All battery types, by definition, store chemical energy, so every battery, if mishandled or overcharged, has the potential for being a hazard by releasing hazardous materials or igniting a fire. Li-ion batteries have been thought to be more volatile due to reported cases of fire and due to their far higher specific energy, combined with a greater sensitivity to being overcharged.
Improperly managed, a Lithium ion battery will reach a “thermal runaway” state more easily as it has a lower cell resistance and higher energy storage capacity than a lead-acid battery. However, much progress has been made over the years, making them safer and much more comparable safety-wise to other commonly used battery types. Chemistry changes and cell packaging improvements have made them more stable. Manufacturing processes are mature and the materials used are more durable. Battery management schemes are well tested and field proven to keep Li-ion batteries from being overcharged or over-heated.
The prolific use of Li-ion batteries in hundreds of millions of portable electronics, smart phones and electric vehicles is positive evidence for their level of safety.
Table 1: Typical performance of Li-ion vs. valve-regulated lead-acid batteries.
| Performance attribute | Li-ion | Valve-regulated lead-acid |
| Specific energy (energy density) | High: 70 to 260 Wh/kg | Low: 15 to 50 Wh/kg |
| Lifespan | 10 to 15 years | 4 to 6 years |
| Number of recharge cycles | >1000 | 200 to 400 |
| Recharge time | 30 to 60 minutes | 6 to 12 hours |
Li-ion battery systems are much more sensitive to how they are charged and discharged, and all include a battery management system (BMS). Microprocessors, sensors, switches and their related circuits make up this system. BMS constantly monitors battery temperature, charge level, and charge rate to protect against short circuits and overcharging. The system is also instrumental in protecting the battery from damage by preventing the voltage from going too low during discharge.
BMS provides the UPS and user with accurate information about battery status, health and available runtime. Although BMSs make Li-ion battery systems much safer, they do come at a cost. They add cost to the solution and drain energy from the batteries, eliminating or greatly reducing the efficiency advantages they offer, compared to lead-acid batteries.
The lithium battery itself is safe, and every point must be strictly controlled in the complex process of manufacturing. From cell selection to battery control system, SCU lithium battery system focuses on safety and reliability. It selects low-heat runaway lithium iron phosphate cells with longer lifespan, and cooperates with active balanced BMS control technology and three-level safety protection measures. While ensuring cycle life and reliability, it has long-lasting stability, larger battery capacity and lower cost per kilowatt-hour, and can be widely used in industrial and commercial energy storage, large-scale energy storage, data centers and other applications.