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Author Topic: Low Voltage, weak starter, slow flash  (Read 1720 times)

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Offline OldSchool_IsCool

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Low Voltage, weak starter, slow flash
« on: July 17, 2006, 07:07:18 PM »
Hello All!

A GREAT forum you have here!  I've been reading/searching this site for a few Weeks now.  I have a question to which I haven't been able to find an answer right off.  If someone could point me in the right direction, wonderful or if anyone has the answer strait off, great!

I have a '77 550k rescued for certain scrapage.  I got it last fall in a non-running condition (a short was popping the main fuse when key switched on)  Previous owner was moving and gave it to me as a thank you for helping with his move (or maybe because he didn't have space for it in the van!  ;) )

At any rate, that problem has gone away since I cleaned all connectors and wrapped the wire harness wherever it might possibly chaff.  (never did positively ID the actual short, however)

The problem I'm having now is a very weak battery.  After a 20-minute run today, it sat for a few hours.  I checked the battery fluid levels and they are spot on in all cells.  With the ignition off, the battery measures 10.5 volts.  I kick start it (yes, Old School IS Cool!) and measure voltages of 12.5v at 3k RPM and 14.0v at 5000 RPM.  The headlight on this model is on all the time.

Other symptoms besides slow/worthless cranking is slow/stalled turn signals.  The brake light is a sufficient enough a power draw to stall the turn signals (hand signals and clutch work not mixing too well! :( )

So what do you think?  Bad Battery? (new last fall, spent the winter inside, trickle charged before spring riding), Alternator? (though other threads say a bad alternator is rare), Bad regulator? (I could see that if charging voltage was over 14.5v) or maybe the rectifier?

Again, GREAT forum and thanks for supporting it!
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Can I have a motorcycle when I get old enough?
If you take care of it.
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Lot’s of things. You’ve been watching me.
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Offline Bodi

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Re: Low Voltage, weak starter, slow flash
« Reply #1 on: July 17, 2006, 07:20:11 PM »
Possibly if you fully charge the battery with your trickle charger, all will be well. It's likely that your battery is done though, sitting unattended over a winter will do that. The battery self-discharges and if it sits fully discharged for long it's toast. There is a chemical you can add to reduce the plate sulphation but probably a new battery is the best thing, if you can get a hygrometer and check the electrolyte SG at full charge you can know more about the actual condition.
The charging system only charges the battery at higher RPM, as you measured. If you go for a long highway ride it should get a nice full charge, city riding will usually deplete the battery slowly.
There's not much extra power for charging the battery at the best of times, and a discharged battery can sometimes just never catch up once it gets down enough. Removing the headlight fuse during daylight riding is a good enough way to get a discharged battery charged up in a pinch.
Disconnecting the front running lights and using a LED tail/stop light reduces the constant power load quite a bit and that usually solves charging problems when everything else (wiring, alternator, rectifier, regulator) is OK.
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Offline TwoTired

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Re: Low Voltage, weak starter, slow flash
« Reply #2 on: July 17, 2006, 11:27:22 PM »
Quote
With the ignition off, the battery measures 10.5 volts.  I kick start it (yes, Old School IS Cool!) and measure voltages of 12.5v at 3k RPM and 14.0v at 5000 RPM. 

A charged battery should have 12.6 V  (2.1 v per cell; 6 cells), and should maintain that voltage overnight. Either your battery has a dead cell, or it wasn't fully charged when you stopped the engine.
Your RPM tests show that the charging system is working.  But, a depleted battery will take time to charge up to peak voltage.  A bad one never will fully charge.
Although the bike can charge it, it's going to take between 30-60 minutes @ 5000 RPM to recharge a good depleted battery.  Subtract double any time spent below 2000 RPM.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
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Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline OldSchool_IsCool

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Re: Low Voltage, weak starter, slow flash
« Reply #3 on: July 18, 2006, 06:38:54 AM »
Thanks for the info.  Yes, most of my riding over the past few weeks has been low RPM, short, city type trips.  I'll put the charger on the batt overnight tonight and see how she does.  If the battery is toast, then it's a leasson learned.  Guess I'll just have to tell the wife that I gota go do "battery maintenance" and take a nice, long, high RPM spin! (shhhh don't tell her about battery tenders if you please!)

A side question:  Should the battery be disconnected from the bike during charge/tending?  If yes, should I disconnect the positive, the negative or both?
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Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline Bodi

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Re: Low Voltage, weak starter, slow flash
« Reply #4 on: July 18, 2006, 07:29:54 AM »
No need to disconnect. The battery is as charged as it's going to get when all cells start bubbling. Further charging will just bubble away the liquid. The gas produced is an explosive mix of hydrogen and oxygen, don't ignite it.
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Offline bryanj

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Re: Low Voltage, weak starter, slow flash
« Reply #5 on: July 18, 2006, 07:45:05 AM »
You could get hold of a UK model RH switch unit from www.davidsilverspares.co.uk that will alow you to turn off the headlamp, not a requirement for it to be "on" in the UK Or just put a tender on it every time you park up, probably with a "New" 12N12A4A-1 battery
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Offline OldSchool_IsCool

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Re: Low Voltage, weak starter, slow flash
« Reply #6 on: July 19, 2006, 08:02:04 AM »
Last night, I rode her hard for about 20 miles.  I selected cruising gears that allowed the engine to rev in the 4k to 6k range.  When I parked her, the battery read 12.2v.  An hour later, 12.1v.  In the morning, 12.1v and holding.  That's with NO charger assistance.  I was able to start her with the start button this morning and the turn signals were perky on my short ride to work.  She seemed happy again!

Maybe my issue is truly MY issue, that I baby her too much, keeping the revs down too low.  I need to take the hint that she red-lines at 9k!  That she likes it rough.

Guess I've been a cager too long!
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Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline TwoTired

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Re: Low Voltage, weak starter, slow flash
« Reply #7 on: July 19, 2006, 08:51:07 AM »
In battery parlance, 12.1V is not fully charged, and indicates a weak battery.  You do not have a dead cell.  But, it needs to be float or soak charged to fully saturate the battery electrolyte and reverse as much of the sulfation as possible.

One of these works well:
http://www.yuasabatteries.com/chargers.asp#Order

Or, something quivalent.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline OldSchool_IsCool

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Re: Low Voltage, weak starter, slow flash
« Reply #8 on: July 19, 2006, 09:18:56 AM »
I thought that might be the case since the 12.6v stated earlier in the thread was not achieved. I have a charger already and will hook her up tonight since I can't take her out for a "battery maintenance" spin..

Thanks all for your assistance!  Being a new rider, I have much to learn.  Is there an article anywhere on "What a new SOHC owner needs to know"?
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Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline StevieMac

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Re: Low Voltage, weak starter, slow flash
« Reply #9 on: July 19, 2006, 10:35:46 AM »
You can start with the FAQ section:
http://www.sohc4.us/forums/index.php?board=11.0

If you have time just start reading through all the posts in the tech forum. 

Cheers,
Steve
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