Low voltage and dying battery


Playtex11

Low voltage and dying battery

Post by Playtex11 »

1980 CBX-SS. It will take a charge from the trickle charger up to about 12.5 volts on the bike ammeter and it will start the bike. It drops voltage steadily after 10-15 minutes of running from the 12.5 volt range. It never gets up to it's usual 13.5 to 14 volts while running. If you shut it off and try to restart, you just get the clicking solenoid noise and really dim lights. Then you have to recharge the battery to get it to start again. All I checked were the fuses and they are all OK. I have a good battery I can put in it to check if that is the problem. Should I try that first? I also read in this forum to check all connections for corrosion and I will do that tonight after work.

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Re: Low voltage and dying battery

Post by tevan »

I would have battery checked. Just because you have 12.5 volts doesn’t mean you have the amperage. I would take the battery and get it load tested.

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Re: Low voltage and dying battery

Post by Larry Zimmer »

First thing I would do is get the bike started. Then, using an outside meter, check the voltage across the battery terminals with the engine at 3000 rpm. The volt meters of these bikes, with the circuitry, are notorious for not indicating true battery voltage. If it is not doing 14 volts, get into all the connections of the charging circuit. After the years, several of these will develop enough corrosion to reduce the charging effort. Doesn't take much. Especially the plug behind the right have cover. These,, often, develop enough resistance to heat the plug material to the melting point. (Again, doesn't take much.) Resistance across the connectors must be, essentially, zilch! (Note that a charging current of 5 amps across a resistance of 0.5 ohm is good for a voltage drop of 2.5v. So, even 3 amps coming from the regulator thru 1 ohm is a 3 volt loss!)


One other quick check for your battery: After you have fully 'charged' it, put a volt meter across the terminals to read it when you start the bike. Should not read lower than 10 - 11 volts. If it drops far down the scale, bad battery. This is, obviously, a quick check to determine if the problem is battery or charging circuit. Either way, if you haven't cleaned and greased the charging circuit connectors within the past 5 years, I would definitely do that.
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Playtex11

Re: Low voltage and dying battery

Post by Playtex11 »

Thanks guys! Will attend to this tonight.

Playtex11

Re: Low voltage and dying battery

Post by Playtex11 »

Struck out. After trickle charge all night, battery showed 13v on outside voltmeter with just the key on. Cleaned and WD-40'ed all connections behind right side panel, none looked too bad and no evidence of anything melting. Gave 3 solid starts and battery dropped to 11.1 on all starts using an independent VM. Charge on bike VM @ 3000RPM was a hair less than 13 and 12.27 on the independent VM. It is back on the trickle charger. Voltage at shutdown was just a hair past 12v on the bike VM so the battery was running down.

So, I guess I have not found the problem and the battery is OK based on its cranking voltage. Sounds like it is ready for some shop time as I am not willing to try much more in my driveway.

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Re: Low voltage and dying battery

Post by desertrefugee »

Could be as simple as worn out brushes in the alternator. Three bolts to find out.
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Re: Low voltage and dying battery

Post by Larry Zimmer »

Yes, would appear the problem is with the charging system; not the battery. Good luck Hope it is relatively simple.
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Re: Low voltage and dying battery

Post by steve murdoch icoa #5322 »

I know the battery is not being charged at idle.
At what rpm does the charging system start working? Is it at 3000 rpm where Larry is asking for readings?

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Re: Low voltage and dying battery

Post by spencer »

At 3000 rpm, it should be charging. Next thing to check is probably the alternator brushes or the rectifier/regulator. I'm not sure which is easier to do. Someone will tell you which to do first. I don't have any experience doing that since I don't have a Honda alternator.
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Playtex11

Re: Low voltage and dying battery

Post by Playtex11 »

Per Larry's instructions, 3000 RPM was the setting I was using when reporting the volts on the bike meter and the independent meter. I apparently have the "Euro" alternator. Has 3 nuts holding the cover on. What bolts do I take out to check the brushes? I could do that as long as springs, ball bearings and tiny parts don't go flying in every direction when the bolts are removed. Where are the regulator/rectifier located?

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Re: Low voltage and dying battery

Post by tevan »

I still suspect the battery as your problem. I would charge it fully and take it somewhere for a load test. That is a easy one to check from square one.

Playtex11

Re: Low voltage and dying battery

Post by Playtex11 »

Tonight, I will substitute the battery with a fully charged known good battery and advise. Didn't get to that yesterday before running out of daylight. Thanks!

Playtex11

Re: Low voltage and dying battery

Post by Playtex11 »

Failure with changing to a known good, fully charged battery.

Voltages were near identical to the test I did yesterday with the independent VM. It won't show more than 12.03v at the battery terminals with throttle set on 3000 RPM. Gives good solid starts but at that output, it is just a matter of time until it runs down. Off to the shop seems to be the next step.

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Re: Low voltage and dying battery

Post by steve murdoch icoa #5322 »

Before you head to the shop have a look at this excellent thread from Ross on alternator maintenance.
Have you heard any of the "chirping" or oddball noises coming from the alternator area?
viewtopic.php?f=21&t=6781

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Re: Low voltage and dying battery

Post by wyly »

your battery may not have been at fault originally but once it's been discharged a few times it can become part of the problem by no longer holding a charge...

last summer my GS had a new battery but then fell victim to a cascade of problems, each bringing the next component down, problem started in the alternator, regulator rectifier... even after replacing the alternator and R&R the battery was compromised and I replaced that too :(
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

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