CB550 Voltage Drop - Electrical Issues

[titan5699]

Hey guys!

I'm getting some weird electrical issues with my 76 CB550.

With a fully charged battery connected, and the ignition off, I get a normal (12.5 or so) voltage reading. When I switch the key to on, the voltage drops to about 9v and will keep dropping. When I flip the key back to off, the voltage will begin to rise again to about normal or slightly below the 12.5v. If I turn the key all the way to the "Park" setting, I will get a slight voltage drop (low 12.xx volts or high 11.xx volts) due to the lights being on. If I am quick enough, I can turn the ignition to on and use the kick starter to run the bike before the battery drops too low. While running the voltage does not go up or down as long as I am at about 3K rpm or higher. It will stay at around the 8.xx volts. Below 3K rpm, it will continue to drop, which is normal for that bike when everything was running properly. Below 3K rpm (like if it were sitting at idle) it will not recharge the battery.

I have tried to remove the tail light and the head light fuses to see if that would change anything, but no difference. Also replaced the main 30a fuse with no difference. No fuses were blown during any of this.

I have tested the aftermarket regulator/rectifier unit, and it seems like the diodes are not properly functioning so I swapped out for the original separated rectifier and regulator units. I tested the original rectifier and I got good readings for the diodes. Now when I run it, I get better voltage readings, at about 3K rpm I get 13.xx volts. I tested it all the way up to about 6K rpm and was getting readings in the high 15.xx to low 16.xx volts. That seemed high to me if the regulator is properly working, but I am not sure with the original regulator. The aftermarket regulator/rectifier unit I believe would cap the voltage at about 14.xx volts when it was working properly. But for now I left the original rectifier and regulator units on the bike since I got better results with them. I think the aftermarket regulator/rectifier is no good. I was hoping that would solve the issue of the voltage dropping, but nope. Biggest difference with the original parts back in is that the voltage goes back up like normal when running at about 3K+ rpm.

I had the aftermarket unit in for about 1-2 years with no issues before, in fact I was riding it regularly up until this issue showed itself. I washed it the day before this happened, to get it all nice and shiny for the Distinguished Gentleman's Ride the next day. I ran it for a little while after I washed it to make sure everything was working properly and to dry up some of the water left on the bike. I put the bike away for the night and put it on the battery tender (which I have done numerous times). Wake up on Sunday to get the bike out and warmed up for the DGR and no power at all. I checked the fuses, all were good, changed the main fuse just for good measure, no difference. I checked the voltage, the battery was completely flat, actually reading about 0.01x volts. The battery is about 1 year old and is a gel battery. I charged up a back up battery, and had the same outcome when I left it on the battery tender and hooked up in the bike for a night. Both times, it took a normal reading battery and completely depleted it over night while being on the battery tender.

I have been looking for loose connections and exposed wires, Ive thoroughly cleaned the ground connection and battery terminals. I am just puzzled why the voltage drops when the ignition is turned to ON, but doesn't do it when OFF or on PARK. It might be something simple and stupid that I am over looking, so please, if you have any suggestions let me know.

Thank you for your time and assistance.
-Rob

 

[d9canada]

The 550s and all SOHCs for that matter use a different type of alternator using a field coil, not a permanent magnet rotor like the DOHCs and the integrated regulator/rectifier for the DOHCs is NOT the right thing to use on an SOHC. If your old originals don't work, get replacements of that type. You'd have to check the FSM for test procedures for those parts. As I just responded to another guy about charging on an SOHC, http://www.motorcycleproject.com/text/booknook.html#13 is a good guide and that site is a very good site generally. Just be careful not to mix up DOHC info with SOHC.

 

[Sonreir]

The DOHCs use an electromagnetic alternator, not a permanent magnet one. That's a bit off topic though, I suppose.

Rob,

How new/old is your battery? It might just be toward the end of its life. Do you have a different one you can swap in to see if the symptoms persist?

