(Based on standard depth of discharge for both Lithium (80%) and AGM (50%).
Another advantage is the weight and physical dimensions of lithium units, when compared to AGM style. Lithium batteries are more compact, and much lighter. Lithium are also designed with much newer and more advanced technology, making them the better option for longevity. Also, you do not have to ensure lithium sit upright like AGM, as there is no liquid in them!
A PWM controller is essentially a switch that connects a solar array to a battery, so the voltage of the array will be pulled down to near that of the battery.
A MPPT controller will adjust its input voltage to harvest maximum power from the solar panels, and then transform this power to provide the varying voltage requirement of the battery plus load.
The PWM is a good low-cost option for:
Where the efficiency of the system is not critical
When solar cell temperature is moderate to high (45°C to 75°C).
The MPPT controller is best for:
Larger, higher power systems
When the array voltage is substantially higher than the battery voltage
When the solar cell temperature is low (below 45°C) or very high (above 75°C)
Ideally you will need a battery charger with a lithium profile to charge a lithium battery.
Some battery chargers without a lithium profile, in theory, could be used to charge a lithium battery but they will never get the battery to 100%. There are also other technical risks associated. Our advice is to not do it. Our advice is to choose a battery charger with a lithium profile.