. (These are not full reviews. Just one paragraph.) But, I wanted to pass it along in case the information would be useful to someone.
If you charge LiFePO4 in this charger, you must set the mode properly, check it, and in my opinion, babysit it. Other reviewers have complained about other things, including (they say) a weak mechanical connection to the USB connector in the case.
This sounds really familiar. See my similar thread on Xtar charger doing the same thing: My Xtar VP2 will overcharge
Fortunately LFP is pretty safe, and if a charger that’s been OK suddenly starts doing this, I think the risk is low. But I sure wouldn’t keep using it. Desertcat in my thread has come to the conclusion that the CV function of the charger is too high for LFP throughout the entirety of the charging cycle, and if that’s what’s happening, the cell life may be shortened even if you babysit it.
achilles’ spiel I read through the other thread and that is interesting. Also interesting coincidence that we should discover similar things about the same time. I wonder if the two chargers are using similar circuitry and firmware under the covers. I would hope the power control logic doesn’t keep the battery connected to voltage after the charging cycle. That would be a really bad flaw.
The only LiFePO4 batteries I have are some RCR2’s and some RCR123A’s which I discuss in this thread about draining them to exactly 3.25 V - 3.30 V to make them safe for devices that use CR2 or CR123A primaries.
The little Soshine charger that came with the RCR2’s works fine but it only goes up to 16340 in size. I’ve been eyeballing the SkyRC MC3000 but it’s way overkill for what I’m doing. It’s unfortunate that some of these cheaper chargers apparently have dangerous defects. Ron
Yes. Same problem.
I set the LiFePO4 mode, the charger shows that the LiFePO4 mode is on, but the battery charges up to 4.2V. Not once did it work correctly in LiFePO4 mode.