Charging Controller Series Lithium
FOX Controller for LiFe(Y)PO4 Batteries

The advantages of lithium-based (specifically the LiFe(Y)PO4 chemistry) battery systems include:

• 2-3 times the energy density compared to lead-based systems
• Significantly higher possible cycle count (>=3000 cycles at 80% depth of discharge), about 5-10 times that of lead
• Possible lifespan >= 10 years
• Capacity utilization without significant lifespan loss up to about 90% depth of discharge (DOD)
• High current capability, allowing for charging/discharging over hours
• Flat discharge characteristic, resulting in a high usable voltage level throughout nearly the entire discharge phase
• Low self-discharge
• Environmentally friendly raw materials, significantly lighter than conventional technologies (weight ~1/2 of lead-based technologies)
• High, nearly ideal charge/discharge efficiency, allowing for effective charging even with small charging currents

System Configuration

A LiFeYPO4-based battery system typically consists of 4S (12V) or 8S (24V) series-connected individual cells, which are mechanically and electrically connected into a single unit.

To monitor the battery system, a battery management system (BMS) specifically tailored by the battery supplier to the characteristics of the respective battery type is required. This is essential for safe operation and achieving maximum battery lifespan and must be present. The primary task of the BMS is to monitor each individual cell for compliance with its allowable voltage and temperature limits and to completely disconnect all charging/discharging devices from the battery in case of a fault.

Caution: A single deep discharge of LiFeYPO4 is sufficient to destroy the battery!

Therefore, at least one externally controlled switching device by the battery management system (BMS) must always be installed between the output of the battery system and the (battery) input of the solar charge controller.