Battery voltage drop after fans turns ON

[himanshu23]

Hey all

This is my 2nd post regarding long unresolved issue I am facing in my 2011 Gen II hayabusa.

In my last post, regulator & rectifier unit is found to faulty as stator coupler is melted. Hence it was replaced along with new battery (YTZ14S).


last week I had noticed :

1. When engine is cranked battery is struggling to provide current. Ignition turned off and cranked again. Engine started. But I had a doubt.
2. While riding I had noticed that when Cooling Fans turns ON, horn pitch is reduced/down. Fans turns OFF everything OK. This repeated 5-7 times.
3. When I reached home I had immediately checked charging voltage which was around 13.2V when fans were OFF & High beam ON at IDLE condition.
4. When Fans turns ON voltage dropped to 12.5~12.9V but doesn't rise to 13.2V at Idle condition, engine need to be revved to reach 13.5V.
5. Lastly I wanted to check generator assy. as per manual resistance across terminal should be 0.2~0.7 ohm. but in my vehicle it is around 0.8~0.9 ohm.
6. On removal of stator 4 coils are more reddish than other.

please help me out I am fade up with time situation.

[Kiwi Rider]

@himanshu23 ....
Questions:
Did you fit OEM parts or aftermarket Chinese parts when you last replaced stator and reg/rect?
Did you replace the melted connector plug with good quality parts?
Did you check the magnets on the rotor for damage? ( ie cracking or insecurity?)
After installing new parts, did you check the AC voltage at all 3 phase wires of the stator (yellow wires) for around 20vAC at idle and around 70-80vAC each at 6000rpm?
Did you check continuity from the stator connector plug thru to the Voltage reg/rect connector plug?
Also, that yellow volt meter is a cheap one, ($3.70USD) and when getting down to 1 ohm or less, may very well be inaccurate so I suggest using a quality meter for accuracy.

[himanshu23]

@himanshu23 ....
Questions:
Did you fit OEM parts or aftermarket Chinese parts when you last replaced stator and reg/rect?
Did you replace the melted connector plug with good quality parts?
Did you check the magnets on the rotor for damage? ( ie cracking or insecurity?)
After installing new parts, did you check the AC voltage at all 3 phase wires of the stator (yellow wires) for around 20vAC at idle and around 70-80vAC each at 6000rpm?
Did you check continuity from the stator connector plug thru to the Voltage reg/rect connector plug?
Also, that yellow volt meter is a cheap one, ($3.70USD) and when getting down to 1 ohm or less, may very well be inaccurate so I suggest using a quality meter for accuracy.

Answer :
Stator is not replaced only connector (male/female) replaced with new one. Reg/rect is new OEM (suzuki)
Melted connector replaced
No damages on rotor assy.
55~65V at 5K rpm
Continuity not checked from stator connector plug to reg/rect.

will verify again with another multimeter.

[Kiwi Rider]

Answer :
Stator is not replaced only connector (male/female) replaced with new one. Reg/rect is new OEM (suzuki)
Melted connector replaced
No damages on rotor assy.
55~65V at 5K rpm
Continuity not checked from stator connector plug to reg/rect.

will verify again with another multimeter.

Is the stator output around 20v AC at idle?
Is the voltage reg/rect OEM or aftermarket?
I had an aftermarket reg/rect on my Busa and the voltage output was low, about the same as yours. I had slow starter motor cranking when engine at normal temp, and if I left the bike standing/parked for 2 weeks the battery went flat so I was always having to charge the battery (battery was near new).
I fitted a genuine Suzuki part (reg/rect) and it cured all my electrical charging system issues, it now charges at 13.8v at idle, and 14.6v while riding at 3800rpm (100kmh). I can leave it parked up for a month and it still starts instantly with good cranking speed from the starter motor.
Also, your bike's cooling fan is working a lot more than many of the members' bikes here, I'm assuming you're in India with high temps daily.... and the fan will run constantly, which is very demanding on the battery/charging system.
I'm in New Zealand and it's a temperate climate, even when sitting in traffic the fan only comes on if it's a warm day, like around 25degC.
In your country you will experience over 40degC regularly, correct?

