What Is A Battery Discharger?

In the world of batteries, there are a number of different discharge rates. High-rate applications include power tools and backup battery supplies. Lower-rate applications include household appliances and uninterruptible power supplies. In addition to LiPo batteries, most dischargers support other battery types. HTRC’s battery discharger, for example, supports NiMH, NiCd, LiHV, Pb, and LiFe batteries.

Self-Discharge

The self-discharge function is one of the most critical characteristics for electrochemical energy storage devices. It can be a major contributor to their battery lifetime, and understanding it is vital for improving their electrochemical performances. This video explores various aspects of this process, including the influence of temperature and cell size.

The self-discharging process is a result of the internal chemical reactions that consume the cathode and anode materials of a battery or accumulator. These reactions reduce the battery’s state of charge, causing the open-circuit voltage to decline. The self-discharge rate varies according to the ambient temperature, acid/mass ratio and battery type. In extreme temperatures, such as those experienced in garages and sheds during hot summers, this can be even more pronounced.

Excessive self-discharge can lead to unwanted lithium deposition on the negative electrode, which increases internal resistance and reduces loading capability. The result is reduced performance and premature battery failure, which is why it’s important to conduct regular Battery discharger characteristic tests under controlled conditions.

Capacity Load

The capacity load function is a useful function to understand when designing sealed-lead batteries for various applications. It determines the amount of energy that can be obtained from a battery during its discharging cycle. It takes into consideration the cell or battery temperature and the discharge rate. It also accounts for the effect of the environment on the battery’s performance. The term “standard capacity” refers to the capacity that a relatively new, stabilized cell or battery is capable of delivering when fully discharged to a standard end-of-discharge voltage (EODV). The deliverable capacity varies inversely with discharge rate.

It is important to note that the standard capacity value may be different from the actual capacity value of a battery because of the width (statistical variance) of the battery’s capacity distribution as manufactured. This is particularly noticeable when a battery is used in nonstandard conditions.

Voltage Measurement

Including a sealed-lead battery in a product design typically presents two concerns or questions: 1) How long will the battery be able to supply current and 2) What will the battery’s voltage behavior be over the course of the discharge? The answers to these questions are related to the operating conditions and internal construction of the battery, as well as environmental considerations.

Generally speaking, starved-electrolyte sealed-lead batteries are capable of providing adequate performance in a wide range of temperature environments. The capacity of these batteries varies, however, with the discharge rate.

In low to medium-rate applications, battery voltage remains fairly constant on a plateau until the end of its useful discharge. Once the battery leaves the plateau, the voltage drops rapidly. This is known as the knee of the discharge curve. A battery management system must be able to detect this voltage depression in order to terminate the discharge at the correct time. Otherwise, the battery will experience severe degradation and eventually fail.

Safety

Battery dischargers are a useful tool to help maintain the efficiency and capacity load of batteries on 36V and 48V electric vehicles. However, they are not without their own set of dangers and hazards. These include corrosive sulfuric acid, which can damage surfaces and eat through clothing. It can also cause a spark that could lead to an electrical explosion. It is important to have an established system for maintaining and discharging batteries in an environment that is safe and well-ventilated.

This may involve a combination of electronic loads, power electronics converters and powerful resistors to simulate the discharge behavior of a battery. It is also essential to choose the correct discharge current and monitor the voltage, temperature and performance of a battery during the discharge process. Finally, the equipment should be tested in a controlled environment to ensure consistent conditions. A disconnect circuit should also be included to remove the load from the battery once its discharged.

What’s Next?

The discharge of a battery gradually consumes the residual battery power based on an electrochemical oxidation-reduction reaction. During discharge, electrons flow from the negative electrode to the positive electrode, and positively charged ions move through the electrolyte solution. The discharge voltage remains relatively constant until the battery reaches the flat plateau of its discharge curve. From there, the voltage drops rapidly as lead sulphate is deposited on cell plates.