Voltage for battery

[ofblong]

Ok my battery keeps dieng and I am assuming its because its an old battery. Anywho I checked the voltage at idle and the system shows 11.2 volts and then when I rev it it jumps up to 12.7 volts. I am assuming this means the charging system is good and that I should just replace the battery? Its a 1997 Honda Shadow Deluxe VLX.

Thanks for those looking and why does it seem like everytime I notice someone has a problem with their bike and I read the thread I end up having that problem?????

[jonnythan]

Ok my battery keeps dieng and I am assuming its because its an old battery. Anywho I checked the voltage at idle and the system shows 11.2 volts and then when I rev it it jumps up to 12.7 volts. I am assuming this means the charging system is good and that I should just replace the battery? Its a 1997 Honda Shadow Deluxe VLX.

Thanks for those looking and why does it seem like everytime I notice someone has a problem with their bike and I read the thread I end up having that problem?????

This means your charging system is *not* good.

You should be seeing at least 13.5 V when revving the engine.

Go here and find the problem:
http://www.electrosport.com/Images/fault_finding.pdf

[ofblong]

if the battery isnt fully charged could that be causing me to only see 12.7v when revving?

I should mention that what baffles me is all I need to do is jump it with a car battery (just touching the cables to my battery after connecting to my vans battery) it starts right up no problems. Also while riding down the road revving the engine gives me no increase in light output from the lights and slowing down doesnt change it either....

[jonnythan]

if the battery isnt fully charged could that be causing me to only see 12.7v when revving?

I should mention that what baffles me is all I need to do is jump it with a car battery (just touching the cables to my battery after connecting to my vans battery) it starts right up no problems. Also while riding down the road revving the engine gives me no increase in light output from the lights and slowing down doesnt change it either....

Shouldn't, nope. I've had a battery that was so dead it couldn't turn the starter after spending the night on the charger show 13.7V at idle.

That is kinda odd. It's entirely possible that the charging system is providing just enough current to power the electronics and maintain 12-12.7 volts while moving, but not enough to charge the battery, I guess.

[ofblong]

if the battery isnt fully charged could that be causing me to only see 12.7v when revving?

Shouldn't, nope. I've had a battery that was so dead it couldn't turn the starter after spending the night on the charger show 13.7V at idle.

hmm ok . thanks for the link I was trying to find it earlier though I found it just now

*edit a loose wire on the liscence plate light wouldnt cause this would it?

[ofblong]

hmm if it was the charging system itself why would I be able to jump start the bike ride to work which is 12 miles and still have the bike start after I get out of work?

[Sev]

Hokay...

so...

it's not unusual for older bikes to be in a state of discharge at idle. Simply the alternators were not powerful enough to charge the battery at idle. This does not mean your charging system is damaged or pooched. However based upon the year of your bike it does sound like there is some loss across the system. I would suspect a corroded connection somewhere.

Second... you revved, but you didn't say to what. Typically speaking the manual's will tell you to rev to 5000rpm (as this is a rough standard) and in that range you should be seeing anywhere from 13.5-15 volts charging. Depending on what bike.

The fact that your battery is losing power could be one of two things:

1) The battery is cooked
2) The charging system is weak

A cooked battery can make the charging system APPEAR weak. Because it has an innate resistance that will be picked up when you check the charge across the terminals.


If you have a full charge on the battery will the bike start?

If you let the bike sit overnight or for a couple of days does the battery discharge?

If you answered yes to both of those replace the battery. If not... you're going to have to troubleshoot your charging system. I think I've posted the steps a couple of times, I'll try to track them down again and repost them.

[ofblong]

Hokay...

so...

it's not unusual for older bikes to be in a state of discharge at idle. Simply the alternators were not powerful enough to charge the battery at idle. This does not mean your charging system is damaged or pooched. However based upon the year of your bike it does sound like there is some loss across the system. I would suspect a corroded connection somewhere.

Second... you revved, but you didn't say to what. Typically speaking the manual's will tell you to rev to 5000rpm (as this is a rough standard) and in that range you should be seeing anywhere from 13.5-15 volts charging. Depending on what bike.

