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Discussion Starter · #1 ·
So my battery is dead, or so I thought. It wouldn't start and when I jumped it, it idled really low, like 850-900rpm. I stopped by my local stealership with the battery, and they tested it, said it needed to be charged. I left it over night and picked it up today. They said they load tested it and it was fine after the charge.

Put it back in my bike, and started the bike. Started fine. I put a meter on the battery and it showed 14.1v. Just like it should, and the bike idled normally. As it idled, I watched the volts drop down into the mid-11s and the rpms dropped back down into the 850-900 range, and the headlight dimmed. If I rev the bike, the headlight brightens up and the volts will slowly climb back up to the 14v range. As soon as I let it go back down to idle, the volts start falling off again.

Battery or alternator? My warranty runs out in a couple weeks, so I want to get it figured out, fast.


Dave
 

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Idle speed readings aren't necessarily the right speed to check for charging at.... what's it look like at 1500 RPM? Is this the origional battery?

My thought would be to start the bike, then disconnect the battery. The alternator should be putting out enough juice to run the bike all day, without the battery. If it dies when you disconect the battery (and you cannot 'steal' juice from it)... the charging system, isn't. If it runs normally, that should isolate the problem to the battery.
 

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Discussion Starter · #3 ·
Started the bike, then disconnected the negative battery lead. The bike continued to run, however, it did so very rough, the lights were very dim, even flickering, and the idle revs dropped down into the low 800s. Also, while idling without the battery attached, the bike was generating 8.5v or so. If I rev the bike, it goes up to the 12.5v range, but drops back down as soon as you let off the throttle.

Comments?

Dave
 

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If it were a 70's bike the disconnecting the battery trick would sound like a good idea, but I would hesitate to trust it for a modern machine. In fact, the other way round, a healthy battery should be able to keep the engine running even when the alternator is bad. So really, we know little about what goes on.

What you describe can have many reasons. A bad connection or a short somewhere, the regulator, alternator, ignition coils, efi,... Does the warranty put the burden of diagnosing the problem on the owner?
 

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The Flying Finn
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+1 to the above post, disconnecting the battery and running on alternator alone is a quick way to kill an alternator. A bad alternator can kill a battery, and a bad battery can kill an alternator.

Take the thing to the dealer and let them diagnose it, as soon as the problem is registered, it can take months for them to finally get it right, it will still be covered under warranty, so get the thing into them!

As far as checking volts at idle, this is an engine designed to run up to 14000 rpm. It's not supposed to put out max charging power until roughly 7000 rpm or so, so I'm not surprised that it only put out 8.5 volts at idle.
 

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Can anyone verify that they get 14 volts at idle?

I had the same problem. I did a lot of slow parking lot riding at the start of last season to get used to tight turns, etc. After I stopped my bike, it wouldn't turn on anymore.

I was only getting 14 volts when the RPMs are above 2,000 or 2,500. I don't know the exact details of how voltage regulators work, but I believe this is normal operation.

If your battery is old and can't hold a charge very well (i.e. if it has problems starting after sitting for a week or two) then you should probably buy a new battery.

regarding the 800-900 rpm range, bumping that up to 1200 will make the bike a run a bit smoother.
 

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if you want a good long lasting battery, skip the internet mythology and dont use a battery tender either. but you obviously have an alternator problem.



 

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What are you saying about not to use a battery tender...... Did you know if the chemicals inside of a battery stop reacting they die..... There for the tender keeps a very very low charge if you will, even though its not a charge at all.... When using a battery tender you will keep the batter alive not kill it or harm it in anyway. First winter with my bike no tender battery went dead... Second year tender battery is still strong. Orig. battery. I leave bike hooked up and tender in bc your ECU will always use small amount of power with modern bikes. I will also add the the chemicals inside the batter react to different temp. as well. Buddy of mine does not use tender but keeps his bike around 45 degress in the winter. He has never had a dead battery. My garage is as cold inside as outside.
 

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The Flying Finn
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I had the same problem. I did a lot of slow parking lot riding at the start of last season to get used to tight turns, etc. After I stopped my bike, it wouldn't turn on anymore.
Taking my M2 exit course, the first half day was all slow parking lot stuff. Never got above 3500 rpm or out of first gear. Went to start up the bike after lunch and she was dead! Bump started down a hill, went for a 15 minute blast up the highway keeping the revs over 8000 and I never had an issue with that battery again (had the bike for another 1.5 years after that).

I left my bike for months at a time with no tender, and she'd always start right up.
 

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Started the bike, then disconnected the negative battery lead. The bike continued to run, however, it did so very rough, the lights were very dim, even flickering, and the idle revs dropped down into the low 800s. Also, while idling without the battery attached, the bike was generating 8.5v or so. If I rev the bike, it goes up to the 12.5v range, but drops back down as soon as you let off the throttle.

