ISDT C4 AIR Universal Smart Battery Charger USB Type-C QC3.0 Output with APP Connection for AA AAA Li-ion Rechargeable Batteries and Fire Preventionn Material

I like this charger quite a bit. I have plenty of QC3.0 chargers around that makes this a very convenient, portable charger for my NiMH and Lithium Ion batteries. I really like that you can view details on the phone App vs. having a built in screen. I would like to see a storage/discharge feature added, but for what it does it works well and has a solid feel to it while being compact and lightweight.

First things first, I was being dumb and installed ISDT's app called "ISD Go". That is not the correct app for this charger, instead the app called "ISD Link" is the correct app for this charger. They're both by the same MFG / App company on the Play store. App is functional, allows fine tuning of charging current, chemistry, end voltage, cell capacity. It also shows real time voltage, current, and wattage coming in from the usb c port. It is missing real time graphing (or any graphing at that) but I'm sure they'll add it eventually. For $25 it's definitely the best charger out there IMO.

On powering up, was offered a firmware update. I allowed the update. Perhaps because of that, there are no manual options for charging. No power adapter is included. Using a dumb 5V/2.1A power adapter, most times could not charge 2 lithium batteries simultaneously. When it did work, charging current appeared to be only 40mA. With 4 NiMH batteries, most of the time, the app never registered charging activity and the device continuously beeped. But the batteries heated up considerably and did in fact charge. With a PD/QC power adapter, charging worked as claimed by Vendor.Bluetooth connection is iffy. Usually takes up to several minutes for charger and app to connect, with occasional failures to connect at all. Info displayed is unclear as to meaning. App shows charging voltage and power in watts. But, that info doesn't correlatate to the voltage and charging current in amps displayed for the batteries. Also, the battery voltage displayed is just wrong. Depleted NiMH batteries show as 1.3V and, while charging, may go up to 1.6V before settling at 1.4V.Batteries heat up quite a bit more than with my 3 charger/analyzers or separate chargers. Occasionally, this charger undercharges by between 100-300mAH. Basically, without a PD/QC power adapter, this device is near useless and possibly harmful to battery life. With a PD/QC adapter, it works about as well as a regular dumb charger. As such, it's overpriced for what it offers.Vendor pays for chips to support Bluetooth, PD/QC client, and heat sensors. But, they save money on 1-4 LCD screens, 1-8 switches, and a power adapter, plus the cost of assembling those extra parts. Even if the costs are a wash, I don't see that this device is worth the asking price against competing units. However, if you already have a PD/QC smart charger, this a pricey dumb charger to go with that.

I got the ISDT C4 AIR Charger to work along side my ISDT C4-evo and the EBL TC-X Pro Battery Chargers. It costs a little less than the C4-evo but it lacks more than just the nice LCD display. The only task it can do is CHARGE. No Discharge, no Analyze, no Loops and all other functions found in the C4-evo. You would think that since it uses a Bluetooth connection to connect to your Smartphone or tablet, those tasks (functions) could be easily implemented and updated/upgraded with the app. But no... that is not the case.Sorry ISDT, but this one is going back.

I REALLY dislike how Amazon places the reviews for both the C4 AIR and C4 EVO under the same listing. These are two very different products and really should have their own separate listings so the comments and descriptions are not applied to the wrong product. The C4 AIR is a nice, fast charger and I like that it has a separate wireless app to easily view the status and settings of the charger. As it is, the app basically allows you to see the charging status and can be set to alert you when your battery is fully charged. This device has so much potential with the separate app interface... what about adding configuration of test and refresh cycles and an option to charge for long term storage like the C4 EVO? As it is, there is a HUGE missed opportunity with the current minimally functional app. The C4 AIR could easily be the most popular charger available if it were to add some capabilities to its app. Because of the C4 AIR's limited functionality in its current state, I find that I much prefer my Opus BT-C2400 charger at this same price point (also purchased via Amazon.) The C4 AIR seems to charge at a rate that is a bit too high by default on its auto settings... batteries tend to get fairly warm and I am concerned this will shorten the lifespan of my rechargeable batteries. You can manually reduce the charging rate, but to what? You can manually specify the capacity and chemistry of the batteries, which is nice. In contrast, the auto / default settings on the Opus seems to keep the batteries much cooler while charging... I think the automatic charging cycle rates are better calculated on the Opus. I would think the C4 Air should be able to function similarly, especially with the app available that could possibly utilize the processing power of today's smart phones-- it's just a shame that ISDT hasn't leveraged this capability with its app. The small and clean form factor of the C4 AIR is also nice, but again, without a more functional app, I prefer the Opus.

I like this charger a lot for the fact that it is very small and can charge very fast. I like that it uses USB-C so I can use my QC/PD plugs. Like others have said, the app is very minimal. I hope ISDT adds more features and info into the app since it doesn't have a screen like the C4 Evo. Also, one bad thing I noticed is that there is an annoying buzzing sound when I charge with higher amps.3/18/23 Update: Charging seems to terminate early on my Eneloop batteries sometimes, so I am deducting a star for that. Also, really wish the app would be updated for graphs, saved profile settings for charging rates, and show voltage to the hundredths instead of tenths.