A Guide To Using Batteries For Home Power Storage

August 12, 2016

home energy storage battery

On our previous article here, we have discussed the possibility of powering your home solely with battery power. The electrical giant Tesla pioneered, and popularized the easy-to-install home battery with the Powerwall, being an instant hit since it was released in 2015. Other big companies including Panasonic, LG, and Samsung are soon following with their version.

But is it technically viable? Will it be safe? For most of us, wiring our house with 100% DC power is something new, even unimaginable, and it's a very human nature to fear the unknown. However, we should remember that yachts and RVs run on batteries, and we've seen, and experienced how safe they are.

In this article, we'll dig a little bit deeper about using batteries to power our homes, starting with discussing its safety.

How Safe Will a Battery-Powered House Be?

The answer is: Very safe. When designed and wire correctly, using DC currents to power your house can be even safer than your old AC counterpart.

DC voltage cannot electrocute when touched by skin, only causing heat burns, even when you stand in water. Even the heat burn will only happen when you touched both the positive and negative (ground), which is an extreme rarity. Compare it with a case with an AC current, that even making a contact with either the positive or the ground can cause electrocution and even death.

Consider your car as a case. A typical 12-v DC battery of a car can have 700+ Amperes of current running through it in an hour. Compare it to a house with 10,000 Watt capacity, and average 100 Watts usage per hour.

The house will 'only' have around 100 Amperes of current every hour, a seventh of what you have in the car. Did you ever get electrocuted in your car? Most likely not, except if you touch both polarities of the battery directly.

This is caused by the low-voltage state of the DC current used in batteries. Your batteries typically used 12-Volts of voltage, compared to 120-Volts or 230-Volts in AC counterparts. So to answer the question of safety, it's a definite yes.

How Efficient?

Another definite yes. In our previous article, we also have discussed how Google's Larry Page argued that using a dedicated DC current to power our DC computers can save more than 40 billion KWh over 3 years, equivalent to $5 million Dollars.

Many of our appliances are of DC nature, and powering it using AC currents will need inverters or adapters. AC adapters power supplies, especially the linear ones have an average efficiency of only 40%-50%, while even the most advanced ones peaked at about 90% (80-ish % being more common).

Bypassing the need for adapters alone can save you at least 10% more energy, and can be as high as 70% with proper design and control system.

Convinced yet? But how about when the Tesla Powerwall is not available in your location? Or simply too expensive? There are cheaper alternatives currently available, such as the Adara Energy Storage, or the Sunverge SIS, and in the very near future more products will be available with cheaper price.

Other solar batteries, with lead acid instead of Powerwall's lithium-ion, have also been available for a while and can be cheaper alternatives. Contact your local off-grid or solar contractors for pricing and installation.

Still not an option for you? How about building one from scratch?

Building Your Own DIY Battery

A 7 KWh Tesla Powerwall will cost you $3,000, not including installation and wiring by certified Tesla technician that will cost you in total around $15,000.

While it will still save you money in the long run, compared to paying your power company, building a battery on your own can save you a lot more. In fact, a YouTuber named Jehu Garcia showed us how to make one with only $300.

Another one, UK DIY POWERWALL has a bit different approach. His version cost only $900.

In fact, it's easier to build than the traditional lead-acid batteries. If you're a big fan of DIY or want to try something new, we certainly encourage you to try to build your own battery.

Wiring and Installation

After you got your battery ready, here comes the next step: wiring your house to the battery itself. This can be a highly confusing task, especially if you are using multiple batteries.

Here are a few considerations:

  • Serial or Parallel: Wiring two batteries in parallel (positive connected to another positive, negative connected to negative), will sum the capacity of both batteries. Wiring in series, on the other hand, will increase the voltage, while keeping their capacity intact. Both have their one uses, so keep that in mind.
  • Determining Voltage Needs: For optimal use, the battery should have the same voltage as the charging device. E.g. if your solar panel produces 48-volt of voltage, and you have two 24-volt batteries, it's best to wire them together to make a 48-volt battery.
  • Location: Choose a well-ventilated yet sheltered location. Your electrical panel is usually placed in such spot, and this simplifies things because you'll generally want your battery close to your panel so that you won't need as much wire.
  • Charge Controller: You'll need a charge controller between your generator (solar panel/wind turbine/others) and the battery. The charge controller regulates the rate of currents from charged or being drawn from the battery, preventing overcharging and overvoltage.
  • Inverter: If you plan to use your old appliances and stick to the 120/230-Volt, you'll need an inverter on your battery output. As mentioned, an inverter will reduce your efficiency, and we recommend re-wiring your house for DC current. Reader's discretion is advised.

Here is a nice wiring tutorial, complete with wiring diagram from markp0177, as well as one from Free Sun Power for those who preferred text guides. Remember, although most guides are for solar photovoltaic system (as it is more popular), they can easily be applicable for wind turbine systems.

End Words

This guide should cover the basics of running your house on a battery, from buying or building your battery to wiring and installation. Is it time to upgrade your house with a DC battery? Maybe so, and it will be a profitable investment in the long run.

With more options and expected price drop in the very near future, installing a home battery will be cheaper than ever, and don't forget we can build even cheaper ones ourselves.

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