# How to measure charging current for TP4056 module?

TP4056 module is connected to usb port on my PC resistor is default 1.2k...

When I put multimetar on output of module I get about 120-130 mA... I am not sure why is that, should I get 1A?

From datasheet it say for resitor 1.2k chargin current is 1A.

Maybe I doing something wrong, anyone know what is problem?

• Did you try providing a proper load? Dec 25, 2016 at 15:59
• To module? How much it should be? Dec 25, 2016 at 16:04
• It should be one partially-discharged Li-ion or LiPo cell. Dec 25, 2016 at 16:12

When I put multimetar on output of module I get about 120-130 mA

That is the expected "trickle charge" current.

should I get 1A?

Not necessarily. You only expect to see 1A (assuming RPROG=1.2kΩ) under specific circumstances e.g. battery voltage >2.9V (VTRIKL), and that is after a short period of rising charge current, up to a maximum of 1A - see the TP4056 datasheet. If a battery is not attached or <2.9V then you would only measure a maximum of the trickle charge current, as you reported.

• So if I connect multimetar and attach also battery I some time I should get 1A? Dec 25, 2016 at 16:23
• @Vladimir - "if I connect multimetar and attach also battery [after] some time I should get 1A" - if you meant "after some time", and assuming it is a normal Li-Ion battery, then the answer is yes, if the battery is working correctly, so that the voltage across it rises as normal during charging. With a faulty battery, the answer may be "no", depending on its exact behaviour. Of course this assumes your battery is designed to be charged at 1A! Have you checked your battery's datasheet? Dec 25, 2016 at 16:27
• @Vladimir - FYI I just measured a friend's TP4056 1A module, and it charged a 2000mAh 18650 Li-Ion cell at approx. 930mA during the constant current (CC) phase. Also note that the IC will get hot at 1A charging current, and the IC may reduce the charging current to limit its own temperature. Dec 25, 2016 at 16:59

According to the datasheet, the proper way to measure charging current would be to put your multimeter probe at PIN 2 (the charge current monitor pin) of the TP4056 and measure the voltage. The current can then be determined using the formula below:

$$I_{bat} = \frac{V_{prog}}{R_{prog}} \times 1200$$

By default, the R_prog would be 1k2 ohm resistor and thus you would have a 1:1 relation between voltage and current. So if you measure 1V at PIN2, you have 1A of current charging the battery.

I don‘t know about this particular chip, but I had issues with measuring the charging current on the battery side before. It turns out the burden voltage of the multimeter confused the system, so I resorted to measuring the current on the input side.