Lithium battery pack is actually composed of a lot of lithium cell plus protection plate, before the combination of the general need to carry out capacity matching, need to test the capacity, internal resistance, voltage and other parameters, to ensure that the consistency of the cell is good, so as to maximize the battery pack, the number of cycles also improve a lot. If two groups of batteries are used in parallel, then whether the cell or the protection plate will have a great difference, the greater the difference, the greater the efficiency loss of the battery!
1. If two battery strings are used in parallel, their voltages are the same and their internal resistances are different, the current provided by the two battery strings will be inconsistent. Similarly, the voltage is different, the internal resistance is the same, also provides the current is not consistent. If they are all different, the current supplied is even more different.
2. In the overcurrent, if the overcurrent protection point of the board is the same, but the current provided is different, there will be a group of protection plate, the other group can discharge normally, but after the overcurrent is over instantly, all the current is provided by the group without protection, so long time will lead to this group of battery attenuation is relatively fast. Of course, there are other conditions that can cause this.
3. In overdischarge, if one group reaches the protection point first or all the current is applied to the others, over time the battery's attenuation will be accelerated, resulting in poorer consistency.
4. If it is also charged, the charging current can not exceed the current of a single series of protection plate. The same port can be directly charged and discharged. The parallel discharge port must be disconnected when the port is charged; otherwise, overcharge protection fails.
5. When the battery strings are connected in parallel, circuits are formed between them. If the pressure difference is large, the inner ring current may be generated, which may damage the protection plate.
Now it is not difficult to understand why the lithium battery can not be connected in series or parallel, but if two different lithium batteries are used together, what should we do? For example, if the lithium battery installed is not enough before, if you want to add lithium battery pack, there will always be a way, we can add a battery switch.
Lithium battery dual power supply automatic switcher, used for automatic switching between two DC power supplies, during the switching power equipment will not break
Main power supply and auxiliary power supply are dc, suitable for all kinds of 12V power supply system.
The maximum current of the switcher is 30 a. it is recommended that the load current be less than 20A.
When the main power supply is larger than 10.8V, the load is powered by the main power supply.
When the main power supply is lower than 10.8V, the load is powered by the auxiliary power supply. After the main power supply is restored, it is automatically switched back to the main power supply.
All switches are seamless, i.e. the time is zero. Power consumption of switcher itself < 1 w.
It is convenient for some equipment to automatically switch to the standby power supply when the main power supply fails. With main power supply voltage monitoring function,
When the main power supply voltage is lower than 10.8V, the automatic switch to the secondary power supply.