MV Agusta Forum banner

Battery light

6K views 58 replies 9 participants last post by  tallguyjc 
#1 ·
Ive noticed when riding that every now and then my battery light on the instrument cluster will come on. It will stay on for a few minutes at most then go off. Normally this happens just after I've been at a traffic light for a decent amount of time. Is this anything to be worried about and should I be startibg to price an alternator, or is this something that happens with the first gen Brutale? Thanks guys.
 
#3 ·
That light should not come on. Period. When it does you are being told the charge rate to the battery is low.

Check your battery cables and terminals, especially ground cable and attachment at the engine. Check connections from alternator to the battery/starter relay/main fuse.

It's intermittent, I would not suspect the alternator itself.
 
#4 ·
Ok, so I check all the connections,the other and everything looked good. Buttoned it back up and away I went. So today I replaced the rear turn signals and front tire. But the bulb for the license plate light broke so I rode to get a new one. The battery light stayed on for the trip and was on on the way home. It had nevwr stayed on for that long beofre. I got the new bulb in and went to start it and nothing. Battery was dead. Hooked up a tender to it and let it charge for a bit and it started again but then the instrument cluster lit up everything, and flashed so I shut it down. Now when trying to start it the battery makes a fast clicking sound. So hooked my brothers battery to it and it fired right up, but the battery light remained on, and his volts dropped to 10 and we killed it. Does this just sound like a dead battery like I'm hoping it is, or something to do with the alternator? I hope it is nothing expensive or complex as this is my only means of transportation.
 
#5 ·
Although your battery may now be shot (from repeated excessive discharge), your problem is not a bad battery.

Like with a car, one can start a bike with a bad battery with jumper cables, remove the cables and run it normally - as long as the alternator is charging correctly.

The ‘battery’ light is perhaps a bit of a misnomer, and should rather be called an ‘alternator’ or ‘charge’ light. It does not indicate the condition of the battery, but rather the condition of the current being generated by the alternator.
 
#6 ·
Exactly the same conclusion I came to reluctantly. Gonna pull the alternator off tomorrow and hope I can find a replacement for it on a Sunday. I've read to take the tank off, then the starter, remove some wires, then I should have access to remove it. I was really fearing that it was the alternator, and I am not looking forward to it.
 
#7 ·
Hi, when the light it's intermittent is a signal of coming bad alternator. So now is intermittent after few days or weeks will become fix light and yuor bike will not run or will stop (if battery it's totally died cause not recharged). First control how many volt is given the alternator and you'll understand if have some problem.
If you need an used alternator in good condition let me know
 
#9 ·
Misty5, I'm thinking I'll end up having to get an alternator from a forum member. I'll let you know for sure once Ibget it out. Where are ypu located at? I am sure they are not cheap to ship. And you're more,than welcome to PM me a price if you've got one. Thanks.
 
#10 ·
Okay folks, I am going to throw a booger in the pudding. There are several things that can cause a poor charge condition to show up. ONe of those things is a high resistive load in the circuit...i.e. a toasted battery. Another is poor connections at the star solenoid....which is a known problem with these bikes...yet another is poor grounds.

What I am saying here is to check your system before you go throwing the baby out with the bathwater. The alternator on these bikes is robust.

Yes, it could be a bad alternator, or more likely voltage regulator, but, without checking the simple things, you could just be burning good money.

Test your circuit. Check your connections.
 
#11 · (Edited)
The first gen Brutale (and F4) uses a Denso alternator....just like those found on small cars !! It can be repaired by any auto electrical shop. Just kind of hard to get off and on the engine.

But as SilentService said, they rarely fail More often it is the charging connections going toward the battery. The "Charge Light" is simply saying voltage has dropped below normal. That is, charge voltage/amperage is not reaching the battery.

Japanese bikes (older Honda in particular) are famous for melting the 3 wire connector between the alternator output and the rectifier. Enough so that several companies offer repair kits for this connector.

On your MV, where the rectifier/regulator are enclosed in the alternator case, this connection is the one at the starter relay.

Your battery may recover if you charge it with a "Smart" charger. Discharge alone doesn't ruin a battery, sitting in a discharged state for any length of time does.
 
#19 ·
Only thing between the alternator and battery are wires and connectors....That is it. Period. No switches, relays or computers.
 
#21 ·
@tallguyjc: What was the last thing done to the bike BEFORE the intermittent battery light?

Is the battery original equipment?
 
#22 ·
The bike is a 2005 750S. The last thing I did before,everything went south is changed the stock rear turn signals, the original ones were broken when I bought the bike...they were held on by tape. So I did that, and put a new front tire on at the same time. The ride was to go over to the auto parts store as to get a new light for the light that is above the license plate as it had burned out. The battery light came on as soon as I left and I thought it would go off in a minute or two as it always does, and it didn't. Got to the store, got the new bulb, and went home again with the battery light on the whole way. Got to the house and shut the bike down, then started checking the battery with a volt meter, and it was low. Hooked up a battery tender to charge it, and after that started the bike again with the meter connected. Watched,the battery drain to 8 volts where everything on the dash flashed, then the dash went blank, not even reading the rpms. Hooked my brothers battery up to the bike, and the same thing so we jumped to the alternator as the source of the problem.
 
