What Does A Battery Monitor Shunt do? (Why You Need One)

A shunt is a resistor usually coupled together with a battery monitor, that can measure current flow and direction in an electrical circuit. This is useful for knowing how charged your batteries are or if they are being charged or discharged.

It’s standard to install one in any solar system since your batteries health will be negatively impacted if you discharge them too deeply. Typically it’s safe to discharge a LiFePo4 battery down to 15-20% charge without any negative effects. And traditional batteries can be discharged safely down to 50%.

But you would never know your battery’s state of charge unless you use a shunt to monitor it’s capacity.

Installation

A shunt is typically installed on the negative lead of your battery bank. All electrical loads should flow through the shunt, so there should be no other components between it and the battery.

Sizing

Shunts come in different sizes. Since all of your electrical systems amperage will flow through the shunt, it’s important to select the right size shunt for the job. Here are some popular options for Battery Monitoring Shunts used in solar systems.