Low self-discharge rate
main content
In the field of power batteries, the self-discharge rate is a key indicator for measuring the energy retention capacity of batteries in an idle state. Lithium iron phosphate (LiFePO₄) start-stop batteries, with their outstanding performance of a monthly self-discharge rate of less than 3%, have completely solved the problem of long-term parking power loss caused by the high self-discharge rate (5% to 15%) of traditional lead-acid batteries (AGM/EFB), making them an ideal choice for backup power sources, seasonal equipment, and vehicles that are parked for a long time. The following is a deep analysis of its low self-discharge characteristics from three dimensions: technical principles, measured data and scene applications.
I. Technical Principle: Material Stability and System Synergy
The olivine-type crystal structure of lithium iron phosphate cathode material (with a PO bond energy of 800kJ/mol) hardly undergoes side reactions with the electrolyte in the static state, fundamentally suppressing self-discharge. In contrast, PbO₂ and PbSO₄ in lead-acid batteries continuously self-decompose in sulfuric acid electrolyte, resulting in an average daily self-discharge rate as high as 0.2% to 0.5%.
2. Optimization of the electrolyte system
The electrolyte formula with lithium fluoride salt (LiPF₆) and low viscosity carbonate solvent has an oxidation potential >4.5V and an ionic conductivity attenuation rate <0.1%/ month at room temperature. The sulfuric acid electrolyte in lead-acid batteries is volatile and decomposes easily, accelerating self-discharge.
3. BMS sleep Management
The built-in BMS of lithium batteries reduces self-discharge through the following mechanisms:
Sleep mode: Automatically switches to A low-power state (working current <10μA) when idle. For example, the self-discharge rate of the ENOV Bluetooth series (EN12BT180B) can be further reduced to 1.5% per month during sleep mode.
Battery lock: When the SOC (remaining battery) drops to 50%, the BMS cuts off unnecessary circuits to prevent continuous energy loss.
Ii. Measured Data: Scientific Verification of Long-term Energy Storage
According to the ENOV product specification (STORAGE AND SHIPMENT REQUIREMENT) and industry test standards, the comparison of the self-discharge performance of the two types of batteries is as follows:
| Test conditions | Lithium iron phosphate battery | AGM/EFB lead-acid battery |
|---|---|---|
|
The monthly self-discharge rate at 25°C |
≤3% |
5%/15% |
|
Monthly self-discharge rate at high temperature (40°C) |
≤5% (BMS temperature control intervention) |
≥20% (electrolyte accelerated decomposition) |
|
6-month capacity retention rate |
≥85% |
≤50% (regular recharging is required) |
|
One-year capacity retention rate |
≥70% (initial SOC value 80%) |
≤30% (possible deep battery depletion damage) |
Typical case:
The EN12ST180B model was left to stand in an environment of 25°C for 12 months. Its capacity decreased from 18Ah to 15.3Ah (attenuation rate 15%), but it could still output a cold start current (CCA) of 540A.
Under the same conditions, the capacity of the traditional YTX30LBS lead-acid battery drops from 18Ah to 5.4Ah (with a attenuation rate of 70%), completely losing its starting ability.
Iii. Application Scenarios: Essential fields with low self-discharge
1. Seasonal vehicles and equipment
Motorcycles/snowmobiles: In the Nordic region during winter, the vehicle can be parked for 46 months, and the lithium battery can maintain its starting ability without external charging.
Yacht/RV: The EN12BT060B model was placed in a dock environment with a humidity of 85% for half a year, and its capacity retention rate was over 80%.
2. Emergency backup power supply
Vehicle-mounted emergency kit: Lithium batteries can maintain effective standby for more than 3 years (such as the ENOV Reboot series), and lead-acid batteries need to be recharged every 3 months.
Medical equipment: Defibrillators and other devices rely on the long-lasting energy storage of lithium batteries to prevent power loss at critical moments.
3. Logistics and rental vehicles
During the off-peak idle period of shared cars and rental motorcycles, the frequency of lithium battery maintenance and recharging is reduced, lowering labor costs by more than 50%.
Iv. Comparison of Mechanisms with Traditional Batteries
| Self-discharge causes | Lithium iron phosphate battery | Lithium iron phosphate battery |
|---|---|---|
|
The chemical side reaction |
almost no active substance decomposition |
PbO₂ + H₂SO₄ → PbSO₄ + H₂O |
|
Electrolyte stability |
non-volatile and non-corrosive |
The evaporation of sulfuric acid accelerates the sulfidation of the plates |
|
External environment effect |
BMS’s automatic compensation for temperature fluctuations |
High temperature/high humidity environments accelerate self-discharge |
|
Maintenance requirements |
Completely maintenance-free |
Regular liquid and power replenishment |
Conclusion
The low self-discharge rate of lithium iron phosphate start-stop batteries is the result of the combined effect of the chemical inertness of the material, the stability of the electrolyte and the intelligent BMS. From the snowy plains of Northern Europe to tropical docks, from emergency medical care to shared mobility, its "long-lasting preservation" feature is reshaping the reliability standards of energy storage. For users who pursue low operation and maintenance costs and high equipment availability, lithium batteries are not only a choice for technological upgrades but also an inevitable option to deal with long-term idle scenarios. With the growth of Internet of Things (iot) devices and intermittent power demand, a low self-discharge rate will become a core competitive dimension for energy storage technology.
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START-STOP LITHIUM battery
Enov start-stop battery is designed to provide excellent performance for high-demand start-stop vaehicles. It adopts the third-generation intelligent lithium platform architecture to achieve technological breakthroughs in core indicators such as cycle life, environmental adaptability and energy density. Compared with the traditional lead-acid battery system, the energy efficiency is increased by 210%, the cycle life is extended by 8-10 times, and the monthly self-discharge rate is controlled within 3%. Enov's unique low-temperature battery technology makes a breakthrough in achieving stable output in the whole climate domain from -30℃ to 65℃, maintaining more than 90% of the effective capacity release under extremely cold conditions (-30℃), and maintaining 90% of the capacity in high temperature environments (65℃).
The start-stop battery series products cover the mainstream voltage platform of 12V/24V/48V, and support flexible configuration of LFP (lithium iron phosphate) and NCM (lithium nickel cobalt manganese oxide) dual-material system. All models adopt modular design to support customization of different model specifications. Enuo engineering and technical team to provide full cycle technical service support, if you need, please contact us.
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