[himanshu23]

Is the stator output around 20v AC at idle?
Is the voltage reg/rect OEM or aftermarket?
I had an aftermarket reg/rect on my Busa and the voltage output was low, about the same as yours. I had slow starter motor cranking when engine at normal temp, and if I left the bike standing/parked for 2 weeks the battery went flat so I was always having to charge the battery (battery was near new).
I fitted a genuine Suzuki part (reg/rect) and it cured all my electrical charging system issues, it now charges at 13.8v at idle, and 14.6v while riding at 3800rpm (100kmh). I can leave it parked up for a month and it still starts instantly with good cranking speed from the starter motor.
Also, your bike's cooling fan is working a lot more than many of the members' bikes here, I'm assuming you're in India with high temps daily.... and the fan will run constantly, which is very demanding on the battery/charging system.
I'm in New Zealand and it's a temperate climate, even when sitting in traffic the fan only comes on if it's a warm day, like around 25degC.
In your country you will experience over 40degC regularly, correct?

Yes I had changed reg/rect with OEM in Aug month this year along with new battery.

Yes in India temp. Is around 35~40 degree

Just need to know whether stator is ok or not

[Dopey]

Yes I had changed reg/rect with OEM in Aug month this year along with new battery.

Yes in India temp. Is around 35~40 degree

Just need to know whether stator is ok or not

So following the tests your doing is the only way to know for sure. Be sure to test each wire and make sure none of the have a short to ground as well. You definitely have an issue with at least one of the components and with the plug having melted it most likely put some extra wear on everything. Even with that being a cheaper meter like kiwi pointed out the stator is already testing at the end of its limits and over so with all your issues I'd be replacing the stator and rectifier if it was in my shop but I understand those are some expensive parts. Definitely go with an oem stator, the only rectifier I suggest my customers use aside from oem are the ones from "Ricks stator". I'm sure that's not what you were hoping to hear but that's your best bet to not end up stranded.

[himanshu23]

Hey all,



A update regarding the concern :



Exact issue : when engine is running cold charging voltage is maintained at 14.2V at idle, when engine reaches 100*C, both fans turn ON, it is clearly visible that headlight got dim and severe load on bike electrical system. Charging voltage drops to 12.5V. On disconnecting any of the fan coupler charging voltage is 13.5V.

I had checked Fan operation with hand both of them were operating freely. Dismantled motor no deris/dirt, carbon leads are also fine. Checked load operations : 3.86A through out running. Only during initial start it shoot upto 8A then maintained at 3.86A.

Checked fan relay : NO sulphation/oxidation, pristine condition of contacts. Relay checked for functioning working absolutely fine.

Checked : Wire short from generator coupler to rectifier coupler, no short to ground. Individual wire has continuity.



Please help me out what is the exact issue. I am frustrated all winter season is going on with rides.

[himanshu23]

Hello everyone

I am requesting everyone my help me out for this issue, what could be the possible cause and rectification !

[turbogsxr2025]

Hey was wondering if u ever figured out the problem currently having the same issue i know this post is 3 years old but thought I'd ask

I currently have a new mosfet regulator and brand new battery stator also reads 55 to 62 at 5k rpms on all pins once fans kick on jumps to 12.5 and bike would go into a missfire till fans shut off

[sixpack577]

Hey was wondering if u ever figured out the problem currently having the same issue i know this post is 3 years old but thought I'd ask

I currently have a new mosfet regulator and brand new battery stator also reads 55 to 62 at 5k rpms on all pins once fans kick on jumps to 12.5 and bike would go into a missfire till fans shut off

Did you replace the battery, stator, and regulator/rectifier because of this problem?
Oem parts?
Is this a basically stock bike, or the turbo in your screen name? I ask that because of aftermarket electronics with most turbo setups
Have you checked for a parasitic draw with the ignition turned off?

[Hayabusa Wannabe]

Welcome to the forum @turbogsxr2025.

[Bumblebee]

Could it be a bad relay or perhaps a bad fan motor?

[turbogsxr2025]

Did you replace the battery, stator, and regulator/rectifier because of this problem?
Oem parts?
Is this a basically stock bike, or the turbo in your screen name? I ask that because of aftermarket electronics with most turbo setups
Have you checked for a parasitic draw with the ignition turned off?

