4.2V 1A 1000mA Power Supply Adapter AC to DC Power Supply Transformer 5.5mmx2.5mm DC Plug

4.2 volt is perfect voltage for my led light project. 5 volt unit burned them out.

Used it to replace 3 AA batteries for some decorative lighting.

Perfect for my needs. Small and has not even gotten warm. It works no problems. It handles the load of charging bicycle head light battery packs easily

Note this first: it is not made clear on the product page, as of February 20, 2023, that this is not a traditional power supply, but rather a Lithium Ion battery charger. I requested this sample to use as a generic power supply for electronic projects, and discovered when I received it that it cannot supply 1.0 A at 4.2 V, which is what I was led to believe. For this I'm taking 1 star off the rating. In fact you could use this is as a power supply, if you viewed it as an unregulated (more like poorly regulated) 4 V supply, up to about 950 mA. If you try to get more current than that out of this supply, it will shut down to protect itself. See the graph with labeled "Supply Output Voltage v. Load Current" which shows output voltage ('vMeasELoad') v. output current ('iLoad'). Or, another way of viewing it, there is a graph showing output voltage v. load resistance, labeled "Supply Output Voltage v. Load Resistance".All of that being said, I think this is a pretty good, inexpensive Li-Ion battery charger, IF you use it on a battery that can charge safely at 1000 mA (the rating that you see for this charge adapter on the product page). If you have a typical 18650 battery to charge, this charger will work, but it will take somewhat longer to charge the battery than you may expect. I don't know exactly what product would use a charger like this, but apparently there are some products with a barrel jack that mates with the plug on this supply, and do not have charging circuitry inside. This is probably ok for those cases, but I'd recommend checking the specifications before using it that way.What 1000 mA actually means for this charger is that while your battery voltage is below about 3.90 V, the charger will force 1000 mA (approximately; I measured about 1030 mA) into the battery to charge it. When the terminal voltage hits 3.90 V, the charger will start reducing the current that it supplies to the battery, as it nears the fully charged state. At about 4.15 V, the LED on the charger will change from red to green, to indicate that it thinks the battery is fully charged. If you let the battery on the charger after that, some current will continue to be forced into the battery (e.g. about 100 mA at 4.20 V on the unit I tested), and eventually charging will stop at about 4.25 V (which is the voltage I measure across the charger output when it is open-circuited). See the graph labeled "Charging Profile" for a better idea of how the charger works.

Was a direct replacement for the wall charger for this type of rechargeable flashlight.

Bought to replace adapter for a LED train from target. Works well

Aside from being a plug that sits sideways, it doesn't sit snugly in the outlet and almost falls out. If that's not bad enough, the charging light doesn't work. Typical Made In China piece of s***.

I purchased the charger to recharge my flashlight . It recharged the flashlight in the expected time . It arrived as scheduled .