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Hi

First a little background.

I have a 25 year old 250 Virago that was left for 15 or more years. I have ridden it for about 5 years and the electrics often need attention. I have replaced the rectifier/regulator twice as they "go bad" - delivering 15 to 18 DC volts as they fail - and I have bought "good quality" RRs in the past as well as EBay cheapies.

Now the problem. Yesterday the bike had no power, no lights, no neutral jewel light etc. I tested the main fuse and it was fine. I have hooked up a battery charger and the neutral jewel bulb lights up , the battery/charging voltage reads around 13.2 V when charging with nothing switched on. If I switch on the ignition and the parking lights, the charging voltage drops to about 12.8V. However, when I switch on the dipped headlights the charging voltage falls to about 6.5 V to 7V. Is this drop in voltage expected when charging a badly discharged battery? Is the drop in voltage when switching on parking lights a hint of a different problem that explains why the battery discharged?

I need to check the alternator and rectifier again. What a pain.

Thanks,

Clive
 

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This site requests you introduce yourself before asking questions so people know you are serious and not a post and run type poster. Introductions found here ... https://www.motorcycleforum.com/forums/new-member-introduction.305/
On average charging on most bikes is around the 14v. It is normal for the battery to drop when turning on lights and such, however, 7v is far too low. Id also expect for the 13.2v to be after turning on the lights not with everything turned off. If you're absolutely sure the reg/rec isn't the problem you could try testing the 3 phases coming from the stator.
 

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The symptoms you are reporting can be caused by a battery that has a dead cell or a defective interior connection. . I just got through dealing with one -- battery less than three months old, read as fully-charged after charging but immediate and drastic voltage drop when put under load. A new battery "cured" the problem.
 
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