Battery quick charging method
In order to maximize the speed of the chemical reaction of the battery,
shorten the time for the battery to reach a full charge state, and at the same
time ensure that the polarization phenomenon of the positive and negative plates
of the battery is minimized or lightened, and improve the efficiency of the
battery, fast charging technology has been rapidly developed in recent years.
develop. Several popular fast charging methods are designed around the optimal
charging curve, with the purpose of making the charging curve as close to the
optimal charging curve as possible. The conventional charging method adopts a
low-current slow charging method. It takes more than 70H to initially charge a
new battery, and more than 10H for ordinary charging. If the charging time is
too long, it will not only prolong the charging detection time and cause a waste
of electric energy, but also limit the number of battery recycling times and
increase the maintenance workload. The use of fast charging method can shorten
the charging time of the battery, increase the charging rate, save energy, and
increase the number of battery recycling times, which has great practical
significance.
(1) Battery fast charging technology
In the mid-1960s, American scientist Maas did a lot of research on the gas
evolution of the battery charging process, and proposed an acceptable charging
current curve for the battery based on the lowest gas evolution rate. During the
charging process, only the charging current is required, so the charging time is
greatly extended. In the later stage of charging, the charging current is
greater than the acceptable current of the battery, so a large number of bubbles
are generated in the battery. However, if the actual charging current can always
be equal to or close to the acceptable charging current of the battery during
the entire charging process, the charging speed can be greatly accelerated, and
the gas evolution rate can also be controlled in a very low range. This is the
basic theoretical basis of fast charging. However, during the charging process,
the polarization voltage generated in the battery will hinder its own charging
and significantly increase the gas evolution rate and temperature rise.
Therefore, the polarization voltage is an important factor affecting the
charging speed. It can be seen that in order to achieve fast charging, we must
try to eliminate the impact of polarization voltage on battery charging. It can
be inferred from the formation mechanism of polarization voltage that the
magnitude of polarization voltage changes closely with the change of charging
current. When charging is stopped, the resistance polarization disappears, and
the concentration polarization discharge channel and electrochemical scheme also
gradually weaken. If a discharge channel is provided for the battery to
discharge in the opposite direction, the concentration polarization and
electrochemistry will disappear quickly, and the temperature inside the battery
will decrease due to discharge. Therefore, suspending charging during the
battery charging process and appropriately adding discharge pulses can quickly
and effectively eliminate various polarization voltages, thereby increasing the
charging speed. At present, the fast charging methods that everyone agrees with
are pulse charging and pulse discharge depolarization methods.
(2) Technical approaches to achieve fast charging
1. Improve battery design and reduce ohmic internal resistance. If the
battery uses a copper drawn mesh negative electrode grid, the grid resistance
will be significantly reduced. This not only helps to improve the utilization
rate of active materials and the specific power of the battery, but also
improves the fast charging performance of the battery. 2. Increase the
occurrence time of reactive ion diffusion current, that is, extend the time for
the battery voltage to reach the gas evolution voltage, thereby allowing the
charging current to be increased, the plate thickness to be reduced, the active
material porosity to be increased, and the grid active material contact area to
be increased. These measures are beneficial to the diffusion of reactants and
products, reduce concentration polarization, increase the allowable charging
current, and achieve fast charging. However, considering the life of the
battery, the plates cannot be made too thin. 3. Reform the battery charging
method. The theory of the pulse fast charging method is basically to superimpose
negative pulses of a certain frequency and height or a short-term charging stop
in the charging current, so that the lead ions participating in the reaction can
be generated and increase their concentration, and the generated hydrogen ions
and sulfate radicals can be generated. The ions have time to move away from the
vicinity of the electrode, and the overall effect is an effective measure to
reduce the concentration difference. The battery voltage rises slowly, allowing
the battery to charge more electricity. The intelligent charging device
currently developed is designed with these situations in mind. 4. The impact of
fast charging on battery life. The impact of high-current fast charging on
battery life is still under discussion. There are also different views in the
industry. First of all, the service life of batteries is not consistent, and
their cycle life can even vary by a factor of 1. Furthermore, during the
long-term life test process, it is difficult to ensure that the test conditions
of each batch of batteries are completely consistent. Although it is generally
believed that high-current fast charging does not adversely affect the life of
valve-regulated sealed lead-acid batteries.
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