How does smart solar batteries backup?


With the promotion and application of renewable energy, solar energy is used in all walks of life. Next, let’s popularize the knowledge of smart solar batteries.

The Myth of Whole-Home Battery Backup

The combination of a battery backup system and solar energy has been hailed as the best solution for California’s public safety outages—not to mention our ancient power grid.

These systems are not only ideal for powering homes during power outages, but they also help reduce electricity costs and provide grid support services when required by local utilities. For emission and cost reasons, traditional gas or diesel generators are not an option.

Therefore, it is not surprising that the demand for these systems exceeds the equipment supply and the availability of qualified installation labor.

Limits to whole-home battery backup

But there is a problem. We like to believe in the myth that the entire family backs up, or believe that our 21st century lifestyle will continue unabated, despite the fire hell or the high water level. The reality is different: a typical backup battery system works best when it is designed to allocate battery capacity and minimize the use of major electrical appliances.

In fact, the myth often originates from: Whole-house battery systems are indeed suitable for off-grid applications. It is estimated that there are 180,000 such houses in the United States.

But these houses are designed for off-grid living: they are usually smaller and well insulated; they use combustion heating with propane backup; they combine active and passive solar thermal systems; and they don’t have power-hungry air conditioning systems and level 2 electric car charging Device or swimming pool.

There are two basic engineering limitations that make it impractical to run an entire house on battery power alone. First, the energy capacity of a typical lithium-ion battery system is not enough to power the entire house through a power outage at night. Secondly, the power of the backup battery inverter is not enough to start and run many large electrical appliances.

Of course, multiple batteries and inverters can solve these energy and power constraints. However, the cost of inverters of more than 20 kilowatts and batteries of more than 40 kilowatt hours are high for a typical homeowner.

A more practical approach is to design a battery backup system that only supplies power to critical loads: no air conditioners, 240-volt electric car chargers, or large appliances such as electric stoves. Instead, there are only four to eight smaller circuits in the house for cooling, lighting, entertainment, communications, and convenience outlets.

Our current houses consume a lot of electricity, and because of the large number of plug-in devices, newer houses usually use more.

High-power electrical appliances are the most challenging for the family backup system. The large central air conditioner consumes 5,000 watts of electricity, the electric vehicle charger is 7,000 watts, the electric furnace is 10,000 watts, and the water pump is 2,200 watts.

Battery energy limits

So how long does a typical solar and battery system operate at night while operating these larger appliances? Answer: not very long at all.

The math is simple. If the energy capacity of the battery at night drops to 2.5 kWh (a typical situation is to use the battery at night to maximize self-consumption), the battery energy is only enough to run the pool pump for 60 minutes, which is a central problem. AC for 30 minutes, EV charger for 20 minutes or electric stove for 15 minutes.

With any of these appliances running-only after a relatively short interval of automatic family backup-the battery will quickly run out and unable to power critical loads. In lyrical words: no lights. no phone. There are no electric cars. No luxury at all. Like Robinson Crusoe, as primitive as possible.

One possible solution is to manually turn off large electrical loads during power outages. Unfortunately, many power outages occur when no one is at home during the day or when people are sleeping at night. Customers who try to manually offload the load often end up disappointed with their backup system.

Another solution (if the homeowner’s budget and wall space allow it) is to add a second battery-effectively doubling the duration of the energy storage.

In the past few months, we have worked with customers who have a series of good and bad battery backup experiences. During the first power outage in our area, at around 10:30 in the evening, a customer using a continuous positive airway pressure (CPAP) machine ran out of his battery at around 2 in the morning (he started snoring, he His wife let him continue to sleep) on the sofa). Another customer used a backup system to power a sub-panel in his home. He did not realize that a power failure had occurred until the battery was exhausted.

The solution provided for these two customers is to remove some of the discretionary circuits from their spare sub-panels so that the battery can be used overnight.

Inverter power limits

The maximum output power (kw) of the battery inverter is the second reason for the backup myth of the entire family.

Most backup battery inverters are designed for 200 amps of household electricity service, which means that the maximum AC output when connected to the grid is 7,600 watts. When powered by batteries (with a limited peak discharge rate), these inverters can typically provide 5,000 watts of steady-state power or 6,000 watts of peak power (approximately 25 amps).

However, the instantaneous start-up surge current requirements of AC motors or pump motors are usually two to three times the normal current consumption-which means that the inverter will not switch to standby mode at all. Even if the battery is fully charged on a sunny day, the AC and swimming pool pumps will not start, and any critical loads will not receive power.

Designing solar-coupled battery backup systems

Regardless of these energy, power, and financial constraints, well-designed solar and backup systems can provide power almost indefinitely. Three design elements are essential.

First of all, the energy capacity of the battery (kWh) and the inverter output (kW) should match the household needs when the battery is partially discharged at night. Second, the number of backup circuits should be strictly limited to prevent too many small devices or any large electrical appliances from supplying power. Third, even on a cloudy winter day, the size of the solar system should be large enough to partially charge the battery.

The upcoming smart home power system technology will address these practical limitations by automatically unloading loads during power outages. At the 2019 International Solar Energy Exhibition, the company demonstrated smart appliance control devices and circuit breakers that can automatically disable large appliances. It also demonstrated smart electric panel technology, which can automatically manage all circuits in the house.

By the end of 2019, there will be more than 10,000 homes and businesses in California equipped with combined solar and battery backup systems. As these systems become cheaper (through reductions in equipment costs and incentives), they will become the most expedient and most effective way for people to adapt to the new normal of public safety outages.


As the most abundant renewable energy source, solar energy is inexhaustible and inexhaustible. As long as there is sunlight, solar cells can store electricity.For other types of batteries, solar energy is the most environmentally friendly.

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