Application Solution: LUNA2000 Battery Safety & Reliability –Modular+ 4 Layer Safety Protection
With the increases in the electricity price nowadays, PV become a more and more popular solution to
reduce the electricity cost and ensure energy security. However, recently residential ESS has brought a
lot of concerns on safety after some news:
- Senec remotely switches off its residential batteries after explosion in Germany
- Leclanché battery cell fab returns to full operation after fire incident
- LG Energy recalling battery systems in Australia due to fire risks
With millions of Battery Systems installed worldwide, precautions should be taken to ensure safety. For
a battery system, the safety issues of the battery cell are the main course of battery safety design.
Thanks to the Modular+ design, Huawei Smart String ESS can provide 4-layer safety protection (Shown
in Fig 1) to give a safer solution to installers and house owners.
Layer 1 LFP Battery Cell:
How to find the more suitable type of battery cell for Residential Battery ESS?
Nowadays, two of the more commonly used lithium-ion chemistries--Nickel Manganese Cobalt (NMC)
and Lithium Iron Phosphate (LFP)--are considered in detail here. For Residential Battery ESS, Heat
generation behavior is of great significance for the safety design.
Thousands of tests and Data Analysis to find the best - LiFePO4 (LFP) Battery Cell
Huawei Global Compliance & Testing Center (GCTC) (Shown below) has the most complete simulation
and the real test for products in all scenarios. All the products need to pass the strictest test of Huawei
For battery cells, there are two figures that are important to safety: heat generation during
charging/discharging time and the temperature when battery thermal runaway occurs. Having done
thousands of tests, the comparing thermal behaviors of different types of lithium-ion batteries are
shown below (Fig 3). And it is not difficult to find out that LFP which generates low heat during
charging/discharging and has a higher temperature when the battery starts thermal runaway. That’s the
reason why the NMC battery, another popular battery type, has higher energy density and power
capacity, but Huawei Smart String ESS (LUNA2000) still chooses LFP for a safer Residential ESS
Huawei Battery Cell Certificate:
Layer 2 Cell-Level Monitoring:
How do we provide a precise monitoring method of battery cell temperature?
While it’s well known that battery cells need careful monitoring and management to ensure effective,
reliable, and safe operation and the series-connected stacks of many tens of cells or more require more
attention from designers, particularly as the number of cells per battery increases.
Huawei Solution: 4 Times Monitoring Resolution than conventional solution
Huwei Smart String ESS LUNA2000 has 16 battery cells and 8 sensors per pack as a result each sensor
works independently and monitors only 2 cells. Compared to conventional solution which only has 2
sensors per pack, Huawei provide cell-level temperature control and achieve higher monitoring precision.
Layer 3 Galvanic Isolation:
How to protect the battery cell from electrical noise from PCS side?
Unlike other electrical parts, battery cells are more sensitive to electrical noise. Voltage rises or harmful
harmonics can damage battery cell and cause fire. So it is significant to separate the input and output
supplies to a device so that energy flows through a field rather than via electrical connections, like the
isolation transformer in PV power plant.
Huawei Solution: Safer Electrical System: Galvanic Isolation
Compared with conventional battery system which all the battery cell are directly connected to PCS,
Huawei Smart String ESS use galvanic isolation to protect battery cell. The galvanic isolation (Shown
below) is a method of isolating functional sections of electrical system to prevent current flow; no direct
conduction path is permitted. Energy and information can still be exchanged between by electromagnetic
waves (Isolation Transformer). If the isolation transformer is located between the PCS and the battery
cell, anything generated by the PV or Grid is isolated from the PCS, while anything from the battery cell
will also be isolated from the other side.
Huawei Smart String ESS Certificate:
Layer 4 Self-extinguish Pack:
Under emergency, how to provide superior safety method to house owner?
With millions of ESS installed worldwide, this technology is designed to be relatively safe and reliable. But
precaution should be thought in advance to ensure the safety of family. For real emergency, fire
extinguishing method will be the most important thing. It is not difficult to find out that self-extinguish
method will be the best option for Residential ESS because of two advantage: Fast (no need for external
fire extinguisher & precise fire suppression in a small area) and high reliability (Inside the Battery pack).
Huawei Solution: Self-extinguish Pack
Huawei Smart String ESS provides superior safety method: integrating self-extinguish pack (shown below).
The weight of pack is around 1kg and it only needs 15s to extinguish the fire. More importantly, all the
process is inside one pack as a result it can quickly stop the fire from spreading the whole battery system.
The working principle is pluse blowout & gas phase chemical inhibition and the working process is