The fact that your battery is losing power could be one of two things:

1) The battery is cooked
2) The charging system is weak

A cooked battery can make the charging system APPEAR weak. Because it has an innate resistance that will be picked up when you check the charge across the terminals.


If you have a full charge on the battery will the bike start?

If you let the bike sit overnight or for a couple of days does the battery discharge?

If you answered yes to both of those replace the battery. If not... you're going to have to troubleshoot your charging system. I think I've posted the steps a couple of times, I'll try to track them down again and repost them.

I can say yes to the first ? but the second ? I know i let it sit for a couple days. The bike started and then oh 3 minutes later it stalled and I couldnt start it back up until I jumped the battery.... Overnight It doesnt as I charged the battery 2 days ago and today it started I rode to the gas station which is a mile away and filled the bike. After filling it wouldnt start. Also thanks for clarifying about the resistance making it appear like the charging system. I think I will buy a new battery anyways as I have no idea how old the battery is since I bought it used last year. This bike is kinda making me wish I would have spent the extra 3 grand and bought a brand new Multistrada 620 lol. I will also say that I rode from the gas station (after getting jumped) to work. I let it sit for 4 hours now. I went out and the bike started right up. So I am guessing its the battery iteself.

After I charge the new battery, I am assuming they dont come fully charged when brand new, I should then check the voltage across the battery terminals again and make sure it is jumping up to 13.5ish? I cant say what RPM I was running it at since I dont have an RPM gauge but I opened the throttle about 1/2 way. Kind of makes me nervous to open it all the way when idle though I am sure it wont do any more damage than if I was actually moving?

[Sev]

1/2 Throttle won't hurt the bike, just don't hold it there. Keep it open long enough to get a reliable reading, then close it back up.

All a volt meter does is measure the difference in voltage across two points. So if there is a drain at any point (ie a bad cell in the battery) then your charging system will read lower then it should. How... in depth are you willing to check your charging system?

Sorry, I forgot about this thread.
You need one of these


Okay, get the bike running then set your multimeter to...
20 volts DC, measure the voltage across the battery at idle. It should be just below or just above 12.8 volts.

Rev it up to 5000rpm and take the same reading. It should be closer to 14 or 15 volts.

If it isn't there is a problem with your charging system. Lets try to find it.

set the multimeter to something in the range of 200 volts AC

Find the three yellow wires coming out of your alternator.

Follow them back to the connector. Disconnect the connector and measure the AC voltage between the wires at 5000rpm. You'll need a friend to rev it up for you. Think of the three wires as A,B,C

Do:
AB
BC
CA

Each should be in the range of 60-80 volts if memory serves. But your manual will have better stats. If one is substantially lower you may have a bad coil.

Turn the bike off and switch your multimeter too the ohmmeter. The higher the reading the better. Now stick the positive lead into one of the yellow wires and touch the negative to the frame. There should be infinite resistance or no continuity. Test the other two wires in a similar matter. If you get continuity then you've got a bad coil and need a new stator.

If the alternator output is good, then you need to check your connections to the regulator/rectifier. If the connections are good going TO the reg/rect and if they're good from the reg/rect to the battery, then you need to replace the reg/rect.

It's fairly simple once you get things broken down into little portions/sections.

Yes, you need to charge the new battery no matter what the shop tells you. Make sure it has a good charge on it, then let it sit for 30 minutes. Install and crank the bike over.

Check the idle charging and charging at 5grand. If they aren't good... then you'll need to run the above checks to find out what is wrong.

[slimcolo]

I have seen some batteries quit working simply because they are dry. A system that overcharges can boil a battery (probably not the problem but something that is often overlooked during maintainance) Also check for corroded/loose connections.

It is also possible to get a good voltage reading but still be under in amps. (most ampmeters do not go high enough) BT alternators are 14,22,32 and 40 amps.

It would help to know what bike and charging system you have. Make, model, alternator, generator,mag.

Most manuals state that the first thing when trouble shooting electrical systems, Make sure battery is good and has full charge. Then follow Sev's instructions in last post, unless your bike (see manual) has some model specific instructions. (some bikes have a fuseable link that needs to be bypassed for testing)