Hi all,
Does anyone know what the voltage reading on the battery should be with the headlights on and the bike not running?
My brother picked up an NC30 recently and the reg rec burned out. Got that replaced and was getting 13.5V at 5k revs and had been running great but he seems to be having issues whenever he runs with headlights on. The battery is normally flat after a run out with the headlights on. I couldn't start the bike today but the voltage would drop by about 3V when I turned the headlights on. Is this normal?
Cheers

Sounds like the reg/rec is fucked bud. Did he buy a second hand one?

Nah bought a brand new one. I'll check the voltages tomorrow with the bike running tomorrow.

Check stator output as well then. If that's fucked, it may have taken out the reg/rec.

Charged the battery and started the bike. Seems the R/R is at fault. So the new pattern part lasted 2 days.

What makes you think the rect/reg is faulty? Have you measured the alternator resistance on the three yellow wires at the rect/reg plug with the rect/reg unplugged, have you measured the alternator AC output voltage at the three yellow wires at the rect/reg plug with the rect/reg unplugged?

I measured the alternator resistance and it was 0.5 ohms between all the yellow cables.
With the knackered R/R plugged in I was getting 12.4V at idle and 5K revs. I put on the original honda R/R that we had lying around and it was kicking out 14.3V at 5K and ~13.8V with the headlights on. There's a silhouette nose cone on the bike and it has an aftermarket light fitted as his full beam and with this on the voltage drops to ~12V so is a massive drain.

How many watts is the headlight?

Not sure Magg. It's certainly a hell of a lot brighter/ whiter than the normal high beam on my NC30 so wattage is probably wrong. I'll pull the bulbs out when I next see the bike.
Cheers for the help.

I guess being incredibly simplistic, assuming the low beam is 55w and taking this, dividing by the drop, then multiplying by the drop caused by the high beam, is being too simple? If it's a flat 12V with it on, that would seem to imply about 250W in total!!