Why Battery Management Systems Are Vital In Lithium Iron Phosphate Batteries

Overview

Lithium iron phosphate batteries pack a great deal of electricity and worth to a little bundle. The chemistry of those batteries is a large portion of the exceptional performance. However, all respectable commercial ion batteries additionally incorporate another significant component together with the battery cells : a carefully constructed digital battery management system (BMS). A well-designed battery control system shields, and tracks a lithium ion battery to maximize performance, optimize life, and ensure safe operation on a broad assortment of conditions.

In RELiON, our lithium iron Molicell 18650 batteries incorporate an external or internal BMS. Let us have a peek at the way the RELiON BMS protects and optimizes the performance of a lithium iron phosphate battery.

Molicell 18650

Over and Under Voltage

Lithium iron phosphate cells function safely over a range of voltages, typically from 2.0V to 4.2V. Some lithium chemistries lead to cells which are highly sensitive to overvoltage, but LiFePO4 cells are somewhat more tolerant. However, significant overvoltage for a protracted period during charging may lead to plating of metallic ion on the battery’s anode which permanently interrupts performance. Additionally, the cathode substance may oxidize, be secure, and create carbon dioxide that might result in a buildup of stress in the mobile. All RELiON battery control methods restrict every cell and the battery itself into some maximum voltage. The BMS from the RELiON RB100 LiFePO4 battery, as an instance, protects every cell in the battery and also restricts the voltage from the battery to 15.6V.

Undervoltage during battery release can be an issue because releasing a LiFePO4 cellphone below about 2.0V might create a breakdown of the electrode materials. Lithium batteries have a recommended minimum operational voltage. From the RELiON RB100, as an instance, the minimal recommended voltage is 11V. The BMS functions as a failsafe to detach the battery in the circuit when any mobile falls below 2.0V.

Overcurrent and Short Circuit Protection

Each battery has a maximum specified current for secure performance. When a load is put on the battery that brings a greater present, it could lead to overheating the battery. While it’s very important to utilize the battery at a means to maintain the current draw beneath the most specification, the BMS again functions as a backstop against overcurrent requirements and disconnects the battery out of functioning.

Again, utilizing the RB100 as an instance, the maximum constant discharge current is defined at 100A, the peak discharge current is 200A, and also the BMS disconnects the battery in the circuit in the event the load attracts approximately 280A.

A brief circuit of the battery life has become the most severe kind of overcurrent condition. It commonly occurs when the electrodes are inadvertently connected with a bit of metal. The BMS must immediately discover a brief circuit condition ahead of the abrupt and enormous current draw overheats the battery also causes catastrophic harm. From the RB100, the battery shuts down in 200-600 microseconds of an external short circuit, and then resumes normal operation when the brief circuit condition is removed.

Over Temperature

Unlike lithium ion cobalt ion batteries, lithium ion phosphate batteries function effectively and securely at temperatures around 60oC or longer. However, at greater operating and storage temperatures, much like all batteries, the electrode materials will start to degrade. The BMS of a lithium ion battery employs embedded thermistors to actively track the temperature during performance, and it’ll disconnect the battery in the circuit in a predetermined temperature. At the illustration of this RELiON RB100, the BMS disconnects the battery 80oC (176oF) and reconnects the battery in 50oC (122oF).

Molicell 18650

Cell Imbalance

Lithium-ion batteries have a significant gap from lead-acid batteries as soon as it comes to balancing the voltage in every single cell during charging. Due to small differences in manufacturing or working requirements, each cell in a battery costs in a slightly different pace. In a lead-acid battery, even if a single mobile charges quicker and reaches its entire voltage, the normal low end of charge present, together with the surplus charge-return, will guarantee the other tissues get completely charged. In a feeling, the cells at a lead-acid battery are self-equalizing through charge.

This isn’t true with batteries. Every time a ion mobile is fully charged, its voltage starts to grow further which may cause electrode damage. In the event the cost of the full battery is ceased when only 1 cell is fully charged, the rest of the cells don’t reach whole charge and the battery will function under summit capacity. A well-designed BMS will guarantee each mobile securely and completely charges prior to the charging process is complete.

Summary

Lithium iron phosphate batteries comprise of more than simply individual cells connected together. They also incorporate a battery management system (BMS) that, although not generally visible to the end user, which makes certain every cell in the battery stays within safe limits. All of RELiON lithium iron phosphate batteries contain an external or internal BMS to safeguard, control, and track the battery to guarantee safety and maximum life within the entire selection of working conditions.