Test/review of USB LiIon Charger BH-042100-02U

USB LiIon Charger BH-042100-02U

This is a cheap LiIon charger from Ebay, does it work?

I got the charger in a envelop from Ebay dealer: buybtyhere

It included the charger and a thin USB cable.

The USB power connector is placed on the back of the charger.

The user interface is a led for each slot, it will show red while charging and green at all other times.

The back has the usual label with specifications, but they are not very precise.

The connection are the common slider style that can handle from 31.5mm to 69.5mm, this means a few protected 18650 will not fit and the new xx700 will not fit.

The charge current is on the high side for small batteries and of course the voltage is too high for all batteries.

Measurements charger

  • When not powered it will discharge the battery with less than 0.01mA

  • Charge always charges from a constant voltage of 4.316 volt on slot #1 and 4.286 volt on slot #2.

  • Led changes to green at 4.284 volt on slot #1.

  • Power consumption when idle is 5mA from USB

The charging is a rather bad CC/CV charge curve around 600mA and the charger never terminates, instead it charges to 4.3V. The charge circuit goes into oscillations at one point during the charge (This is probably a combination of voltage and internal resistance of the battery and do not show up on my other curves).

Slot \#2 is similar, but it do not oscillate, it is slower to charge and have a lower termination voltage, but still way to high.

I did not try with a lot of batteries, due to the high voltage. This cell was charged in a similar way to the above.

Simulating a long cable or a weak charge do not affect the charger much

The charger maintain same charge speed with two batteries.

M1: 34.2°C, M2: 35.2°C, M3: 44.5°C, HS1: 49.9°C

HS1: 45.6°C

There is a constant current generator for each slot inside the charger, it will use a low current for fully discharged batteries.


What is inside this type of cheap charger? The bottom was five screws and the circuit board was one screw.

Not much on this side, only two dual color leds and the battery connection.

Not much on this side either, only one unmarked chip for each slot. Each chip has two resistors and two capacitors.


This is not a very good charger, the main issue is the high charge voltage and the secondary issue is that it never terminates.


The charger was supplied by a reader for review.

Here is an explanation on how I did the above charge curves: How do I test a charger