. Pylontech has indicated that between the new installations of  US2000C y US3000C there are a few cases where the modules make a buzzing sound with the alarm illumination on permanently after a short period of time after installation.

The main cause of the buzzing sound along with the alarm illumination is that the modules have experienced an overload above 55Vdc or that the power supply device in the BMS is damaged, which has triggered the secondary protection elements deployed in the BMS. In either case, a replacement of the BMS is required.

During further analysis by  Pylontechit was found that in all cases the modules had been overcharged above 55Vdc. This is mainly due to the communication between the inverter and the battery not having been established correctly.

Two major changes to US2000C / US3000C that will affect the quality of external communication are highlighted below.

Add Pylontech US2000C / US3000C Switch Settings

Based on the new BMS design, the ADD switch is deployed in reverse.

This means that if previously for US2000C / US3000C, the inverter required the entire ADD switch to be in the DOWN position, now in US2000C / US3000C it will change the entire ADD switch to the UP position. The default ADD switch setting is all in the UP position.

Dip1: RS485 baud rate: 1: 9600; 0: 115200. After the change, please reset the battery.

Dip2: Resistance of the CAN terminal on the BMS side. 1: NONE. 0: connected. After the change, it is not necessary to reset. In single group, please keep the position of dip2 ar 0. For multiple groups, please refer to the operation manual.

Dip3-4: Inverted.

If no RS485 baud rate change is required or there are no multiple groups, do not change the default ADD switch settings, otherwise communication with the inverter will be affected.

Pylontech US2000C / US3000C Communication Cable Configuration

Following the table below, please make sure that in any case Pin 1/2/3 on both ports A/CAN and B/RS485 is NULL. Otherwise, the communication quality will be affected.

Please also note that the GND pin order has changed from Pin2 (US2000 / US3000) to Pin 6 (US2000C / US3000C).

For direct pin communication inverter, please make sure that Pin 1/2/3 of the communication cable are NULL. Or alternatively order the correct communication cable or external cable kits which can be purchased from Techno Sun.

For the cross-pin communication inverter, please make sure that you faithfully follow the pin order and requirements defined above to make the cable. It should be noted that because pin 1/2/3 will be NULL, part of the prefabricated cross-pin communication cable supplied by the inverter manufacture is not valid.

Apart from the above two points, for some inverter operation interface also supports manual adjustments of the operating voltage on the battery module. In lithium battery operation mode, this kind of manual settings can be followed in case the communication with the battery is lost. Please make sure that the charge cut-off voltage is set to 53.2 - 52.2 Vdc, the discharge cut-off voltage is set to 45.5 Vdc or higher for US2000C / US3000C.