Nitecore UMS4 Intelligent USB-C Four Slot Quick Battery Charger for Li-Ion/Ni-MH/Ni-Cd/IMR 16340 14500 18650 21700 20700 AA AAA and More Batteries, with Organizer

The Nitecore UMS4 is a fantastic charger. Being able to charge four batteries at once is a huge time saver, and I’ve found that it charges them quickly while giving me confidence that everything is being handled safely. It’s perfect for keeping headlamps, flashlights, and other gear ready to go. The build quality is excellent—solid, reliable, and exactly what I expect from Nitecore. They consistently make great products, and this charger is no exception. If you need a dependable multi‑slot charger, this one delivers.

This is my second Nitecore charger, the first being the I2. Nitecore products have always been reliable for my battery charging and the digital displays are as informative as they need to be without being overly complex. The UMS4 is a great unit. Having USB C as an input makes it easy to take this charger where I need to without increasing the amount of cables and adapters I already have. The information readouts on the screen help keep tabs on charging progress, total time charging, and when it's time to retire a rechargeable battery that's been in my rotation for too long. So far I've successfully charged AA, 18350, and 18650 batteries with no issue. Similar to a 4-slot toaster, you don't always use the full capacity, but it's very nice to have when you do need it. If you frequently go through batteries, the investment in this charger and a pack of Amazon Basics rechargeables will quickly pay for itself.

Great charger that shows voltage, current, resistance and time of charging. I know of no chargers that sense between Li-ion and LiFePO4 batteries, so when charging LiFePO4 (lithium-iron phosphate) batteries, the battery type must be set manually to LiFePO4 or it will overcharge them. LiFePO4 should be charged to 3.7 volts maximum. I cannot understand the negative reviews as this is the best charger I have. I use a 45 watt PD charger with it and it charges four 21700 cells in very reasonable time for Li-ion batteries. A PD charger will give the best results. Note that it charges by monitoring current (CC) at the beginning and charges by monitoring voltage (CV) near the end of the charge cycle. This protects Li-ion and LiFePO4 batteries and charges them to 4.2 volts for Li-ion, or 3.7 volts for LiFePO4 batteries safely.

This was a much needed upgrade from my old off brand battery charger. It automatically recognizes the battery type and gives the recommended charging parameters, so all you have to do is insert the batteries and it does the rest. It has more flexibility with the usb c charger so you don’t need a wall outlet. It can charge four 21700 batteries at once and that’s what I really like about this thing.

This review is for Nitecore UMS4 I bought this to revive a battery for my TT20 flashlight that recently stopped working, and when I tested the voltage with a multimeter, it was like .03, so I figured that was the issue. This recharger was able to revive it, but it was a bit tricky. With only that battery in the recharger, it would not stay on longer than 30 seconds or whatever the auto shutoff timer is. When I put it on the charger, it was recognizing there was a battery there, but would not stay on. I was able to get around this issue, by placing another battery in a different slot, and have it charge while the problem battery was getting recharged. It took awhile, and I had to replace the extra battery that I was using to keep the unit on (swapped to another battery that needed recharging). Eventually, the battery I was reviving had enough charge for the unit to stay on, and it fully charged, and works now. Since a brand new battery of that kind (thrunite 21700 proprietary battery) was almost as much as a charger, I figured I would just get the charger and see if it works, and it did. The charger itself seems decent enough, the display was bright, and it presented all the information that I needed. I really dislike how it uses usb micro, but with all the adapters and bricks I have laying around, it's not a big deal I guess.

Best quality for the price !! Works as described ! Very Easy to use.

I have had A number of chargers, but this surpasses them all. It is intelligent and maxes out the charging speed for AA and AAA batteries that I use.

Nitecore is a very good brand. I’ve owned several over the years. My only issue with this newer model is its speed. Charging 18650 batteries takes roughly twice as long as older models.

Probably one of the best battery chargers available on the market. It stays cool even when charging all four slots, and charges very quickly. I had to return mine due to personal reasons.

Works great. I love the status screen that tells you all you need to know about battery health and how charged the batteries are