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Cables & Wiring FAQs

Q What do the red / blue / yellow colours of pre-insulated crimp terminals mean?

This relates to the cable size that should be used with them.  Red suits 0.5-1.5mm² cable, blue suits 1.5-2.5mm² cable, yellow suits 3.0-6.0mm² cable.

Q I have cable larger than 6mm² so what terminals should I use for the ends?

For cable over 6mm² you will need to use copper tube terminals.

Q How do I fit copper tube terminals to larger cable?

You will need to use a heavier duty crimping tool such as this one (120mm² max. cable).

Q Can I solder copper tube terminals rather than crimp them?

You can, but it is not recommended in automotive applications due to potential cracking of the solder with vibrations over time. Crimping is also neater, cleaner and less risky than soldering (care must be taken when soldering not to set the insulation alight when heating the terminal).

Q My inverter is rated at 1000W but I how do I know what cable size to use to connect it to the battery?
A For a 12V system divide 1000 (W) by 12(V) to give you 83 (A) (Current = Power/Volts). Now choose a cable that is rated to at least this, plus a margin of safety  - we would recommend 25mm² (170A) in this case to allow for surges.
Q My battery is 120Ah, so do I need a 120A cable to connect it?

No. The capacity of a battery in Ah is unrelated to the cable size you need to use to connect it to a charging source or load. You should rate the cable based upon the maximum charge or discharge current that you expect to put through the cable, plus a margin of safety. This also applies to cables used to inter-connect batteries.

Q How do I connect two identical 12V batteries in parallel?

Connect the positive terminals together and the negative terminals together. This keeps the system voltage at 12V but doubles the capacity in Ah.

Q How do I wire my lighting circuit so that I can switch it on and off from 2 different locations

For a 2-way lighting circuit you will need 2x On/On switches. Each switch has a common terminal (normally the centre terminal) and 2 switched terminals (normally the outside terminals).  Connect your +12V supply to the common terminal of one of the switches, then connect the common terminal of the other switch to the +12V input to your lights.  You then connect the switched terminals of the switches together (imagine a train track running between the terminals).

Q How do I connect two different sized cables together (e.g. small cable to much larger cable)?

Connecting two dissimilar sized cables can be tricky as most connectors are designed to connect similar sized cable. One area where this problem is often encountered is in the above example of extending the cables on a compressor fridge where the flying leads from the fridge are usually quite small gauge but you need to connect to larger gauge cable to prevent voltage drop. The best option here is to terminate the cable ends with suitable ring terminals (normally insulated terminals for cable up to 6mm² and copper tube terminals for larger cable) and then use a terminal block. This provides a professional, secure connection.

Another option if you are connecting two dissimilar cables together that are 6mm² or smaller is to use a splice connector. The cable ends can be terminated with suitable 6.3mm wide female blade terminals and then joined to the splice connector.


Disclaimer - The information contained in these articles is provided in good faith and we do our best to ensure that it is accurate and up to date, however, we cannot be held responsible for any damage or loss arising from the use or mis-use of this information or from any errors or omissions. The installer is ultimately responsible for the safety of the system so if you are in any doubt, please consult a qualified electrician.

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