BT - C3100 V2.2 Universal Battery Charger Speedy LCD Display Smart Battery Charger for Rechargeable Batteries Ni-MH Ni-Cd AA AAA,3.7V Li-ion 18650 26650 17670 14500 18490 (4-Slot)

Out of the Box:The unit came with the base station, and power supply and Manual.Pros:I found these to be very well design elements of this unit both before, during and after using it:Modes: There are 5 different modes that can be selected for the unit to perform. Charging, Discharging, Refresh, Test, and Quick Test. Having this many options for your batteries is quite nice!Overheating protection: It has a temperature control monitor and a cooling fan built into the system and it does a very nice job. But that doesn't mean you shouldn't monitor the batteries. When you get a "heater" on you hands, the unit will keep dumping more and more power into that bad battery and struggle to keep the unit cool. I have a laser temperature unit to keep track of the batteries.Display: I found this very useful. you can cycle through all the settings the unit is currently set for without disrupting the process, including the current status of the process that it is doing.Current: This is my favorite part of the unit. You can charge or discharge 4 cells at the same time at 1000mAh or 1 amp for Lithium Ion cells. you are also given charging options of 200, 300, 500, 700, 1000, 1500 and 2000mAh. However for the upper charging mAh options you have to use certain slots and only 2 can be done at the same time.Voltage meter: Now I only use the voltage from my multimeter as the actual voltage of a cell. But this unit isn't dumb. If it reads that the voltage of a cell is low, it will not simple start dumping the selected mAh current you selected into the cell. It automatically drops the current down to a very small "trickle" charge until the voltage comes up enough to start putting in the selected current. I like this feature!Backlit Display: You have the option of having the backlit display on all the time or having it turn itself off after a preprogrammed amount of time.Multiple Cell options: Way too many to list here, but trust me this baby can handle all kinds of batteries.Cons:Resetting: I've not figured out what the conditions are that cause this unit to reset during the charging process. It's not over heating, or power drops or the power supply, but for some reason the unit will auto reset to the default charge settings which are 500mAh. the only thing I have figured out that overrides this is to select all the bays and cycles through the modes back to charge and setting the current back to 1000mAh. Very frustrating indeed considering how much I like this unit.Fans: While I did list this as a big Pro, it is also a Con in the fact that there is a balancing problem with how these units are manufactured. The fans will try to spin up and make a hell of a noise because they are out of balance or something. This happens multiple times until finally they start to spin up without issue. I've learned to live with it, but it is something to consider if you are planning on buying this unit.Wish List:More powerful power supply unit. The PSU that comes with the device does a good job, but it is only rated at 12DC and input of 100-240V at 50/60Hz and the output is 12v DC at 3.0A, which seems odd that it can charge at 4A. So IMO a more powerful PSU is needed.Personal experience:I'm building a DIY powerwall for my house, and I have 1000's of 18650 cells to process. I have 5 of these units working around the clock and other than the Con I listed regarding resetting (which only happens on the oldest unit) these babies do a great job!Bottom Line:Overall this product works as advertised, and performs perfectly on both large and small jobs.Recommendation:Damn Good Buy!

A few years ago, I purchased AA and AAA Nickel Metal Hydride (NiMH) rechargeable batteries from Duracell and Rayovac, along with the Duracell 2-cell quick charger. After a few months, multiple batteries showed as "defective," and I was irritated that I had a bunch of batteries less than a year old that had gone south.I decided, on a whim, to purchase this charger based on several YouTube videos and the charger's ability to test and charge cells individually. I figured it would also be a great way to test individual cells in rechargeable power tool battery packs that had failed so I could replace bad cells and resurrect the battery packs (which I have yet to do).I first decided to place two "fully charged" batteries from the Duracell charger into this charger, and was amazed to find the Duracell charger had only charged the batteries to 1.08 volts! These batteries should be around 1.5 volts fully charged, and should be charged when they drop to 900 mV (0.9 volts). No wonder I could only get about 20 minutes of intermittent use out of those batteries!So I grabbed the allegedly-defective batteries, and found their charge level to be around 0.8 volts, which is below the recommended minimum voltage. After a short while in this charger, I had 4 fully-charged batteries. I decided to run them through this charger's testing mode, and discovered all of them were at or above the rated capacity printed on them. Multiple test runs confirmed the results, so I was quite relieved to find my batteries were not defective, the Duracell charger was the problem all along!In the months since purchase, and dozens of charge cycles, all of my batteries still test perfectly with no degradation of capacity. I was even able to bring back to life some dead NiCd AAAs from dollar-store solar lights, although I would NOT recommend this charger for that purpose as the charge current is too much for repeated use on smaller cells. The charger is able to charge 18650 cells, although I have not used it for that (yet). The internal fan that dissipates heat during the battery testing feature is silent - you have to put the charger right next to your ear to hear it.The user interface is a little bit clumsy to figure out at first, but once you become accustomed to it, it's not too bad. The ability to change the display readout to show voltage and charge current is a nice feature. When batteries are fully charged, the unit automatically switches to a very low "trickle charge" to safely keep your batteries at 100% charge for when you need them, so there's no harm in leaving the batteries in the charger indefinitely.This charger now has a permanent spot on my desk, literally a foot from my computer. It has certainly earned that spot, and what I paid for the charger was cheaper than replacing all the batteries my Duracell charger falsely claimed were defective - and those new batteries would have eventually ended up in the same undercharged condition and falsely labeled as defective. In that regard, this charger essentially paid for itself.