1978 CB550k. Antigravity 8cell Lithium battery (brand new - no over discharge issues). OEM electronics and charging system. Wiring was shortened, cleaned up, run under tank. Electronics moved to under seat. Started the build a year ago and just finished it today. Went to start bike today and it started easily and ran really well. After 8 minutes or so the headlight started getting dimmer and dimmer until the bike shut off, battery was dead. We checked the voltage right away and it was at 8volts. Put on the special tender/charger I bought, it was at 10.5volts after about 10-15 minutes. Does this sound like a wiring issue (possibly bad ground)? Or is it an electronics management issue (need modern charging system - possibly new regulator/rectifier)? Any help would be greatly appreciated. Thanks