Testing Li-ion batteries. Checking batteries for authenticity

Goals and objectives

Check batteries from world brands for compliance with the declared characteristics.
Check the authenticity of Li-ion batteries sold on marketplaces by suppliers from China.
Check to what extent the rating and review system on marketplaces can serve as a basis for choosing a product.

Process

We select batteries from well-known brands and large suppliers with a large number of positive reviews and high ratings on trading platforms.

Batteries are divided into two groups:
the first group – batteries from suppliers from China;
the second group is batteries from large international brands.

Batteries are tested with maximum permissible currents. The complex internal resistance is measured. Analysis of results.

A reference battery will be added to each group for comparative analysis.
Reference battery – a battery with conditionally reference parameters, known to be genuine and without manufacturing defects.

Let's explore the first group

LiitoKala and EAIEP batteries are trying to imitate the Korean LG HG2 LGDBHG21865. Not only the color and shape of the contacts are repeated, but also the markings. Both batteries are marked as “DBHG21865”, but in place of the “LG” symbols there is a sticker with the LiitoKala or EAIEP logo. This is probably done to avoid blocking by the marketplace.

Figure 1 - Appearance of batteries — Figure 1 – Appearance of batteries

Table 1 – Battery characteristics

Name	Nominal capacity declared mAh	Maximum discharge current stated A
LiitoKala	3000	25
EAIEP	3000	25
LG	3000	20

Measurements

The characteristics of LiitoKala and EAIEP batteries indicate a maximum discharge current of 25A.

Since the maximum discharge current of the LG reference battery is 20A, measurements will be made with a current of 20A.

Test mode:
– discharge current 20A;
– direct current discharge;
– minimum discharge voltage 2.5V.

Graph 1 - Test with current discharge 20A — Graph 1 – Test with current discharge 20A

LiitoKala and EAIEP batteries exhibit an avalanche-like voltage drop.

The EAIEP graph ends at 905mAh. This is due to the activation of the emergency pressure valve. The battery is irreversibly damaged.

It is obvious that the real parameters of LiitoKala and EAIEP do not correspond to the declared ones.

If you repeat the test with a current of 2A, then the LiitoKala and EAIEP batteries show the result within normal limits.

Graph 2. - Discharge current test 2A — Graph 2. – Discharge current test 2A

That is, these are indeed batteries with a capacity of 3000 mAh, but they are not high-current. Under the guise of high-current batteries, ICR batteries are sold that are designed for a discharge current of no more than 3-4A.

Internal resistance

The complex internal resistance of a battery is one of the most important parameters. The higher the resistance, the greater the losses, the higher the heating and the lower the discharge current the battery can provide.

Measuring internal resistance allows you to determine in absentia the maximum power of the connected load. For high-current batteries, the internal resistance usually does not exceed 18 mOhm.

Let's measure the internal resistance of the batteries.

Table 2 – Internal resistance

Name	Internal resistance, mOhm
LiitoKala	28
EAIEP	35
LG	15

Now if you go back and compare schedule 1 and Table 2, then a correlation between the internal resistance and the discharge graphs will become noticeable. Resistance of 28 and 35 mOhm exactly corresponds to ICR batteries. That is, the version of “repackaging” inexpensive ICR batteries into expensive high-current ones is confirmed.

Misconception

Most household chargers and measuring devices measure a discharge current of no more than 2A. And as we see on schedule 2, at such low currents, even fake batteries show the declared capacity. This creates the illusion that the batteries are genuine.

However, when using batteries in real devices, where the current consumption can reach 20-30A, the battery is destroyed or rapidly degrades.

Manufacturers of cheap cordless tools can use just such batteries in their tools. As a result, batteries quickly lose capacity or fail. This means that fast charging “kills” the batteries, in the cold the capacity “leaks”, and so on.

Although this is all due to the use of batteries in modes for which they are not intended.

Let's explore the second group

Batteries: Skilhunt BL-135 PCB, 3500 mAh HD PCB and KLARUS 3600mAh PCB
(hereinafter referred to as Skilhunt, Olight and KLARUS).

Figure 2 – Appearance of batteries

All of the listed batteries are equipped with an electronic protection board, that is, they are not a cell in its pure form. Essentially, this is an electronic device consisting of a Li-ion battery and a control board.

They are made on the basis of a Panasonic NCR18650GA battery (hereinafter referred to as Panasonic). This battery will be the reference one.

Measurements

All batteries, with the exception of Olight, showed results that were poorly distinguishable from the reference Panasonic.

Graph 3. - Discharge current 5A — Graph 3. – Discharge current 5A

Table 3 – Battery parameters

	Declared capacity mAh	Capacity measured (5A), mAh	Maximum discharge current, A	Internal resistance, mOhm
Panasonic	3450	3378	10*	23
Skilhunt	3500	3351	8	31
Olight	3500	3248	10	46
KLARUS	3600	3356	7	27