Installation & wiring
How do I install an inverter?
Install it indoors on a flat, dry surface, where weather and the elements cannot get at it. Keep it within fairly close range of the battery bank so the DC run is short and the supply to it is clean.
Why is 12V cable so much thicker than house wiring?
Because lower voltage means more current has to be moved for the same amount of power to be transferred. The formula for power here is power in watts equals Volts times Current in Amps, P=VxI.
If we rearrange the formula for current it is I=P/V. So, we can see if power is kept the same, and the voltage gets lower then the current 'I' will get higher, for example halving the voltage from 24v to 12v would double the current.
Some examples for the same power of 1000W , ~4A at 230V but is ~83A at 12V and ~41A at 24V.
What's the real rule for cable sizing?
People usually spec cable only by maximum current. The other main criterion is resistance and the resulting voltage drop - and also crucially knowing how voltage-sensitive the two things it connects are. Some links barely care about losses; others need much thicker, lower-resistance cable.
Use our Voltage Drop calculator, which will tell you what voltage drop and cable size you need to be in the green, depending on how voltage sensitive your application is: https://waveinverter.co.nz/calculators/dc-voltage-drop/
What voltage drop should I aim for?
As a general rule keep it under about 5% for less sensitive links such as generation transmission e.g. from your solar/wind/hydro. More sensitive connections are high current paths between batteries and inverters, to pumps and other large loads. Least sensitive is non-critical lighting.
The most sensitive are usually links used for battery charging as the consequence of voltage drop is not just lost power but improper battery charging causing your batteries to wear out faster, aim for under 1% losses for these links.
Always calculate based on the round-trip length, not one way.
Use our Voltage Drop calculator, which will tell you what voltage drop and cable size you need to be in the green, depending on your application: https://waveinverter.co.nz/calculators/dc-voltage-drop/
Why does my long cable run need such heavy wire?
Resistance rises linearly with length, so a long run drops progressively more voltage. Either go thicker, shorten the run, or raise system voltage to reduce the current.
Do lugs and crimps really matter?
Hugely, a bad crimp can add more resistance than metres of cable, right where current is highest. Use proper hydraulic/hex crimps on heavy lugs; never rely on a twist-and-screw.
Should I tin the ends of stranded cable with solder?
Generally, no - large solder work hardens and flows over time, creating a loose, high-resistance joint. Crimp a proper lug instead, or only apply a tiny amount of solder to help stop the lug sliding off.
Do you make up custom cables?
Yes, tell us length, gauge and lug/terminal type (e.g. an 8mm eye one end) and we'll make it. Custom battery leads are a regular request off the chat. Or tell us what you are connecting and we can calculate what cabling is required to make it work reliably.
What cable do you use for high-current DC?
High-strand-count flexible battery cable for minimal loss on high-current runs, giving enough flexibility and with tinned lugs for corrosion resistance.
Where should the fuse go?
There are multiple influences on this, close to the battery/power source is common. It is more practical to have your fuses and circuit breakers in one place and that one place be close to where you would notice an issue or sited where there is easier access. Ideally you want to be able to notice there is an issue by looking at monitoring or noticing tripped breakers and immediately operate the isolation to make the system safe, not going around to different places hunting for them to do that.
Can I run AC and DC in the same loom?
Keep low-voltage and extra-low-voltage systems physically separated and isolated - that's now an explicit requirement in AS/NZS 3001.2:2022 for relocatable installs. For example, you must have AC and DC circuit breakers in different enclosures that are separated by an air gap.
Do I need an electrician?
For 230V AC work, in general yes, though there are some exclusions for homeowners that also get the work reviewed by an electrical inspector. It must be done to AS/NZS 3000/3001.2 and certified. The 12V DC side you can generally do yourself with correct cable, fusing and connections.
What's the safest battery bank layout?
For parallel connections, the priority is to minimise difference between parallel paths, so match cable lengths for this. We use different cabling structures to do that and also bus bars especially as the number of parallel connections increases.Batteries in series need closer monitoring as even a small issue with one can have significant negative effects on the others that are in series with it. But the cabling is simpler for series connections.
Equipment we use to design this include parallel links, series links and bus bars. Secure your battery bank in a ventilated box or rack, with a main fuse and isolator. We sell the boxes, racking and protection.