(Why) are IEC C5/C6 connectors a necessity? Why not use C13/C14?

Solution 1:

There is a significant difference between the connectors. It is the current handling ability.

Basically, the C5 connector enables manufacturers to make smaller, lighter weight, less expensive power cables, because the C5 connector should never be used in a situation where overall current draw is greater than 2.5A.

A cable with a C13 connector that could fail/melt when subjected to a current draw of >2.5A would leave the manufacturer vulnerable to liability lawsuits. However, a similar cable would be fine with a C5 connector.

In the end, the C5 connector is not as common as the C13, so in situation where the minor cost saving of the C5 cable is mitigated by the lack of volume, the C13 connector is used, which is why you see it on laptops.

Solution 2:

I have often wondered this, as they are an inconvenient outlier for those laptop power supplies that use them. The main reason seems to be cost and size.

As mentioned the C5 connector is rated for 2.5A compared the C13 10A rating. This means less material is needed to produce them since the physical size of the plug and socket can be smaller and the cable wiring size can be reduced as the current capacity will be a maximum of 3A, protected by a fuse.

The strange part is that a lot of laptop chargers that require a C5 connector provide a three core power lead with 0.75mm² wire size that is over-rated where 0.5mm² (3A max) would be perfect and be more portable.

It does pose the question, why not use the even smaller C7 (figure-8) connector with a 3A cable which does away with the earth connection. However, whether the earth is required is another question with no satisfactory answer: Do I need earth?

Just to note that most C13 computer leads have three 0.75mm² core leads with 3A or 6A fuses.