Battery not charging with lights on

My battery is not getting sufficient voltage to charge when the lights are on, put a multimeter across the battery and its getting 13v+ with the lights off but if I turn the lights on it drops to around 11.5. Proccess of elimination I guess to find the cause, first thing I will do is clean up the earth connections and see if that resolves it then next I guess its a reg/rec replacement? The battery has been replaced recently but the reg/rec is still the original oem part to my knowledge, bike has done 22,000 miles. Whats the general consensus? Ill let you know what was at fault when its sorted.

[NedSVS]

Don't buy a new regulator until you have checked all the connector contacts are clean and corrosion free. Dirty contacts = high resistance and a voltage drop; the more current you draw (eg lights on) the bigger the voltage drop. I'm sure many voltage regulators have been replaced unnecessarily beause of this: Of course a new regulator comes with shiny new clean contacts and appears to have fixed the problem!

[Biker Biggles]

When you checked the charge rate did you do the alternator output as well?Should read about 70 volts AC on all three coils.

Originally Posted by Biker Biggles

When you checked the charge rate did you do the alternator output as well?Should read about 70 volts AC on all three coils.

I didn't as it was the AA man who had the multimeter, Id stopped on the side of the a34 to stretch my legs and have a ciggy yesterday morning and the battery was flat as a pancake when I got back on. I will do though to rule out the alternator.

[yorkie_chris]

It's likely the reg rec but obviously eliminate everything before spending money.

No need for a poll either, there are various troubleshooting guides around from people who know what they're on about, why ask everyone who can click a button based on what their mate said 5 years ago?

Originally Posted by yorkie_chris

No need for a poll either, there are various troubleshooting guides around from people who know what they're on about, why ask everyone who can click a button based on what their mate said 5 years ago?

I've not yet had a problem with a reg/rec, so might be a problem to do with not riding fast enough to charge the battery up, maybe put a higher octane fuel in

Originally Posted by yorkie_chris

It's likely the reg rec but obviously eliminate everything before spending money.

No need for a poll either, there are various troubleshooting guides around from people who know what they're on about, why ask everyone who can click a button based on what their mate said 5 years ago?

The poll isnt going to affect the course of action I take, I just stuck it up as a bit of fun to get the general conesensus and see how many guessed right when I fix it. I was looking for general advice/tips from others though, which I have recieved, so thanks.

T'was the reg/rec. replaced it with a late model CBR600 item. I chopped the connectors off the old oem r/r and crimped them onto the new un. Plenty of leccy tape appplied and it looks almost standard. Perhaps not the most elegant solution but wanted to avoid chopping up the loom. Getting 13.8 v accross the battery at idle with lights on now.

Originally Posted by benji106

T'was the reg/rec. replaced it with a late model CBR600 item. I chopped the connectors off the old oem r/r and crimped them onto the new un. Plenty of leccy tape appplied and it looks almost standard. Perhaps not the most elegant solution but wanted to avoid chopping up the loom. Getting 13.8 v accross the battery at idle with lights on now.

Wooo, I voted right! And no I didnt read the answer here!

As a side note. Id advise cleaning all of the connectors up as well, it could help in the long and short term!

Originally Posted by ThEGr33k

Wooo, I voted right! And no I didnt read the answer here!

As a side note. Id advise cleaning all of the connectors up as well, it could help in the long and short term!

Yep that was the first thing I checked, they didnt look corroded but got a good blast of WD40 anyway.