n recent years, increasingly more of products used lithium ion battery do for main power, main is due to lithium ion battery has volume small, energy density high, no memory effect, cycle life high, since discharge rate low advantages; but while lithium ion battery on charging and discharging requirements is high, dang had filled, and had put, and had current and Panasonic Lumix DMC-ZS3 Battery Charger the short circuit, situation occurs Shi, lithium ion battery pressure and heat large increased, easy produced Sparks, and combustion even explosion, so, lithium ion battery no a exception to are plus has had charging and discharging protection circuit. In addition, when a lithium-ion battery charging and discharging when a group, taking into account the various inconsistencies of single cells, balancing measures can be taken to ensure security and stability. This article analyses the importance of balanced treatment, implementation, relationship and protection.
Balanced circuit
Balance is the significance of the use of electronic technologies, lithium-ion battery cell voltage deviation remain within the expected range, thus ensuring each single cell damage does not occur during normal use. If no balance control, with the increase of charge and discharge cycles, differentiation of the single battery voltage gradually, life will be greatly reduced.
Under normal circumstances, rechargeable lithium-ion battery cell voltage deviation in 50mV range is perfectly acceptable. Single cell voltage deviation caused single cells are the main reasons on the one hand there are differences, on the other hand electronic circuit for measurement of consumption as a result of.
There are many ways to balance, such as switched-capacitor balance method, method of a buck converter, the average voltage balancing method, not going to repeat here. Average Nikon Coolpix S640 Battery Charger voltage balancing method is used in this article, schematic diagram shown in Figure 1, figure of only a single cell is given in balanced circuit, every other single cells equipped with the same balanced circuit, amplifier by the single battery supply.
This idea of balance control circuit is: compared to the single battery voltage and average voltage of single cell, control power switch the battery voltage is higher than the average voltage of single cell separation. Therefore, all single cell voltage equalization circuit under the trend of average battery voltage.
Looks at the beginning of this circuit is open-loop control, in fact, due to the role of the internal resistance of the battery, balanced characteristics of closed-loop circuits with negative feedback. Balanced circuit in order to prevent battery discharge while you work, lower power switch Zener diodes in series, so that when the batteries to discharge, battery voltage the lower the loss of shunt circuit.
Protection and balanced relationship
Set current voltage of each battery for Vbati (i=1-7), maximum voltage of Vmaxi (i=l-7), the minimum JVC BN-VF823 Battery Charger voltage Vmini (i=1-7), always current-voltage Vall, total maximum voltage for the Vmax, total minimum voltage of Vmin. You have:
Total voltage and maximum unit voltage changes are closely related. So, our focus is placed on the rate of voltage change on the battery, select the seven relatively high match battery, convergence for all battery change, avoid as much as possible because a battery’s voltage rate of change caused by too large overall problem