On 17/03/2019 14:18, Dave Plowman (News) wrote:
Old car needed the battery charged.

Plugged that in via an extension lead from an outside socket - which has
an historical RCD just inside the house - from before when I fitted a
modern split load CU with RCD.

Charger was working and showing a charge, so left it to get on.

About an hour later, the house RDC tripped.

Unplugging the charger got things back to normal.

5 amp fuse in the charger plug had blown. Charger is an all plastic type
with a two core mains lead.

What sort of fault inside the charger could have caused the RCD to trip?

Leakage from live or neutral to earth via the battery charging side
through the car body to ground? If it's an old charger, then
transformer breakdown could be the issue.

Cheers
--
Clive