Solar batteries comprise an integral part of solar power systems. They allow us to store the extra energy produced by the solar panels & cells and use it during the downtimes when the system is not operational, that is, at the night or when there is no sunlight for the panels to generate electricity.
Many things should be considered when opting for a solar battery such as efficiency, rating, depth of discharge, maintenance ease, and cost. We have covered the key points here to help you make the right decision.
Solar Panel Battery Bank: Why is it Important
As we all know, solar panels convert the energy from the sun into direct electric current (DC). Since almost all household and commercial appliances run on alternating current (AC), this DC electricity is passed through an inverter to convert it into AC – which is then fed to your house.
So where does a solar battery bank come into the picture? The answer lies in the kind of system you are using for your home solar power.
A solar battery is not needed if you are connected to the grid. Using an on-grid solar system means your downtime power requirements are met by your utility provider while the excess electricity from the panels is supplied to the grid. The final consumption is settled through net metering.
However, with an off-grid system (or hybrid system), solar batteries are critical. Since you are completely independent of the grid, you need to have a backup in place to supply electricity when there is not enough sun for the panels to charge (usually on cloudy/rainy days and nighttime). They are also excellent if you live in an area that experiences frequent power cuts.
Solar batteries can help:
- Reduce the reliance on the utility company – the more energy you store in the battery, the less you need from the grid
- Servee as a backup in areas with long power cuts and outages (we have all experienced this during summer times)
- A cost-effective way of utilising energy; your electricity bills are reduced and the system pays for itself in a few years’ time
Cost of Solar Batteries
Solar batteries in India can cost you anywhere between Rs.5,000 to Rs. 25,000 per unit depending on the factors we have mentioned below. In general, the biggest contributing aspect is the capacity and rating. The overall cost will depend on how many batteries you need to power your solar system.
How to Choose Solar Batteries in India: Factors to Consider
Since solar power for home is a critical investment, it is worth taking time to fully understand the different components that go into it – especially if you are planning to go off the grid.
In the case of batteries, mentioned below are the few things that should take into account.
Type of Solar Battery
A lot can be said about the type of battery for your solar power systems and we have covered the same in great detail here if you are interested.
For the sake of simplicity, solar batteries generally come in two types:
- Lead Acid Battery (Tall Tubular Solar Batter)
- Lithium-Ion Battery
You also have other types of solar batteries like Nickel Cadmium and Battery Flow but in India, people generally opt for one of the two mentioned above.
Lead-acid batteries are economical, efficient, and highly cost-effective. They do not require a lot of maintenance and are easy to work with. On the flip side, they are bulky, heavier, and require a lot of space. Their life cycles vary from 1,000 to 1,500 which is far lower than the advanced batteries.
Lithium-ion batteries can be considered the next step in battery evolution. These have a much higher life cycle (up to 5,000) and efficiency and can store much more charge due to higher energy density. They also have a higher depth of discharge (DoD) which means they can be used to near-full capacity without running the risk of damage or reduction in efficiency. The only drawback is these are considerably expensive.
Solar Battery Rating and Capacity
The next thing to consider is the battery rating. This will tell you how much current the battery can store and release over a period of time. It is expressed in ampere-hours/amp-hours (Ah).
For instance, if you are looking at a 150Ah solar battery, then it means that it can provide 1 amp current for 150 hours or 10 amp current at a constant rate of 15 hours and so on, before being completely discharged. The more the power requirement of your home, the higher capacity battery you will need.
That said, these are ideal calculations. As per the industry standards, solar batteries come with a C rating – C10 or C20. In the simplest of terms, these indicate how long the battery can last (in hours) – and it should not be discharged within that time. C10 is considered to be a fast discharge whereas C20 is a medium discharge.
A 150 Ah C10 battery can theoretically provide a 15 amp current for 10 hours before being completely discharged. However, if this happens the battery life will decrease. Similarly, the C20 battery can last for 20 hours before running out of charge entirely.
The capacity of the battery is determined by wattage rating, which is nothing but:
Amp-hours x Volt
So, a 150 Ah battery with a voltage rating of 12 V can store 1,800 watts of power of 1.8 kW.
You should also remember that batteries are time-dependent since the use of electricity is energy multiplied by time. That is if you use the stored charge for devices that need a lot of energy (air conditioners and so on), the battery will run out faster. By contrast, if you are powering appliances that have a low power rating like fans and light bulbs, the battery will last longer.
Round-Trip Efficiency, Depth of Discharge, Life Cycles
Apart from the aforementioned factors, you should also take into account the quality of the battery which can be determined by:
- Round-Trip Efficiency
All electrical processes are associated with losses. You will never get 100% energy out of anything. The losses will occur when the energy is converted from DC to AC, transmitted to the systems, and so on. Similarly, in the case of solar batteries, round-trip efficiency indicates how much energy the battery can provide. For example, a 1kWh battery with an 80% efficiency can provide 800 watts of power.
- Depth of Discharge
Depth of Discharge (DoD) is an indication of how much energy or capacity can be discharged from a fully charged battery. This is considered to prolong the battery life and keep it operational at high efficiency. In other words, draining the battery completely often is not recommended.
A 5 kWh battery with an 80% DoD means that you should not utilise more than 4 kWh of energy without charging it again. Full discharge is recommended only for emergency cases and for obvious reasons, it is recommended you go with a higher DoD battery.
- Life Cycles
Life cycles indicate how many times the battery can charge and discharge. With time, there will be capacity losses so it is important to go for batteries that have higher life cycles.
Apart from these, there are a few other things you may want to consider:
- Peak and instantaneous power output
- Brand reputation
- Warranty
- Battery Cost
- Ambient temperature/operating temperature range
- Inverter system compatibility
- Ease of maintenance
- Safety
Bottom Line: There’s a Lot to Consider
Clearly, there are many aspects you need to look into when buying a solar battery. Mentioned here are just some of the factors but the bottom line is your power requirement and budget will lead the way. Since solar systems are an investment in your future, we recommend going with the best of the best batteries so they can last long without repeatedly burning a hole into your pocket. To that end, the batteries you see on this page have been chosen after thorough research to help you make a quick, effective decision.