Comments?

Dave
Above 1500 RPM, the alternator/charging system should be delivering 14 volts and change anywhere on the system you measure it.... doesn't sound like that's the case.

As someone else suggested, get it in, and get the issue logged.... it's not so simple to ID which part is failing on the charging side. Could be the regulator/rectifier, or the alternator itself, or a short, or a corroded contact.

Given the dealership load tested the battery and it charged properly, it's fair to say it's not the primary culprit.
 

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I've had the battery die on me from just idling and running around at very low rpms <3k (the first day i got it was just riding up and down the alley way getting familiar) it eventually got low enough it couldn't start the bike. Got it jumped, and rode it above 5k for 20 minutes and havn't had a problem since...

+1 to the battery NOT charging at idle.
 

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ped,

If you are asking that of me.... yes, I saw your photo. It's a clear indication that your charging system is running correctly as low as 1320 RPM. (with whatever instrument error exists in the Tach.... I have my idle set up to about that speed, to ensure the charging system is always working.)

Less than 14 VDC indicated would not necessarily indicate a fault with the alternator.... certainly, with the charging system; but there's not enough info from that one measurement to state 'faulty alternator' as an absolute fact. If one leg of the bridge rectifier let go, you'd get a lower DC reading on a DMM, but that would not show all the ripple. Part of the alternator's output would not be converted from AC to DC.

From there you can jump on the alternator -- and 'potentially' be right. Or wrong.

A high resistance between contacts on some point in the wiring could screw up the voltage regulator.... it may 'see' some lower value as correct, and regulate at less than the desired 14. something. If the leads going to the battery are corroded, the voltage supplied is divided between the network, and you may end up with a situation that the battery never recieves enough voltage to force energy into it.

It's a good idea at this point to put the thing in the shop, and let the warranty people take a look.
 

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Volts != Current

Sure you can be generating 14volts at idle, but not enough current to properly charge it.
 

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What are you saying about not to use a battery tender...... Did you know if the chemicals inside of a battery stop reacting they die..... There for the tender keeps a very very low charge if you will, even though its not a charge at all.... When using a battery tender you will keep the batter alive not kill it or harm it in anyway. First winter with my bike no tender battery went dead... Second year tender battery is still strong. Orig. battery. I leave bike hooked up and tender in bc your ECU will always use small amount of power with modern bikes. I will also add the the chemicals inside the batter react to different temp. as well. Buddy of mine does not use tender but keeps his bike around 45 degress in the winter. He has never had a dead battery. My garage is as cold inside as outside.
I still have the original battery in my FZ6. It is five years old and has never been on a battery tender. Before my current job the FZ6 could sit for two months at a time and never have a problem. My garage is not heated either.

Why would the ECU use any power when the bike is shut off? Now the clock is another matter and if you are in Europe, the immobilizer will draw power when the engine is switched off.
 

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the bike charges at idle, period. if the guys battery wont hold a charge its either because he used a tender or he's been running off the battery and its drained it so bad that it wont hold a charge. all thats needed is to hook up a volt meter while its running and see if its putting out the correct voltage. if not theres something wrong with the stator or the regulator.
theres no reason a battery shouldnt be lasting 6-8 years min. thats why i laugh at the 10,000 threads of a bad battery every spring. people will insist on using a tender and then scratch their head why they only get 2 years of battery life. if you really dont want to start the bike over the winter and the battery actually loses enough charge to not crank, THEN put it on a charger for an hour and you'll have batteries lasting you a long time. and especially with AGM batteries they dont lose charge like lead batteries.
its simple the stator is made to put out max capacity above about 900 rpms, any more the regulator blows off. that keeps the load on the engine consitant. if you're not getting 14+ volts at the manuals set idle range you have problems.
 

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The Flying Finn
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its simple the stator is made to put out max capacity above about 900 rpms, any more the regulator blows off. that keeps the load on the engine consitant. if you're not getting 14+ volts at the manuals set idle range you have problems.
Why would a manufacturer spec alternator output wattage at X rpm then? (usually around 7000 rpm)

Why would my, and others, battery have died when running at low RPM in the heat with the fan on, if my alt was putting out max at 900 rpm?

I think the bottom line to the OP is this, GET THE THING TO A DEALER NOW!!! :cheers

I agree with not having to use a battery tender though. I live in the great white north and use my lawn tractor as a plow, and it doesn't need any type of tender in the winter, and in the long gap between seasons there's also no issue. Not yet anyway!?! :D
 

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I live in the great white north and use my lawn tractor as a plow, and it doesn't need any type of tender in the winter, and in the long gap between seasons there's also no issue. Not yet anyway!?! :D
+1, my bike sits in my basement from november to april and it starts up fine, no charger, tender, whatever, mind you my battery isn't so old, we'll see if it lasts 6-8 years. hopefully haha
 
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