When we configure off-grid power supply systems, some people may think that since we have a controller to manage the system, the battery cannot be fully discharged anyway, so it doesn't matter if we use fewer batteries to save costs. This is a big mistake! The controller can control charging and discharging, but it generally works based on the lower limit of the battery voltage, which means that when the remaining battery capacity is insufficient, the control system can trigger an alarm or automatically shut down, resulting in long-term deep discharge of the battery pack and system abnormalities in a short period of time. Therefore, when selecting batteries, we must determine the user's actual peak power consumption. If the battery is strictly discharged at around 70%, it can fully meet the user's actual power consumption needs. This is the key factor to ensure that the off-grid system will not experience abnormalities and can operate normally for a long time!