elias,
neon bulbs are interesting indeed
Heres a picture with a bulb touching the fan grill of my CBA battery tester:



Edit:
Kevin, I tried the setup with a grounding wire and diode attached to the + terminal of the charging battery. If I power my SSG with battery, then everything works fine. But then I tried to run the SSG form a DC power supply. When I turned the power supply on, all the neons started to flash and something started to burn as I could see smoke. I turned the power supply off fast. Turns out that an arc jumped across all the neon bulb leads and this started to burn the soldering plate to carbon that also conducts electricity. I cleaned the space between those leads free from the carbon to prevent shorts. I removed the grounding cable and started the SSG again, this time it run ok, but the amp draw increased 3 times. Turned out that one of the transistors is blown. So an advice to others - DO NOT USE THE GROUNDING WIRE AND DIODE ON + TERMINAL OF THE CHARGING BATTERY IF YOU POWER YOUR SSG FROM A POWER SUPPLY.