Re: Electrical safety (was EVrelated(Siemens Electronic Brake))

[Paul G <neong@gte.net>]

Richard Furniss wrote:
>OK, I take the hint, most of my charging is at home, variac now and PFC-20
>soon, so that means a isolation transformer or dose it?,  I have the money
>and it's time to stop the tickle I get from my car.

IMHO it doesn't require an isolated charger to charge safely. It requires
that 2 levels of safety are provided. GFCI, earth grounded frame, and
isolation (transformer) are your choices. You should pick any 2 for
charging outside your garage. You can use only 1 in your garage, but should
verify its working before each charge.

If you use only GFCI you can get a very slight tickle, but not dangerous as
the device will shut down the power if there is more than 5ma (+/- 1ma) of
current between the supply wires. That level of power is not considered to
pose a risk (risk is considered low as it takes about 20ma to interfer with
most persons hearts).

Hooking the vehicle frame up to earth ground will prevent shocks as any
leakage power will return through the ground wire. If this is combined with
GFCI protection then if ground current exceeds 5ma the GFCI will shut
things down. This is a common problem with correctly wired non-isolated
chargers with GFCI protection, espcially with flooded lead cars.

If you go with isolation, you should still use a second layer of safety.
For people using offboard charging its common to use Anderson 50 amp
connectors (or Lester's plug, for users of those chargers), and these lack
a provision for a ground wire. So, the easiest way would be to provide a
GFCI device in the input wiring to the charger. If you are using an onboard
isolated charger its easiest to use a plug type that brings an earth ground
wire into the vehicle, and connect that wire to the frame.

Neon