Home Solar Battery: 3 Technical Details for Choosing the Right Battery
Publish Time: 2022-10-08 Origin: Site
Tesla, Huawei, LG, Sonnen, SolarEdge, BSLBATT, are just a few of the dozens of home solar battery brands on the market that are being sold and installed every day, with the growth of green renewable energy and subsidies from national policies.
But see here...
In 70% of cases, the installed home solar battery bank does not work properly and does not meet the characteristics of a PV system, thus turning it into a bad investment and unprofitable.
Let's face it, the sole purpose of a home solar battery is to generate savings with the PV system, but often it is not properly utilized, precisely because you buy a product with unsuitable characteristics.
But what characteristics must home solar battery systems have to be efficient? What should you look for when choosing a home energy storage battery to avoid wasting money?
Let's find out together in this article.
1. Battery Capacity.
As the name implies, the task of the home solar battery pack is to store the excess energy produced by the PV system during the day so that it can be used immediately when the system can no longer produce enough energy to power the home load.
The free electricity generated by the system passes through the house, powering appliances such as refrigerators, washing machines and heat pumps, and is then fed into the grid.
The Home lithium battery makes it possible to recover this excess energy, which would otherwise be almost given to the state, and use it at night, avoiding the need to draw additional energy for a fee.
In the Zerø Gas House (which is completely electric), home solar battery storage is therefore essential because, as the data investigates and reports, the winter productivity of the system cannot meet and satisfy the power absorption of the heat pump.
The only limitation if determining the size of the PV system is.
● Roof space
● Available budget
● Type of system (single-phase or three-phase)
For the Home solar battery, sizing is crucial.
The larger the capacity of the Home solar battery bank, the larger the maximum amount of incentive spending and the larger the "incidental" savings generated by the PV system.
For proper sizing, I typically recommend that the lithium ion solar battery be sized at twice the capacity of the PV system.
If you have a 5 kW system, then the idea is to go with a 10 kWh battery bank.
A 10 kW system? 20 kWh battery.
And so on...
This is because in the winter, when electricity demand is highest, a 1 kW PV system produces about 3 kWh of energy.
If on average 1/3 of this energy is absorbed by household appliances for self-consumption, 2/3 is fed into the grid. Therefore, a home solar battery bank of twice the size of the system is required.
In spring and summer, solar systems produce much more energy, but the amount of energy stored does not increase accordingly.
Do you want to buy a larger battery system?
You can do that, but a bigger system doesn't mean you'll save more money. You may want to focus on less and more, or better yet, invest more wisely in a battery system that works for you, perhaps with better warranty panels or better performing heat pumps.
Capacity is just a number, and the rules for determining the size of a home solar battery are quick and easy, as I just showed you. However, the next two parameters are more technical and much more important for those who really want to understand how to find the right product that works best.
2. Charging and Discharging Power.
It sounds strange, but the battery must be charged and discharged, and in order to do that it has a bottleneck, a constraint, and that is the power expected and managed by the inverter.
If my system feeds 5 kW into the grid, but the home solar battery bank only charges 2.5 kW, I'm still wasting energy because 50% of the energy is being fed and not stored.
As long as my home solar battery has power there is no problem, but if my battery is dead and the PV system is producing very little time (in winter), lost energy means lost money.
So I get emails from people who have 10 kW of PV, 20 kWh of battery (so correctly sized), but the inverter can only handle 2.5 kW of charging.
The charging/discharging power also affects the charging time of the solar house battery relatively.
If I have to charge a 20 kWh battery with 2.5 kW of power, I need 8 hours. If instead of 2.5 kW, I charge with 5 kW, it takes me half that time. So you pay for a huge battery, but you may not be able to charge it, not because the system doesn't produce enough, but because the inverter is too slow.
This often happens with "assembled" products, so those I have a dedicated inverter to match the battery module, whose configuration often enjoys this structural limitation.
Charge/discharge power is also a key feature to fully exploit the battery during peak demand periods.
It's winter, 8pm, and the house is cheerful: the solar induction panels are working at 2 kW, the heat pump is pushing the heater to draw another 2 kW, the fridge, TV, lights and various appliances are still taking 1 kW from you, and who knows, maybe you have an electric car charging, but let's take that out of the equation for now.
Obviously, under these conditions, photovoltaic power is not produced, you have batteries charging, but you are not necessarily "temporarily independent" precisely because if your house requires 5 kW and house solar battery only provides 2.5 kW, this means that 50% of the energy you are still taking from the grid and paying for it.
Do you see the paradox?
While house solar battery is charging, you are missing a key aspect or, more likely, the person who supplied you with the product gave you the cheapest system where he could make the most money without giving you any information about it.
Ah, most likely he doesn't know these things either.
Linked to the charge/discharge power is to open the brackets for the 3 phase/single phase discussion because some batteries, for example, 2 BSLATT batteries cannot be put on the same single phase system because the two power outputs add up (10+10=10) to reach the power needed for three phases, but we will discuss that in another article.
Now let's talk about the third parameter to consider when choosing a house battery: the type of battery.
3. Type of Home Solar Battery.
Note that this third parameter is the most "general" of the three presented, since it contains many aspects worth considering, but is secondary to the first two parameters just presented.
Our first division of the storage technology is in its mounting surface. AC-alternating or DC-continuous.
A small basic summary.
● The battery panel generates DC power
● The task of the inverter of the system is to convert the generated energy from DC to AC, according to the parameters of the defined grid, so a single-phase system is 230V, 50/60 Hz.
● This dialogue has an efficiency, so we have a more or less small percentage of leakage, i.e. "loss" of energy, in our case we assume an efficiency of 98%.
● The solar battery charges with DC power, not AC.
Is that all clear? Well...
If the battery is on the DC side, then in DC, the inverter will only have the task of converting the actual energy generated and used, transferring the continuous energy of the system directly to the battery - no conversion required.
On the other hand, if the house solar battery is on the AC side, we have 3 times the amount of conversion than the inverter.
● The first 98% from plant to grid
● The second charging from AC to DC gives an efficiency of 96%.
● The third conversion from DC to AC for discharging, resulting in an overall efficiency of 94% (assuming a constant inverter efficiency of 98% and not taking into account the losses during charging and discharging, in any case).
This strategy, adopted by most storage and Tesla, results in a loss of 4% compared to the other cases.
Now it is important to point out that the intersection of these two technologies is mainly the decision to install home solar battery bank while building the PV system, since the AC aspects are most used when retrofitting, i.e. installing home solar battery bank on the existing system, since they do not require significant modifications to the PV system.
Another aspect to consider when it comes to battery type is the chemistry in storage.
Whether it is LiFePo4 (LFP), pure Li-ion, NMC, etc., each company has its own patents, its own strategy.
What should we look for? Which one to choose?
It's simple: each solar cell company invests millions in research and patents with the simple goal of finding the best balance between cost, efficiency and assurance. When it comes to batteries, this is one of the most important aspects: the guarantee of durability and effectiveness of the storage capacity.
The guarantee therefore becomes an incidental parameter of the "technology" used.
The Home solar battery is an accessory that, as we said, serves to make better use of the photovoltaic system and to generate savings in the home. If you want to have an investment without regrets, you must go to serious and well-trained professionals and companies to buy home solar battery bank.
How can you avoid making mistakes when buying and purchasing home solar batteries?
It's simple, turn to a qualified and knowledgeable person or company right away, BSLBATT puts the customer at the center of the project, not their own personal interests.
If you need further support, BSLBATT has the best team of sales engineers and will be at your disposal to guide you in choosing the most suitable home solar battery for your PV system.