Monitoring State of Charge
The Voltage of quality LFP batteries will remain very consistently high and steady throughout the entire discharge phase. This is one of the many major advantages over Lead batteries of all types but it can cause misunderstandings when attempting to monitor State of Charge using old meters. Most old meters only reference Voltage to estimate the remaining Charge of the battery and aren't calibrated for Lithium.
A proper Voltage meter for Lithium batteries can give you a good approximation of State of Charge but it is important to understand the difference between Resting Voltage and Load Voltage.
A shunted battery meter is the most accurate way of monitoring actual LFP battery charge. It basically tracks the amount of Power flowing in and out of the battery to give you a proper % of charge, additionally most will give you real time load draw and charge readings.
An external shunted meter can be used to monitor multiple batteries in one bank.
Our Bluetooth App taps directly in the battery BMS for even more accurate real time readings, including: State of Charge, State of Health, Multiple Temperatures, Voltage, Current Flow (Charge and discharge), Cycles, Errors and Cell Status.
Resting Voltage: Voltage of the battery while not under charge or load. No Current is flowing in or out of the battery. Midrange state of charge, 13.0V - 13.2V
Sag Voltage or Load Voltage: Voltage of the battery while it is actively Powering a load. While Current is flowing out of the battery, the Voltage tends to drop or sag. The higher Current draw (Power output) the more the Voltage will sag.
As the battery drains, the Load Voltage will increasingly sag, and likewise the resting Voltage will trend downward.