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What's the voltage?


dan cata

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Hi all,

 

I have done the abs relay mod yesterday so that it will not throw errors if the battery is weak. All is good now, or at least as I can test it since my bike is indoors.

 

Just for my knowledge, what's the voltage across the battery leads that the ABS starts to not work? 10V? 9V?

 

Dan.

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Here's a good article on the subject, but it does not specifically mention the threshold voltage, other than to say the threshold may be too high:

 

ABS faults

 

I would think that the ABS fault threshold is probably around 11 to 12 volts, but don't know for sure. I do know that when I did the modification on my bike, it faulted every time I started the bike, even on a daily basis in the summer. After the modifcation, it did not fault once in 30 months, even when the battery was clearly in need of replacment (had to be kept on life support).

 

In other words, the battery voltage is taken out of the equation by the modification. It simply waits until the alternator has signaled that it has come up to speed before beginning the initialization of the ABS.

 

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Hi all,

 

I have done the abs relay mod yesterday so that it will not throw errors if the battery is weak. All is good now, or at least as I can test it since my bike is indoors.

 

Just for my knowledge, what's the voltage across the battery leads that the ABS starts to not work? 10V? 9V?

 

Dan.

 

Afternoon Dan

 

Seeing as the ABS motor cycle on ABS pre ride initiation is the straw that finally allows the system to not initialize no way to know for sure what the actual threshold voltage is. When I have observed the failure with a voltmeter on the battery (not the system green wire as that would be lower) it seems to trip an ABS shut down in the 9-9.5 volt range but keep in mind the actual system voltage at the ABS input would be slightly lower.

 

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Danny caddyshack Noonan

Dan,

I haven't measured voltage BUT, can verify the following:

On startup, if the revs don't go over about 1300, give or take, the relay won't trip and initilaze the ABS. Once the ABS is initialized, is doesn't de-initialize unles the engine is shut off.

It is entirely within the realm of possiblity that this is a variable characteristic between different alternators and relays.

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Afternoon Peter

 

You are correct the relay pull in point is variable between different relays used and different alternators.

 

That is because the alternator circuit you are using to operate that relay is not meant to be a real output circuit, it is biased inside the voltage regulator to offset the charging light load (simply meant to turn the charging light off) . By using the alternator charging light circuit the relay voltage trigger point is heavily biased by the relay pull in coil resistance as well as the back feed current feeding back through the dash warning light circuit (light bulb resistance).

 

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Dan,

I haven't measured voltage BUT, can verify the following:

On startup, if the revs don't go over about 1300, give or take, the relay won't trip and initilaze the ABS. Once the ABS is initialized, is doesn't de-initialize unles the engine is shut off.

It is entirely within the realm of possiblity that this is a variable characteristic between different alternators and relays.

 

Hi Peter,

 

Yes, I now know how it all works and how the relay that I mounted does the job, but I was just curious if anyone knew the real level of batery discharge that the ABS starts to not work.

 

The way that I now see tings is that if I get the charging light ON on the dashboard, the ABS will start to not work again. That could be due to:

 

-alternator belt breaking while riding

-the charging relay inside the alternator going bad

-the alternator getting burned.

 

All of the above are very likely to NOT happen.

 

So, so far we have 9.5 V. Anyone else? :)

 

Dan.

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Morning Dan

 

You are correct (IF) your charging light comes on that means the alternator has stopped supplying current to that circuit (for any of the reasons you mentioned). That also means your added ABS relay would open and deactivate the ABS. Under those conditions (alternator quitting) it really doesn’t matter at what voltage the ABS goes into a failure as the with the relay open you would have “0” volts to the ABS and that will deactivate the ABS regardless of the voltage threshold.

 

You could add a simple switch across the relay to by-pass the relay contacts if your alternator quits but if your charging system quits on you you probably don’t want the ABS energizing anyhow as that ABS shaft motor takes a lot of current to run so would pull an already marginal system voltage even lower the minute it runs. (probably better off without the ABS active with a failed alternator).

 

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Clive Liddell

So, so far we have 9.5 V. Anyone else?

 

===

I don't think it's an absolute voltage that causes ABS faulting. I have had faulting on startup after a 20 minute run. I am sure that it is the DROP in (battery) voltage on starting that is sensed and faults the ABS.

