The common off-grid solar controllers in the market are generally suitable for lead-acid batteries and colloidal batteries. With the rise of lithium batteries in recent years, there are more and more solar controllers suitable for lithium batteries.  what is the difference between these two kinds of controllers?

       1.Solar charge controller for lead-acid batteries(AGM,GEL,Sealed)

This kind of solar controller has three-stage charging function, charging parameters are fixed, there are generally 12V and 24V batteries, different manufacturers of solar controllers can be basically universal. It has three charging processes: boost charge, constant voltage charge, and floating charge

       2.Solar charge controller for lithium battery

Lithium batteries are lithium-ion(NiCoMn) batteries, LiFePO4 battery and other types. Generally, multi-string and multi-parallel methods are used to form battery packs. Different combination modes determine that the voltage of the battery is different. The solar controller must modify the charging parameters according to the actual battery pack.

Therefore, there is no uniform specification for the solar charge controller of lithium battery.

For example：  Battery pack with 18650 combination lithium-ion(NiCoMn) batteries：

3 series multi-parallel, rated voltage :3 × 3.7 =11.1V

4 series multi-parallel, rated voltage :4 × 3.7 = 14.8V

       Both combinations are common, so the controller must make corresponding parameter changes for each type of battery pack. Therefore, for the controller of lithium battery, it inecessary to confirm the customer's lithium battery type and battery voltage in order to modify the parameters. The controller is not universal

Lithium batteries and lead-acid batteries are charged differently. The lithium battery is charged in two stages, the boost charge stage, and the constant voltage stage. When the charging current is lower than a certain value, the lithium battery will stop charging, which is different from the controller suitable for lead acid battery.