BT-C3400 With Car Adapter Universal Battery Charger Analyzer Tester for Li-ion NiMH NiCd rechargeable batteries

User interface is very easy to understand and the batteries never get hot because the charger monitors the temperature and decreases the charging current appropriately as needed. One of the few that contain a fan for cooling. The fan is extremely quiet. I really like this one with the 12 volt charger for the times I am remote and need to charge my 18650 batteries I use for caving.

Nice little unit. I checked out many YouTube videos before I bought this and it seems to perform just like people showed it. The Discharge Refresh function is very nice to condition your batteries right up front to get the maximum capacity of your new rechargeable batteries. Intuitive display. Quiet fan, (at least on this newer model) BT-C3400. It's simpler than I thought it would be after I toggled through the settings. Car adapter is also a nice Plus. Internal resistance testing is all over the place for numbers but that was explained in the manual as normal I guess. Charts show NiMH batteries should be around 25 MilliOhms but my Eneloop pro AAs never show under about 80-150. Even higher with AAAs .

The bad:Having read numerous reviews for this charger and the overwhelming recommendations, I purchased this charger without asking how many 'C cell' batteries this charger is capable of charging at one time. The answer is TWO! I suppose you could say I didn't do enough research or read through each and every review to uncover an answer I didn't know I needed to ask! Unfortunately that answer turned out to be a show stopper for me because I own and charge 24 C cell batteries. I'm extremely disappointed that I have to return this charger because the design limitation was not identified on Amazon's product page, or that the Opus Engineer(s) decided it would not be practical to widen the charger body <1/2". Seriously, who would have thought you could only charge two batteries in a four slot charger!The good: This charger rocks!! Plenty of reviews out there explaining all the useful and beneficial features this charger offers.Attn Opus: FIX your DESIGN FLAW and I will re-purchase this charger immediately!!

This seems to work as advertised, though the mAh rating measurement seems to be consistently 15% higher on these than, say, a SkyRC B6AC v2 performing the same tests on the same cells.My only concern so far is regarding build variation. I ordered two of them, and while they both appear to be identical on the outside, they behave somewhat differently in terms of thermal control. They both appear to stay around the same temperature, within a couple of degrees. However, one has a VERY loud fan that's on almost all of the time. The other has the same size fan that kicks on now and then but is very quiet when it does so. Otherwise, they seem to perform identically, and they do perform as advertised.My only gripe is with the software, and it doesn't prevent the devices from operating as expected. When the Charge Test cycle is finished, it will cycle from displaying "FULL" to displaying the battery capacity measurement in mAh. It will cycle to "FULL" on a set timer, and regardless of whether the user is providing menu navigation inputs to see other data on slots that are still running, so it's a race to tap the Display button fast enough to maybe get a glimpse of the data the user wants to see. Also, randomly, a slot will just get stuck saying "FULL" and not cycle to other data automatically, and the user must fight the timer to see the rated capacity. In this case, the capacity is the LAST thing in the Display list,Since those are the worst things I have to say about this device, I recommend it to anyone who is in the market for a multi-bay multi-function charger that can test for battery capacity. Mine have already paid for themselves by showing me the true capacity of a number of my cells are not what some sellers claim.

Catastrophically died after 18 Months!!While charging 2- 5000 milliamp C cells I notice the display light stayed lit, then the display went blank.It’s a good thing I was sitting at my desk, watching it, because apparently the microprocessor In the charger froze. It tried to full charge the C cells at full current, even though the batteries were already fully charged.If I have not been there, I'm sure the cells would have exploded!!When I noticed I had a problem, I disconnected the power supply, then removed batteries.The C cells were so hot I couldn't hold on to them.Now It’s dead and shorted!!I suggest that between charging's, you should disconnect the power supply (To reset the microprocessor In the charger) then insert the batteries first!then reconnect the power supply last, before setting the charge rate.When I first received the unit the fan squealed loudly,I had to Remove the fan and remove the plastic sticker over the bearing then add a drop of oil to the bearing to fix itPoor quality control!$54.95 right into the garbage!I'm not happy.

Worked great until it Failed after 9 months, no response from the Manufacturer about a warranty replacement although it's supposed to be covered for 1 year. I wrote to the email listed on the paperwork for warranty claims, it came back as no such address. Went to the website for the email address and it forwarded to another that says its is DC Workshop. Filled in their warranty form a couple of weeks ago and still haven't heard back. I just bought a PowerEx MH-C9000 to replace it. Been using Maha (Powerex) gear and batteries for years and happy with them. I considered on of the Nitcore chargers but their charge rate is too slow for me, I don't always have hours to charge my batteries.