dc power system

As a core component of the DC power system, the battery plays a key role in reserving power, coping with abnormal and special working conditions of the power grid, and maintaining the normal operation of the system, and is the big heart of the normal operation of the power system. However, relaxing the daily maintenance and management of the battery will reduce and damage the early capacity of the battery, resulting in a larger internal resistance of the battery and shortening the normal service life of the battery.
Here is an analysis of the main factors affecting the internal resistance of the battery:

01
Time of use of the battery

If the battery is used for a longer period of time, the electrolyte will lose water, the corrosion of the pole plate and the connection strip, the sulphation of the pole plate, the deformation of the pole plate, and the shedding of the active substance, etc., which will lead to the reduction of the battery capacity and the increase of the battery internal resistance.

02
Battery charge

The depth of the electrolyte injected into the battery, the thickness of the reactive substance on the electrode surface, the porosity of the electrode surface, etc. will cause a large difference in the charge of the battery and thus a large difference in the internal resistance.

03
Ambient temperature

Changes in ambient temperature, e.g. an increase in temperature, will result in faster diffusion of reaction substances, easier charge transfer, electrode kinetic processes and substance transfer, which will result in a relative decrease in the internal resistance of the battery. Conversely, it increases.

04
Model of the battery

Different manufacturers, different types and models of batteries, due to the different material formulations of electrodes, electrolytes and diaphragm, different battery structures and different assembly processes, thus making differences in the internal resistance of the battery.

05
Measuring time and measuring current size

When using a larger measuring current, the polarisation is different for different measuring currents and measuring times, as the establishment and stabilization of the polarization is a changing process when the measuring signal is applied and switched off, making the battery internal resistance measurement results not objective. Therefore, if you want to have objectivity, you should try to use a smaller signal current for internal resistance measurement. According to the experiment, the measurement current should be less than or equal to 0.05C10, (where C10 is the capacity of the battery at 10 hours discharge rate.)

06
Effect of overcharging

Under the long-term overcharging condition, the positive electrode is consumed due to an oxygen precipitation reaction, water is consumed and h+ increases, which leads to increased acidity near the positive electrode and accelerated corrosion of the plate grid, which makes the plate grid thinner and accelerates the corrosion of the battery and reduces the battery capacity; at the same time, the battery will be in danger of drying up due to increased water loss, which affects the battery life.

07
Impact of over-discharge

Battery over-discharge mainly occurs after the AC power failure, the battery for a long time for the load power supply. When the battery is over-discharged to a low or even zero voltage, this can lead to a large amount of lead sulphate being adsorbed onto the cathode surface of the battery, causing “sulphation” at the cathode of the battery.
Lead sulphate is an insulator and its formation will have a great negative impact on the charging and discharging performance of the battery, therefore the more sulphate formed on the cathode, the greater the internal resistance of the battery, the worse the charging and discharging performance of the battery and the shorter the service life of the battery.