Using a Battery With EV Charging
A home battery can support EV charging, but how it works depends on system size and configuration.
Using a home battery alongside an EV charger can help reduce reliance on grid electricity, but it is important to understand how the two systems interact.
In most setups, EV charging is a high-power activity. An EV charger typically draws more power than a home battery can supply on its own for extended periods. This means EV charging usually uses a combination of battery power and grid electricity rather than relying solely on the battery.
A battery is most effective when used to supplement EV charging rather than replace the grid entirely. For example, if solar panels are generating electricity during the day, excess solar power can charge the battery. That stored energy can then be used later to support EV charging in the evening, reducing how much electricity is drawn from the grid.
Some smart systems allow charging to be prioritised based on available energy. This can include charging the EV more slowly when only battery power is available, or increasing charging speed when solar or grid power is abundant.
Battery capacity plays a key role. Smaller batteries may only contribute a portion of the energy needed for an EV charge, while larger systems can support longer charging periods. Even when a battery cannot fully charge a vehicle, it can still reduce overall energy costs.
It is also normal for systems to limit battery discharge during EV charging to protect battery health. This ensures the battery remains available for household use and avoids excessive cycling.
In practice, the battery, EV charger, and grid work together. The goal is not to run the car entirely from the battery, but to optimise energy use across the home.