Commercializing of lithium batteries some years ago revolutionized battery market. At the beginning restricted to small electronic devices like mobile phones but slowly moving into new areas as long as its price is reduced.
Current cost is due to the complex manufacturing but not due to the main material. Lithium is produced in some countries and it is not expensive. This is the reason because it is expected price reduction in this kind of batteries. Tesla motors is the most exclusive electric car manufacturer and sell the highest range cars. This range is reached thanks to up to 80 KWh batteries. Considering an electric car needs around 20 KWh every 100 Km it is possible more than 400 Km range with this cars.
Coming back to this post topic Tesla motors announced a new battery with a complete different purpose: Our home. Thanks to Lithium reduced weight it is possible to install this battery in a wall and it is manufactured with a different look than normal one.
But, Why a battery in our home? Purposes could be:
- Backup system to supply electricity when electrical network failure mainly when we are not at home.
- Night tariff. In some countries electricity suppliers offer tariffs cheaper during night and a bit more expensive during day. This could store electricity during night to be used during the day.
- Save electricity using solar panels feeding the battery during the day and providing electricity the whole day. Totally isolated or combine with night/day tariff.
Additionally to the battery we need another element for these purposes. This element is a “Hybrid Inverter Charger”. Circuit schema is shown in the following pictures.
This system has two working modes:
- Connected to main electricity network it is connected directly to supply our home network charging the battery at the same time in parallel.
- If no electricity or if we decide to use battery power, home network is supplied from the battery through a DC-AC inverter. Change between two modes is very fast and devices in our home don’t realize of this change.
- Solar panels supplies always the battery.
- Electricity generator could be used instead of main electric network for isolated systems. Only some hours are necessary avoiding generator noise during night.
Cost of hybrid inverter charger is around 1,000 USD added to battery price: 3,500 USD for 10 KWh one (the most recommended) and 3,000 USD for 7,5 KWh one. Adding installation cost we are talking about 5,000 USD cost not including solar panels.
As an example, considering a normal price of 0.12 USD per KWh and 0.06 USD per KWh at night tariff, we would need 84,000 KWh in order to justify investment. At least we have a 10 years warranty offered by Tesla motors.
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