It may be very frustrating that you find the lithium battery pack can’t be charged and don’t know how to fix it. In fact, there are 3 main reasons cause this failure and we can test and test what is the real cause, then fix it accordingly. Here you can learn and discuss with us.

There are two simple methods for determining the problem of the lithium battery BMS.

Firstly, directly charge the lithium battery pack without the BMS, that is, the B+ and B- of the lithium battery pack are directly charged. If it can be charged, it can ensure that the lithium battery pack does not pass through the BMS. When the BMS is charged, it cannot be charged, which indicates that the BMS of the lithium battery is faulty.

Another way is to replace the BMS. If the new BMS is replaced, it can be charged, but the old BMS cannot be charged, which means that the BMS in the previous lithium battery pack is faulty.

If it is the problem of the lithium battery BMS, most of the charging MOS of the BMS is faulty, the charging fuse is broken down by a large current, or the IC of the lithium battery BMS is damaged.

The failure of the lithium battery BMS makes the lithium battery pack unable to be charged. The most direct solution is to replace a new BMS.

If there is no completely new BMS, you can detect the specific failure points of BMS, such as MOS tubes, resistors, capacitors, ICs, fuses, and other components, detect the specific failure points of the BMS, and then replace the elements of the BMS accordingly. the device, or PCB circuit, it can be solved.

This reason includes the internal process of the lithium battery pack and the charging circuit. The packing process includes virtual soldering during soldering, rust and disconnection of the series nickel strip, and short circuit in the assembly circuit.

The way to determine the problem of the packing process is to disassemble the lithium battery pack, observe each process point with the naked eye, and perform a charging test after basic observations such as false welding and false welding, so as to quickly determine whether the lithium battery packing process has a problem or not.

The process problems of the charging circuit, including the defective plug and the defective welding wire of the plug, etc., for example, the DC head is the charging port of most small power lithium battery products. This leads to a problem with the charging circuit of the lithium battery pack, and the lithium battery pack cannot be charged.

Re-weld the position of false welding and false welding. If it is a charging port problem, replace the charging port and re-solder it.

If it is the battery cell that causes the lithium battery pack to fail to charge, there are two ways to judge:

One is to charge each string of cells in the lithium battery pack. If there is a string of cells that cannot be charged, it means that the cells of the lithium battery pack are faulty, and it is determined to ask the lithium battery cell problem!

The other is that each string of cells can be charged, but the voltage difference between each string is relatively large.

We also say that the consistency of the lithium battery pack is relatively large, which will also cause the lithium battery pack to fail to charge.

If the voltage difference between each string of the lithium battery pack is large, it can also be determined that the problem of the lithium battery cell has caused the lithium battery to fail to charge.

For example, in a ternary lithium 36V battery pack, a combination of 10 strings, if the voltage of one string of cells is 4.2V, and the voltage of other strings is about 3.0V. When the charger is charging the lithium battery pack, although the other strings are about 3.0V and the voltage is very low, the 4.2V string will instantly reach the overcharge protection value of the lithium battery protection board during charging, and the protection board will It will start the overcharge protection and disconnect the charging MOS tube, resulting in no charging.

If the battery cell cannot be charged, it needs to be replaced; if the voltage difference between the cells is large, the voltage of each string of cells in the lithium battery pack can be leveled before continuing to charge.

If you have any problem with the lithium battery pack not charging, welcome to contact us for a discussion.