#39 ·
The bike is a 2005 750S. T

Would you please put this little tidbit in your signature line? It sucks having to go back and try to figure out what friggin bike I am trying to diagnose remotely.

It will help us help you.
 
#23 · (Edited)
Well...you are definitely experiencing no charge to the battery. Even with a crap battery the bike should generate enough voltage to run....i.e.: you should see over 12V at the battery terminals.

So time to examine what's between the alternator and the battery. The alternator is an excited field type, so it needs battery voltage input to generate output. Not a permanent magnet type as found on most current motorcycles. It is a car alternator.

If there is low voltage due to resistance on the input side there will be low to no output.
 
  • Like
Reactions: theknurl
#24 ·
?

tallguyjc;
Listen to Ed
Pull the 4 wire plug next to the starter solenoid and check for corrosion
Check all the battery cables for corrosion this includes engine grounds
When everything is clean and coated with dielectric grease

With a multimeter on DC volts connect to alternator output and battery ground
You should see 14.5+ volts at idle

If not take your alternator to an automotive electrical shop.....it's either the diode plate or the regulator
Remove the starter 1st when removing the alternator

:wink2:
 
#26 ·
Ok, so I took the alternator to a shop this past week, they said it worked great and didn't see an issue with it at all. So we (my brother and I) reinstalled the alternator, and hooked everything back up, all of the connections look great, we live in a very dry area so not much moisture here for corrosion. We replaced the battery, and it fired up again, but the light was still on. When I connect the volt meter to the positive that goes to the battery and to the negative, it is only putting about .500 volts out. I believe this would be what is the brushes part the alternator, but I'm not an expert by any means. I really donw want to have to take the alternwtor out again, it was a huge pain to do.
 
#27 ·
Please put your bike model and year in your signature line!

Or put your bike model and year in EVERY POST asking for help.:thewife: This will save those of us who want to help you much time and aggravation.

Now, what was the voltage of the battery that you installed? Is it installed with correct polarity? The wiring to your signals: is it properly grounded? Did you disconnect the battery when doing the wiring work?

Did you reconnect ALL OF THE WIRES to the correct terminals on your battery?

These are just some of the things that could be causing your problem. If you took your alternator to a qualifies, quality shop, and they determined the alternator is working fine, then the problem is NOT your alternator..
 
#28 ·
I'll try to get the bike in my signature, I do this all from my phone and some of the CP options are lacking on the mobile version. But it is a 2005 Brtuale 750. For the turn signals, I didn't have the battery unhooked, I used the stock wiring though and used an electrical fitting to connect the wires, then used electrical tape to cover each connection individually. The battery ia a 12 Volt, and all is hooked up correctly with it. I did take the alternator to a shop that has a good reputation, however they do not deal with smaller alternator hardly ever. They are a semi truck alternator and battery service shop. They did have aomw reseevationa about it, but after looking it over thought they could do it. I don't understand why the alternator would only put out .500 volts on the output to the positive in the battery. The 40V fuse is also good, I've checked it 3 or 4 times though this ordeal.
 
#29 ·
If your resting battery voltage is 12VDC, tehn the battery is not charged fully or it is faulty. DC batteries put out 2.2 VDC per cell; therefore, your battery should be close to 13.4 VDC when in good condition and charged.

As for checking fuses...you used a meter on resistance, right? And got a reading near zero ohms....?

There are two fuses in the charge circuit holder...one is a spare and is not in the circuit. Make certain you checked the fuse that is in the circuit.

It is difficult to judge how competent someone is with a meter. There are many complications to incorrect or correct readings.
 
#30 ·
40 Amp fuse.... OK, if the truck electrical shop said it was OK you have to ask how did they test it. There are brushes and slip rings for the excited field, but these things rarely wear out at low mileage (it is an automotive alternator!!).

There is also a diode array to convert the AC to DC and an IC regulator that controls current to the brushes, raising and lowering the strength of the field to regulate output.

So, there has to be battery voltage supplied to the alternator for the field to excite and generate the output charge voltage in the stator.

The shop should have tested resistance and insulation of the stator and the field, the continuity of the brushes, and the diode array. The IC regulator can't really be tested easily without specialized equipment, but I would think the truck electrical shop would have that. Then again, trucks have larger charging systems and some run 24 volts.....so I don't know.

The connector at the solenoid where all the charge system connects gets hot and melts due to resistance developed from loose connections, which start an electrical corrosive process not really related to rust.

If all your wiring is good, clean and continuous then you could have a failed component in the alternator....and an automotive electrical specialist should be able to repair it.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top