BOS smart battery management
The heart of the hybrid system explained by experts
Lithium for cycling and Lead-acid for basic load
The principle of the hybrid system considers the low-cost lead-acid battery as long-term storage and backup, while the lithium battery handles the daily cycles. Through this combination it is possible to counteract typical shortcomings of the lead technology with the lithium battery. For this purpose, the BOS smart battery management system monitors the applied voltages and the behavior of the lead-acid battery, it adapts the behavior of the lithium battery to achieve an improved performance and lifetime of the overall system.
During the charging process, the lead-acid battery reaches constant voltage charge and the charge current reduces. The smart battery system detects this and the LE300 absorbs the available energy that is not taken by the lead acid battery. As a result, both batteries are charged at maximum available charge current, until they are full. Especially with solar power, the full potential of the sun can be realized in every moment, while the lead acid battery gets many charging hours to reach 100% every day.
When not using a lead acid battery during winter, it must be connected to a charger. Also for this use case, the LE300 lithium battery keeps the lead-acid battery fully charged for several months, with a voltage around 13V that allows to maintain the lead acid battery healthy, without being connected to a landline.
In daily use, the lithium battery powers the loads. This way, the lead acid battery is kept full and the lithium battery makes the daily cycles. The battery management system, however, manages to cover large load peaks by both batteries in parallel. Therefore, the BOS hybrid technology can supply even the largest load peaks, without any limits or unexpected system shutdowns. In contrast, with pure lithium systems, huge load peaks can be limited cause issues once by the BMS tries to protect the battery cells, leading to error messages or unexpected system shutdown.
For extended power usage, or on bad weather days, the lead-acid battery with its cheap large storage capacity remains as a backup. This way, both batteries can do what they are designed for – a downsized li battery for the daily cycles, and a lead acid backup, always kept ready for larger amounts of energy needed.
In existing systems, used lead acid batteries can continue to be used and does not need to be replaced. Any capacity can be added to existing batteries. This way the lead-acid battery can be used in a second life, and does not become wasted. An important step to meet the responsibility towards our planet and the environment.
Safety is always first
Engineered in Germany, the BOS LE300 has an inbuilt Battery Management System, with has several effective protection mechanisms to prevent risks or damages by any external influence. Thanks to the simple plug and play approach with the multiple protections built in, you don’t need to be a battery expert to use the LE300 safely. The smart battery management system monitors the applied voltages and the behavior of the lead-acid battery, it adapts the behavior of the lithium battery to achieve an improved performance and lifetime of the overall system.
Each LE300 module has a built-in electronic protection mechanism against short circuits. In a redundant manner, each module is additionally equipped with its own 20-amp fuse, which protects the LE300 in the event of a short circuit with fully redundant protection features.
The LE300 has several temperature sensors that ensure that the lithium batteries are not operated at harmful temperatures. The integrated cell heating allows to charge the battery in extreme temperatures. In case extremely high or low temperatures are detected, the LE300 will reduce its maximum power, and outside the operation range it will shut down to protect the health of the lithium cells.
The protection against wrong polarity connection ensures that the LE300 will not be damaged if the plus and minus pole is accidentally reversed. The LE300 will also check for appropriate lead acid battery voltage, so there is no voltage on the LE300 plug until appropriate connection is established.
Overvoltage protection elements are installed as important components that ensure that dangerous overvoltages are grounded in fractions of a second, preventing the destructive high voltage from reaching the LE300 battery cells and BMS electronics.
Overcurrent protection in the LE is a protective function in the LE300 BMS, to limit the current flow, which protects the circuit and enables to power big loads from LE300 and lead acid battery in parallel, working together for ideal performance.
The overcharge protection circuit of the BMS protects the battery from overcharging. When a battery is charged, the voltage between the battery’s anode and cathode rises. When fully charged, the terminal voltage reaches a peak value indicating a full charge. Charging a battery cell beyond its full value will result in permanent or temporary damage to the battery, so the BMS tracks every single cell voltage, and protects the battery effectively.
The BMS protects against deep discharge of the lithium cells. It shuts down before one battery cellit discharges completely, so there is always a small amount of energy saved to keep the electronics active. A highly efficient sleep mode will allow to recognize charging voltages. After some weeks in completely empty mode the LE300 will protect itself with a deep sleep mode, that consumes almost no energy but requires to press the button to wake up the unit for the next charging.
We value the integration of all possible safety features. The in-house research and development department in Germany develops and tests all components in detail. This is the key to guaranteeing higher quality and safety than purely imported products tend to bring. Experience the outstanding performance and quality of BOS products for yourself.