When we need to connect batteries in parallel?
When you need to double the battery capacity or ampere hours (Ah) rating according to your system needs while maintain the same level of voltages.
If you have two 12V, 200Ah hour batteries and you need 12V system for installation. Simply, connect both of the batteries in parallel where the overall battery capacity would be 400Ah and the same voltage level i.e. 12V.
Keep in mind that battery discharge quickly in parallel as compared to series batteries connection. You can do it with any number of batteries i.e. to get the same level of voltage while increase the battery capacity in ampere hours in parallel batteries connection.
Charging Lithium Battery in Parallel
When lithium batteries are charged in parallel, each lithium battery should be charged in a balanced manner, otherwise the performance and life of the entire set of lithium batteries will be affected during use. Commonly used balanced charging technologies are: constant shunt resistor balanced charging, on-off shunt resistor balanced charging, average battery voltage balanced charging, switching capacitor balanced charging, step-down converter balanced charging, inductance balanced charging, etc.
These Aspects you need to mind when you charge Lithium Battery in Parallel
1.) One Lithium battery with protection plates and one lithium battery without protection plates cannot be charged in parallel. Batteries without protective plates are easily damaged by overcharging.
2.) Batteries that are charged in parallel usually need to remove the protection board that comes with the battery and use a unified battery protection board.
3.) If the battery charged in parallel does not have a lithium battery protection board, the charging voltage must be limited to 4.2V, and a 5V charger cannot be used.
4.) After the lithium batteries are connected in parallel, there will be a charging protection chip to charge and protect the lithium batteries. When making parallel lithium batteries, lithium battery manufacturers have fully considered the characteristics of the changes after the lithium batteries are connected in parallel, and the current design and battery selection are also carried out in accordance with the above requirements. Therefore, users need to follow the instructions for parallel lithium batteries to charge step by step to avoid damage that incorrect charging may cause to the battery.
When We Need to Connect Batteries in Series-Parallel?
When you need to double the battery capacity or ampere hours (Ah) rating as well as batteries voltages according to your system needs.
For example, If you have six batteries each of 12V, 200Ah hour and you need 600Ah capacity and 24V system for installation. Now you have two sets of three batteries, simply, connect two sets of three batteries in series and then connect the two set in parallel (as shown in fig above) where the overall battery capacity would be 600Ah and level of voltages would be 24V.
You can do it with any number of batteries i.e. to get different level of voltages as well as increase the battery capacity in ampere hours in series-parallel connection of batteries.