 

Often, waiting about 10 to 15 seconds after ignition key on and before starting will result in successful ABS set with even a doubtful battery because the voltage will have stabilised albeit at a lower absolute value.

 

Anyway I went the route of fitting "push to open" switches and have had easy resets since then. The switch method also keeps one informed of the state of the battery :)

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So, so far we have 9.5 V. Anyone else?

 

===

I don't think it's an absolute voltage that causes ABS faulting. I have had faulting on startup after a 20 minute run. I am sure that it is the DROP in (battery) voltage on starting that is sensed and faults the ABS.

 

That's what I am saying, if the voltage drops below a certain limit, the ABS fails, no matter if it's on engine startup (most common) or while riding, like it happened to you (rarely)

 

Often, waiting about 10 to 15 seconds after ignition key on and before starting will result in successful ABS set with even a doubtful battery because the voltage will have stabilised albeit at a lower absolute value.

I guess I won't be able to test that now that I have the relay mod done :D

 

Anyway I went the route of fitting "push to open" switches and have had easy resets since then. The switch method also keeps one informed of the state of the battery :)

 

A switch does the exact same thing, only that now, I don't have to worry about pressing any switches, just get up on the bike and ride it :)

 

 

Dan

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Morning Dan

 

I think we are talking about or looking at two different failure modes here.

 

The first is ABS failure to initialize and self test at key-on and the second is ABS default and stop-working once initialized and moving down the road.

 

The first key-on is a double hit as the ABS controller monitors the system green input wire (ABS power-in for voltage). The failure here seems be in the 9-10 volt range. Keep in mind on this one that at (first key on self test) the starter motor can draw the system power low enough to set the failure code lights. (this is the most common failure mode)

 

 

At first ride away the ABS controller also cycles the large internal ABS shaft motor to verify piston movement and calibration. This large high amp motor cycling can at times lower the system voltage enough to set the ABS fault lights if the engine is running slow enough or at near stall. (not a common failure but can happen)

 

Here is the worrisome one-- When riding down the road the ABS motor is silent so no current draw on that. The ABS could be happily plugging along at 10 volts with an alternator failure but the ABS lights will stay off as it still sees enough voltage to keep it’s processor alive. The problem occurs here (instantly) at an emergency stop as not only does the brake light come on and draw some current the ABS motor starts to (or tries to) run , that significantly lowers the system voltage rather quickly then the ABS faults and quits working. (this is the dangerous one if you depend on the ABS to ALWAYS save your butt).

 

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My experience with this was that I ALWAYS got a cold ABS fault first thing in the morning, yet also got a healthy crank for startup. I tried waiting 10 or 15 (or more) seconds before hitting the starter, but that had no effect. So the ABS was initializing while the fuel pump was priming, but that would have been about it. I'm not sure how low the voltage can be to cause the ABS to fault, but still allow a healthy starting motor crank.

 

Another observation is that these bikes seem to ABS fault more frequently/easily as they age. Some have reported that when the bike was new, the ABS fault was always at battery end-of-life. But as the bike aged, ABS fault was more likely to happen when the battery was as new as 6 months to a year old. Antoine in his article (link above) indicates some variation in typical charged voltages of differing battery types as a possible explanation.

 

I have had a couple of induced ABS faults, when I had an intermittent break in the ignition wire set. That would cause a momentary key-off event that caused the voltage to drop (and in eventually, the bike to stall). In this case, it was a legitimate fault.

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Hi all,

 

I have done the abs relay mod yesterday so that it will not throw errors if the battery is weak. All is good now, or at least as I can test it since my bike is indoors.

 

Just for my knowledge, what's the voltage across the battery leads that the ABS starts to not work? 10V? 9V?

 

Dan.

 

My understanding (from memory) is that the ABS fault voltage was around 10.2V when Motronic version 2.2 was current. With Motronic 2.4 the undervoltage limit became 9.7V

 

regards,

 

Ian

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Hi all,

 

I have done the abs relay mod yesterday so that it will not throw errors if the battery is weak. All is good now, or at least as I can test it since my bike is indoors.

 

Just for my knowledge, what's the voltage across the battery leads that the ABS starts to not work? 10V? 9V?

 

Dan.

 

My understanding (from memory) is that the ABS fault voltage was around 10.2V when Motronic version 2.2 was current. With Motronic 2.4 the undervoltage limit became 9.7V

 

regards,

 

Ian

 

Thanks!

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