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Batteries

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Batteries are big, heavy, costly, often highly toxic and will not last forever – all the things you do not want to hear.

  • For more detail on this topic read our battery guide.
  • For more detail on battery enclosure and powershed design click here.

These are your main options:

Wet lead (lowest cost). Can work very well on off-grid sites with small hydro turbines. Low cost but if you want a 7-10 life you have to ensure shallow cycles of only 10-20% of battery capacity. Top up water is needed every few months. Life is typically 3-5 years when used off-grid on solar PV homes. Both U.S. battery and Trojan 6V L16 type cells are a good option and available in NZ. Warranty typically 1-2 years.
Sealed lead (higher cost). Best suited to large off-grid solar PV systems. Sonnenschein Gel would be a good brand to choose. Lives up to 10 years are possible. Warranty typically 2-6 years.
Advance lead (highest cost) - often called VRLA Nano Carbon (higher cost). Best suited to grid-tied solar PV home or off-grid with hydro. They can be deeply cycled but like all lead batteries must not be left in a low state of charge for any significant length of time or they will suffer capacity loss due to sulphating. Century Yuasa would be a good brand to choose. Lives >10 years are possible. There are a number of less reputable brands claiming 20-year life with short and onerous warranty procedures - avoid these brands. Warranty typically 3 years.
Super capacitor storage (highest cost). This storage option is still relatively new. KiloWatt Labs marketing by Green Fox in NZ may be a good option to consider. They claim of up to 45 year life but only a shelf life of 10 years. Warranty is also 10-years and conditions are difficult to fully understand. Their warranty document does not clearly tell you what the limited warranty actually covers - mainly what it does not cover.
Lithium (highest cost). They are many lithium batteries on the market these days. Their high cost means that they tend to find uses in smaller applications. They are typically used to give grid-tied homes some limited self-consumption at night. But at current prices this does not look to be economic for the end client. Very few lithium batteries are made for off-grid applications at this time. Simpliphi (Lithium Ferro Phosphate) are a leading band – they offer a 10-year warranty.

 

If you are intending to live off-grid, batteries are essential unless you have a large 5kW+ hydro resource. If you have adequate intermittent all year generation from opposite renewable energy sources (such as solar PV and hydro) then you can often manage with a smaller battery bank (provided you are frugal during times that are overcast and dry and/or are prepared to use a fuel generator).

Remember most battery sales representatives do not live off-grid through a NZ winter (where the sun may not shine for days). Their advice is often based on a sales blurb and margins and not always on a solid customer experience.

There are many battery types on the market, if you intend to live off-grid and want the perfect battery experience and no limits on your power consumption (and no 2nd mortgage to go with it), then we suggest you do not live off-grid. If you want the freedom to use plenty of power whenever you like you will need the grid to support your system automatically. If you are prepared to be careful at times, invest in a renewable energy generation system large enough to power your home all year, then existing battery technology can work well from a battery cost of about $1000-2000 NZ per year. This cost can be much higher for larger off-grid home that are mainly solar PV powered.

If the grid exists already at your home we do not advise you go off-grid. You can consider grid-tied or grid-assisted systems which may require no battery or only require a very small battery.