Everything About high voltage lithium battery system

What is high voltage battery system

Currently, lithium batteries are becoming more and more popular. Especially on solar energy storage systems and UPS (Uninterruptible Power Supply) Lithium ion HV system, etc. For the lithium iron phosphate battery cells, the single cell voltage is nominal rated 3.2V, all voltage, current, power (kW) and energy (kwh) applications are based on this. High voltage lithium battery system usually refers to the battery system voltage is greater than or equal to 96V, for example, 192V 50Ah battery system is 1P60S (60 cells series connected) cell connection based on 50Ah single cell capacity, 240V 50Ah battery is 1P75S cell connection, 384V 100Ah battery is 1P120S cell connection based on 100Ah cell, etc. We also can parallel cell first for double or triple total capacity. The corresponding battery capacity is usually 50Ah, 100Ah, 150Ah, 200Ah, etc.

BMS

BMS applications between high voltage lithium batteries and low voltage BMS applications are completely different applications. Low voltage lithium battery system usually refers to a parallel application system such as 48V or 51.2V battery system. For high voltage, in the single-cluster battery system, the batteries are always connected in series to achieve a higher voltage. Moreover, there is a high voltage DC main unit is needed to manage this high voltage cluster. The main function of the high voltage DC main unit is to manage all the BMU units of this cluster through the master BMS, meanwhile to provide start-stop, protection and other functions for this cluster.

Please reference below picture for a HV lithium battery system

HV lithium battery storage system
HV 3.5U Rack Lithium battery system

HV UPS Lithium ion System

Why use high voltage lithium battery systems.

Let’s give an example for solar lithiun storage battery system field, imagine that when an 8kW hybrid solar inverter is used with a lithium battery, as a low voltage storage system, the battery DC voltage is usually 48V or 51.2V for home solar applications. Even if we use a relatively larger nominal current, such as 100A, The maximum power that the battery can provide is 5kW (51.2V x 100A = 5.12kW), and this value cannot meet the maximum output power of the inverter. Moreover, there are so many commercial energy storage applications where the power system output power is such as 30kW, 60kW, 100kW or even 500kW power capacity. In these application scenario, we must use a HV lithium battery system to lower down the discharge current.

Even more

due to the increasing power of solar PV panels and the DC voltage of inverters, the current mainstream PV panel power has increased from 300W to 400W to 600W and more, and inverters DC main bus has achieved to 1500V. Which makes the low voltage 48V and 51.2V less and less suitable for the development of the solar field.

In the solar power storage and renewable energy fields, the applications of HV lithium batteries mainly include the following:

  • High Voltage home hybrid solar and battery system

  • Commercial battery storage system 50kWh to 2mWh

  • Off grid solar system output power is more than 30kW

48v solar battery pack

Study case: HV battery storage system

Project purpose: Peak shifting
PCS: Sermatec two 60kW sermatec
Battery: OSM 345kWh LiFePO4 battery

This project is for peak shifting application especially for the market where electricity price has a big difference by timing. Battery will storage grid electricity when electricity price is cheap, usually it is night time. And battery discharges to local load when necessary. The total battery capacity is 345kWh rated at 768V, there are two sermatec 60kW pcs MA1000K60 total 120kW capacity. The full system is managed by EMS (energy management system) and system can be monitored and controlled from cloud. Please see the detailed system graphic below.

hv battery solution
120kw hybrid system

In future, when customer will upgrade this system to a solar self-consumption application. The system graphic will upgrade as the below.

120kw hybrid system

How to design a High Voltage hybrid and solar system

Please see the form below which information are necessary for customize a high voltage battery storage system.

  • Purpose: peak shifting, solar self-consumption, backup
  • Grid application: On-grid, Off-grid (fully disconnect with grid), Off-grid (grid zero export)
  • Solar generation: Yes, No
  • Battery Charging Source: Only solar, only grid, Both solar and utility
  • Power system: Single phase 230Vac, Three phase 400V, Split Phase 120/240V, others
  • PCS capacity: 20kW, 30kW, 60kW, 100kW, 150kW, 500kW, others
  • Battery Capacity: 50kWh, 80kWh, 120kWh, 150kWh, 500kWh, others
  • Environment: Indoor, Outdoor