Single cell of a series of problems caused by inconsistent

Single cell of a series of problems caused by inconsistent


As indicated above, single cell voltage of 3.2V nominal resistance of 10mΩ, capacity of 10Ah, the figure shows the constant current charging phase, in which the internal resistance of the IBM Laptop Battery instead of AC resistance to DC resistance.

In an ideal state, is consistent between two monomers, then through the basic circuit operation can be attached to all of the battery voltage is: 3.2V +0.01 Ω × 2A = 3.22V, so there was no problem.

The actual production of batteries, the actual voltage of each DELL 08K8194 Battery has certain differences, there is a certain gap between the internal resistance in the battery charge power of 10% -90% battery state of charge and open circuit voltage of dc resistance changes in the value of the general is not will not produce any considerable change in the circuit between the battery voltage monomer more balanced. The most obvious changes in various parameters of the battery is charging late (SOC90% above) and the discharge end (SOC less than 10%), the IBM 92P1087 Battery voltage and DC resistance of significant changes will occur, and the different types of batteries are not the same magnitude of changes, which directly the expansion of the difference between the batteries, the voltage distribution is more uneven, and this uneven phenomenon in the early process of using the battery pack is not very clear, with the increase of cycles, the difference in the expansion, for instance, the first expanded to a battery internal resistance 30mΩ, such resistance is not within the relatively large numbers, but the battery voltage is more than other batteries out of 0.04V.

In the actual process of using single IBM 92P1089 Battery capacity gaps on the battery life impact is enormous, because the battery state of charge and internal resistance is most directly related to the process of charging, the other batteries are filled to 90% and a capacity of batteries is less than other batteries some, so that it can achieve the SOC is 95%, I look at a thin single charge and discharge curve, take a look at 90% and 95% in the end how much difference between the voltage:

This is a half-cell of the curve 0.15C, the actual batteries is much more than this to be ugly, especially in the late charge, the IBM 92P1101 Battery capacity of the differences between the minor differences can lead to the battery voltage of the huge differences between two monomers, when the capacity of the smallest full power to charge batteries when the cut-off voltage the resistance is much greater than other batteries (other batteries not fully charged), then we must stop constant current charging, otherwise it will overshoot, there should then be turned to constant voltage float into the state, but as long as there is current through the capacity of the battery voltage must be smaller than the other cells to be, thus can not continue to charge, so the capacity of the IBM 08K8192 Battery only in accordance with the smallest capacity batteries to determine.

There are the smallest capacity batteries discharge when the batteries are always the first to reach than other cut-off voltage, internal resistance than other batteries in turn lead to large voltage drop, creating a vicious circle! Therefore, the performance of the battery than the batteries that the worst is worse.

There are worse things are often the lowest-capacity IBM 08K8193 Battery during charging and discharging batteries would certainly be other burdens are heavy, he has to 0-100% charge and discharge cycles, while the other batteries are relatively light red light is put, we know that the work of high load will shorten the battery life significantly, when the capacity of the smallest battery performance up to a certain critical point, its performance will be showed a sharp decline and then an avalanche-type failure, the entire battery pack batteries due to the failure of the Overall scrap!

Even before assembly in the battery pack is very strictly limited to the capacity of matching IBM 08K8195 Battery and DC resistance, there is a problem is the consistency of charge and discharge curves, the battery is the work of the current series is the same, if the charge-discharge curves of a relatively large differences (including different magnification under the voltage plateau, the curve inflection point, etc.), the two ends of the battery voltage will be very different, although the short-term use of almost no impact, but the cumulative effect of long-term will make a good bad IBM 08K8214 Battery. In particular, under magnification at the same voltage - capacity curve of consistency, also called in a different magnification especially high magnification under the curve must also have a better consistency.

Therefore, to assemble a safe, durable and a good battery pack, the selection of matched pairs of batteries made a very high demand, while the battery pack for security reasons outside the control must be increased access circuit, to detect abnormal voltage of the monomer.

Battery requirement for consistency with the series is proportional to the number of IBM 92P1060 Battery, 36V or 48V battery voltage is easier to achieve a certain degree of consistency, but in electric vehicles, then, how have to have more than 180V DC voltage to drive motor in order to have better motivation and higher current efficiency, so it will require more than 56 cells in series, so much the probability of failure of the battery even higher.

On the one hand the use of high-voltage battery packs require a very high consistency of the battery, on the other manufacturing lithium-ion battery has many complex process steps, resulting in consistency is very difficult to control, this contradiction is constraining the development of lithium-ion battery power important one of the factors - not a long IBM FRU 08K8193 Battery life, rather than single cell itself impossible.