doveralfa

Both of my classics have a battery isolation switch, otherwise one of them does have a habit of discharging its battery when you aren't looking!
Also acts as another theft deterrent, reduces the chance of fire and makes it easy to isolate the battery when you work on the car. Prevents that accidental short circuit with a spanner across the starter connections doing that 'just job' when you could not be bothered to isolate.
As Cosmo say's some of these trickle chargers are more likely to finish the battery off than keep it healthy.