Charging Problem

I have a 2001 CB500SY. It's suddenly developed a battery charging problem where it charges properly except when idling with a load on, such as the lights. Charges OK when revs are up and at idle if lights are off. I thought it may be a faulty regulator/rectifier so I fitted a new one but the problem is still there. Anyone come across this problem before?

This is entirely normal. The voltage output spec is given as 14.0 to 15.5V @ 5000 rpm. The battery doesn't charge at idle if the lights are on.

Well that's great then thanks for that. The bike broke down on a run with a flat battery and I was recovered home. I presumed as it was not charging at idle there was still a fault but looks like new reg/rec has solved the problem. Cheers.

It might have just been you battery was knackered.

However, from personal experience, if you are riding a lot a slow(ish) speeds through town with the headlight on then it is possible that the charging system (even though it is all working) won't charge the battery properly.

I resorted to riding (when safe to do so) with the side-lights only - this made the problem better.

Thanks for your replies. I used the bike all the time for work in all weathers, 40 mile commute part motorway part in town, and never had any problems. When it broke down I got it tested and was told the reg/rec was knackered so I changed it. My guess is that the old one was faulty, so now the battery is not in as good a condition as it was. Charging system seems OK now other than at idle with lights on, so I'll go with it & probably invest in a new battery at some point.

Honda regulators rectifiers are crap, both went on cb and my fireblade as there same part used in both and it damaged batterys, u charge them on battery charger and they be flat straight away or start just once then be flat,