Topic: Alt. not bad. draining battery with just the key on

[78 k550]

Hey All,
I changed out the Alt. even though it was pushing out 1.0 ohm. I talked to Tim and did a AC voltage check it checked out ok so he said it was good. maybe figured it was something else in the Alt. didnt take his knowledge and blew 35 on an Alt. It is still doing something. I was sitting there after I got home and watching the meter with the key in the on position. no lights and the volts just drop lower and lower. This is with the meter across the battery terminals. So it looks like I have a defenate short. Look's like I something to do tomorrow. LOL

Paul

[oldbiker]

The moment you turn on the ignition key, there is a drain of about 2-3 amps from your battery (this is via the alternator field coil). If the voltage measured at the battery  can be seen to be dropping visibly then the battery itself is VERY suspect. It could be because the battery is not very well charged BUT it could also be because one or more cells of the battery have a high internal resistance. The cure for the first is obvious, a good 24 hr charge, but the cure for the second is a new battery.

[Steve F]

Don't forget that you may also have the ignition coil(s) drawing current as well.  Unless you remove the black/white wires on the coils or maybe turn off the kill switch, you're going to see a voltage drop.

[Super Sport 550]

In addition, the neutral light is probably on in addition to the oil pressure light. All of those things will add up to make the voltage drop with the key on.

As noted in a previous response, if the voltage continues to fall while you are watching it as you said in your post, you probably have a bad battery.

[78 k550]

Battery was bought 3 days ago. I'll charge it up and see what happens. I can run the bike and watch the volts drop with just the key in the on position. If the key is on it will slowly and I can see it dropping volts. If I turn the key off the battery will go back up to 11.5-12 volts. I'm going to start checking for a bad wire. Or the ignition switch went south.

Paul

[oldbiker]

Since your battery is new, I bet you bought it dry charged. Although they call it charged it still pays to charge fully and then check the specific gravity of the electrolyte. It should be 1.270 if the battery is properly charged

[SteveD CB500F]

Just cos it's new, doesn't mean it's OK...

My son had a brand new battery in his Ford Fiesta fail after only 2 days.  It would charge up fine to the correct voltage and then drop like a stone as soon as any load was placed on it.

The supplier replaced it without a murmer (so it must happen fairly often eh?)

[crazypj]

No load volts of a good new battery, when fully charged will be closer to 13.5V.
If its a sealed battery you can quick charge it for 1~2 hr. at max amps The Specific gravity of sealed battery acid is 1.30~1.32.  If conventional, leave it on 1/10 of capacity for 24hrs (12Amp hour=1.2 amps, charger on 2 amp setting will be close enough)
If your worried about charging, get a cheap Ammeter (Amp Meter) from any auto shop and check charge rate, voltage isnt really a good indication of charge (put it in series with red wire from starter relay to fuse box or main feed to ignition,  NOT  the heavy wire from battery) If you try and charge battery on bike by running it you may burn out all of the charging system, it wasnt designed to put out max amps for extended periods ( had lots of trouble with 'old' Suzuki's, even when they were new )
AAAAH, the good old days of Joe Lucas, Prince of Darkness