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Solar Battery Fire Safety

Solar Batteries & Fire Safety

Storage batteries are an important component of many domestic solar PV installations, storing power generated during the day for use at night. To minimise the risk of batteries becoming a fire hazard,  a new British Standard covering fire safety for home battery storage installations came into force on 31 March 2024.

The standard is – PAS 63100:2024: Electrical installations. Protection against fire of battery energy storage systems (BESS) for use in dwellings.

As an installer, we take fire safety of our client’s installations very seriously. We would always recommend locating storage batteries outside the home and away from rooms used for living. If outdoor placement is not feasible, there are basic requirements for indoor locations housing storage batteries. These include:

  • Ensuring batteries are separated from habitable rooms and escape routes by appropriate fire compartmentation.
  • Providing fire detection for the battery location, linked to a fire alarm system to alert inhabitants of a fire.
  • Making sure that inhabitants’ escape routes are not obstructed.

Part of the new standard is the introduction of warning labels clearly indicating the presence of either battery energy storage system (BESS) or both solar PV and BESS in a building (see left).

Batteries should not be installed in any of the following locations:

  • Rooms intended for sleeping.
  • Routes used as a means of escape that are not defined as protected escape routes, including landings, staircases, and corridors.
  • Corridors, shafts, stairs, or lobbies of protected escape routes.
  • Firefighting lobbies, shafts, or staircases.
  • Storage cupboards, enclosures, or spaces opening into rooms intended for sleeping.
  • Outdoors (ground-mounted or wall-mounted in a suitable enclosure) within 1m of escape routes, doors, windows, or ventilation ports.
  • Voids, roof spaces or lofts.
  • Within 2m of stored flammable materials and fuel storage tanks or cylinders.
  • Cellars or basements that have no access to the outside of the building.

AC or DC Coupled Batteries:

The main difference between AC and DC coupled batteries lies in how they are integrated with a solar power system: AC coupled batteries are connected to the grid via an AC inverter, while DC coupled batteries are connected directly to the solar panels or through a DC inverter, often resulting in more efficient energy storage and conversion.

Round-trip efficiency (%) and energy loss (kWh) if charged from grid electricity:

Charging a solar battery from grid electricity typically results in a round-trip efficiency of around 80-90%, meaning that for every 10 kWh of grid electricity used to charge the battery, 1-2 kWh is lost in the process.

Current cost of additional or replacement battery modules:

Additional batteries can be added to an existing system at any time as long as the model of battery is expandable and there is capacity.

Replacement batteries are available from most installers although developments in technology  may mean that additional works may be required.

The costs of solar batteries depend on make/model and performance of the battery and a quote should be obtained prior to any additional or replacement battery being purchased.

If capable (or not) of running in Island mode (during loss of grid power) and limitations in terms of maximum load in kW:

Most “grid tied” solar systems will not work during a power cut. Islanding mode, as its known, is an additional requirement and requires extra work to the homes existing wiring and split into essential and non-essential loads.

Different brands handle Islanding mode in different ways and the maximum load able to run during a power outage varies.  

Warranties applying to the system and its storage capacity (degradation, number of cycles, energy throughput etc.):

Most batteries are designed to have over 6000 cycles. A cycle is a full charge and discharge, so you can assume this happens once a day.

We only install batteries with a minimum of 10 year warranty and your battery will last around 12-13 years.

How the EESS indicates its current usable capacity or state of health (thus indicating if it is ending its life or the storage capacity is below the warrantied capacity):

All the batteries we install can be monitored via a phone app or website. Here you can see the state of battery charge and if the battery is charging or discharging.

Most batteries also have lights on the front that also indicate the current state of the battery but do not provide the exact level of charge.

End of life, recycling, arrangements in accordance with the Waste Electrical and Electronic Equipment (WEEE, 2012/19/EU) and the Battery Directive (2006/66/EC):

In the UK, the end-of-life recycling and disposal of electronic devices and batteries are governed by the Waste Electrical and Electronic Equipment (WEEE) Directive (2012/19/EU) and the Battery Directive (2006/66/EC). These directives mandate that manufacturers, distributors, and retailers of electronic goods and batteries take responsibility for the collection, treatment, recycling, and safe disposal of these products. The WEEE Directive requires producers to finance the return, treatment, and recycling of electronic waste, ensuring that hazardous substances are safely managed and valuable materials are recovered. Similarly, the Battery Directive mandates that all batteries, including automotive, industrial, and portable, must be collected separately from other waste streams and recycled to minimize environmental impact and conserve resources. Compliance with these directives helps reduce the harmful effects of electronic and battery waste, promoting a circular economy where products and materials are reused, refurbished, or recycled, thus contributing to environmental sustainability and resource efficiency in the UK.

If the EESS can be controlled to respond to time of use electricity tariffs and, if so, how. It shall be highlighted whether this is a manual process (manually setting charge and discharge times) or can be automated (such that charge and discharge times change automatically when tariffs change):

All of the batteries we install can be programmed to charge and discharge as different times in the day depending on tariff rates.

This is a manual process but once set runs automatically.