There are some advantages and disadvantages of DC Battery Storage. A representative schematic for this kind of solution is shown below;
In this system batteries are connected on the DC side of the Solar PV system, i.e. before the inverter and generation meter. A high voltage battery (to match PV voltage) is used to store the energy when it’s generated for when it’s needed. Advantages of this system include no requirement to inform the DNO about changes to the system connected to the grid if the grid inverter has not been changed. Also there are reduced losses in this type of system as no AC to DC conversion is required.
- There is some (slight) reduction in the PV feed in tariff due to energy used in battery charge/discharge process.
- Not possible to charge the battery from cheap rate electricity (Economy 7).
- Usually no operation in the event of a power cut
- In case of retrofitting DC batteries the existing warranties on solar PV system get invalidated.