 

[titan5699]

The 550s and all SOHCs for that matter use a different type of alternator using a field coil, not a permanent magnet rotor like the DOHCs and the integrated regulator/rectifier for the DOHCs is NOT the right thing to use on an SOHC. If your old originals don't work, get replacements of that type. You'd have to check the FSM for test procedures for those parts. As I just responded to another guy about charging on an SOHC, http://www.motorcycleproject.com/text/booknook.html#13 is a good guide and that site is a very good site generally. Just be careful not to mix up DOHC info with SOHC.

Thanks for the info, but the integrated unit is meant for SOHC 500's and 550's. It is manufactured by Rick's. And it has worked for the better part of a year with no issues before. And all the connections were direct connections of the original equipment. Not sure if that means anything, but thought I would mention it. It's possible that the aftermarket part still isn't as good as the OE part, or possibly its a bad unit, or maybe even something else went bad and took that out as well. Because even with the OE parts, it does charge better when running, but as soon as the ignition is turned to ON, it still drops my voltage and keeps draining it very quickly.

 

[titan5699]

The DOHCs use an electromagnetic alternator, not a permanent magnet one. That's a bit off topic though, I suppose.

Rob,

How new/old is your battery? It might just be toward the end of its life. Do you have a different one you can swap in to see if the symptoms persist?

Thanks for responding, but as I mentioned in the original post (sorry, yes I know it was a bit long and over explaining, lol), I have tried 2 batteries. The one that was in the bike when the problem first happened was less than a year old Bikemaster Trugel battery. I had no issues with the battery at all. But since the battery was completely depleted, it wont charge up again. For now I have been working on it with a back up battery that I have that is less than 2 years old. Just a standard battery from Pepboys. It was stored on my shelf once I got the Trugel. I just replaced it with the better quality gel battery, but it was working fine when I took it out of the bike about a year or so ago. I did charge it up completely with the tender before sticking it back in the bike after this current issue drained my gel battery.

So I don't believe there is a problem with either battery, and I am having the same results with either battery.

I am thinking there might be a short somewhere but I am not certain. I don't know if the voltage drop is normal behavior if there were to be a short. Or maybe even a short in the ignition switch since I only have the drop when the key is ON, not when its in PARK or OFF. Or a short in something that powered up when the ignition is ON and is cut off from the battery when the key is in PARK or OFF.

 

[Sonreir]

I wouldn't dismiss the battery as the cause just yet. Gel batteries don't last too long if your charging system needs work and a battery that has been sitting for a year or more off the charger is likely to be dead beyond salvage.

Most shorts capable of causing a voltage drop of three volts in a healthy battery are almost definitely pulling enough current to blow a fuse. If your fuse is still intact, then the battery isn't producing much current.

With your car engine turned off, run some jumper cables from the car to the bike battery and see if the problem still occurs.

 

[titan5699]

I wouldn't dismiss the battery as the cause just yet. Gel batteries don't last too long if your charging system needs work and a battery that has been sitting for a year or more off the charger is likely to be dead beyond salvage.

Most shorts capable of causing a voltage drop of three volts in a healthy battery are almost definitely pulling enough current to blow a fuse. If your fuse is still intact, then the battery isn't producing much current.

With your car engine turned off, run some jumper cables from the car to the bike battery and see if the problem still occurs.

I guess you are right, I should never dismiss anything lol. It's worth a shot to try a new battery.
As for connecting it to a car battery, would a full size truck battery be ok? Or too much? And can I do that with the battery out of the vehicle or best to leave it connected to the truck?

Thanks.

 

[Sonreir]

No such thing as too much battery. Your bike will only pull as much current as it can handle (assuming you don't have a short).

Leaving it connected to the truck is fine.

 

[titan5699]

No such thing as too much battery. Your bike will only pull as much current as it can handle (assuming you don't have a short).

Leaving it connected to the truck is fine.

Ok thanks. Ill give that a try before buying a brand new battery again.
Ill report my findings after.

Thanks again!