Disclaimer: 40A controller is not suitable for lithium batteries

Our solar charge controller is definitely born to guarantee full control of electrical flows and protection. It features PWM 3-stage charging process--bulk, absorption and float stage-- for a rapid, intelligent and safe charging to batteries including Lead acid, AGM And Gel. Over temperature protection, over current, over power, low voltage, over voltage are integrated to safeguard your solar panel. And overcharging, over-discharging, short-circuit protection are also integrated to offer an extra layer of protection. Double dual USB ports are designed to offer more convenience in charging electronic devices. Last but not the least, it features a large screen LCD display which is controlled by intelligent chip with low power consumption and long life. Providing you a real-time view of the input, output and battery conditions.

Application: Suitable for farm solar power system, solar street light, solar billboards, outdoor camping solar system, ship solar system, home applications etc.

Why do you need a solar charge controller?

A solar charge controller (frequently called regulator) is similar to a regular battery charger, i.e. it regulates the current flowing from the solar panel into the battery bank to avoid overcharging the batteries. (If you don't need to understand the why's, scroll to the end for a simple flow chart). As with a regular quality battery charger, various battery types are accommodated, the absorption voltage, float voltage can be selectable and sometimes the time periods and/or the tail current are also selectable. They are especially suited for lithium-iron-phosphate batteries as once fully charged the controller then stays at the set float or holding voltage of around 13.6V (3.4V per cell) for the remainder of the day.

The most common charge profile is the same basic sequence used on a quality mains charger, i.e. bulk mode > absorption mode > float mode. Entry into bulk charge mode occurs at:

sunrise in the morning
if the battery voltage droops below a defined voltage for more than a set time period, e.g. 5 seconds (re-entry)
This re-entry into bulk mode works well with lead-acid batteries as the voltage drop and droop is worse than it is for lithium based batteries which maintain a higher more stable voltage throughout the majority of the discharge cycle.

Lithium batteries (LiFePO4) do not benefit from re-entry into bulk mode during the day as the internal impedance of the lithium batteries increases at high (and low) states of charge as indicated by the orange vertical lines in the chart below and it is only necessary to occasionally balance the cells which can only be done around the absorption voltage. A related reason is to avoid the rapid and large variation in voltage that will occur in these regions as large loads are switched on and off.