O wow sorry super late reply it is turbo its not a parasitic draw I can leave the bike off for weeks and itll start up without a battery tinder on . It's a new battery and a new msofet regulator from rmstators i didn't change the stator since it measures the 59volts on all three pins at 5k rpms unless once it gets hot starts to die but it mostly feels like the charging system cant keep up when the fans kicks on itll slowly drain dropping it below 12 volts but before the fans kicks on itll read 13.5v around there what I did notice is that when I start the bike up it takes a while for the volts to climb up from 12v not sure if its like a car that once it starts it shoots to 13.5+ volts

[turbogsxr2025]

Welcome to the forum @turbogsxr2025.

Thanks you

[turbogsxr2025]

Could it be a bad relay or perhaps a bad fan motor?

Hmmm ill have to check the fans then I dont think the relay might be a problem since its only when the fan kicks on but it hold nice at 13.5 with aftermarket fuel pump and oil scavange pump for the turbo only once it gets to temp and fans kicks on that the voltage starts to drop from there

[202mphbusa]

Unplug OEM fan power fused 12v to fan with a ground to see if it occurs if you bypass the OEM wiring

Maybe fan power wire has bad spot and harness shows voltage drop when OEM fan circuit draws.

[Dopey]

O wow sorry super late reply it is turbo its not a parasitic draw I can leave the bike off for weeks and itll start up without a battery tinder on . It's a new battery and a new msofet regulator from rmstators i didn't change the stator since it measures the 59volts on all three pins at 5k rpms unless once it gets hot starts to die but it mostly feels like the charging system cant keep up when the fans kicks on itll slowly drain dropping it below 12 volts but before the fans kicks on itll read 13.5v around there what I did notice is that when I start the bike up it takes a while for the volts to climb up from 12v not sure if its like a car that once it starts it shoots to 13.5+ volts

So the funny part is I had responded to this post years ago and just went thru this same issue myself. Bike said it was charging until fans came on them it would drop and go back up when they turned off. I tested things multiple times and the only thing that seemed wrong and it wasn't every time but when testing the stator only on a certain 2 wires I would have a different reading. I ended up replacing my stator with a very low mileage oem one because funds were low and charging system is back and better then ever. Was actually worried because at first it was reading 14.9/15.0 volts at the meter/ charge port but when I tested at the battery it was reading 1½-2 volts lower then the meter which has it charging at a steady 14.6 to 14.8 and suzuki says up to 15.5 is acceptable even tho I wouldn't accept it. Anyways sorry for rambling on but make sure you test every combination on your stator multiple times and I'm gonna say it's probaly gonna be your stator that's your issue. And you said you installed a mosfet rectifier did you order an actual shindengen rectifier kit or just a lot that claims to be mosfet? I have a couple websites that use for mosfet kits I install on bikes in my shop all the time and they are actual shindengen parts and work extremely well.

[Kiwi Rider]

So the funny part is I had responded to this post years ago and just went thru this same issue myself. Bike said it was charging until fans came on them it would drop and go back up when they turned off. I tested things multiple times and the only thing that seemed wrong and it wasn't every time but when testing the stator only on a certain 2 wires I would have a different reading. I ended up replacing my stator with a very low mileage oem one because funds were low and charging system is back and better then ever. Was actually worried because at first it was reading 14.9/15.0 volts at the meter/ charge port but when I tested at the battery it was reading 1½-2 volts lower then the meter which has it charging at a steady 14.6 to 14.8 and suzuki says up to 15.5 is acceptable even tho I wouldn't accept it. Anyways sorry for rambling on but make sure you test every combination on your stator multiple times and I'm gonna say it's probaly gonna be your stator that's your issue. And you said you installed a mosfet rectifier did you order an actual shindengen rectifier kit or just a lot that claims to be mosfet? I have a couple websites that use for mosfet kits I install on bikes in my shop all the time and they are actual shindengen parts and work extremely well.

As usual you are bang on, my friend!
I also would fit a new OEM stator and it’s interesting what you said about the ‘mosfet’ regulators… that some are sold claiming to be the mosfet type, when they’re actually not, but are fake.
The Chinese cheap reg/rect tend to overcharge (15v ish) and overheat and burn out in short order.
Moral of the story.. use known quality parts!