[GJim]

> I bought a 12v car horn yesterday with the intent of wiring it into my ebike's power supply

Putting an aerosol fog horn (available from boating supply shops) in the bikes water bottle holder is much simpler, louder and more effective.

[dylan604]

And where does your water bottle go then?

[GJim]

Courtesy forbids me from suggesting where it could go.