Alternator paranoia - Volt Meter?

[Clive]

My 1200 is currently having it's 3rd alternator fitted - it was only showing 12.1 volts across the battery compared to 14.5 volts when it was first replaced back in December. I don't know if alternators gradually or suddenly die but paranoia has crept in and I was wondering if anyone knows of a suitable volt meter that I could somehow wire in for a permanent display.
Any suggestions ?

 

[John Armstrong]

I'd be surprised if the alternating was dying, more likely the rectifier, or what the 12GS uses as one. An easy way is to get a dvm and attach the wires from it into a plug that'll go into the accessory socket. It won't give a "true" alternator output, but at least you'll be able to monitor the differences between engine running / not running.

Could also do the same across the battery to see what's happening without the can-bus etc messing about even more.

 

[pomm001]

My 1200 is currently having it's 3rd alternator fitted - it was only showing 12.1 volts across the battery compared to 14.5 volts when it was first replaced back in December. I don't know if alternators gradually or suddenly die but paranoia has crept in and I was wondering if anyone knows of a suitable volt meter that I could somehow wire in for a permanent display.
Any suggestions ?

Alternators in general dont give problems, you have had some bad luck.
I did see a small LED stip panel with about 6 small LEDS in it , 2 red, 2 amber and 2 green.
They are triggered by different voltages, so you should be showing green when charging ( ie battery voltage is up ) only a few quid and attaches with sticky back tape, but dont for the life of me remember where i saw it , i thought it might have been on nippy's , anyone else seen them ?

.

 

[Tarka]

I did see a small LED stip panel with about 6 small LEDS in it , 2 red, 2 amber and 2 green.
They are triggered by different voltages, so you should be showing green when charging ( ie battery voltage is up ) only a few quid and attaches with sticky back tape, but dont for the life of me remember where i saw it , i thought it might have been on nippy's , anyone else seen them ?

.

MATKAT`s got one on his Airhead......I wired it in for him....it`s quite cool

 

[Jimb]

Farnell's

Farnell's Electroncs in Leeds do an LED one that's just right, check out their website http://uk.farnell.com/jsp/home/homepage.jsp

 

[Mouse]

OK stupid question time - if not low alternator output, what triggers the "battery" warning on the bike's display?

 

[John Armstrong]

OK stupid question time - if not low alternator output, what triggers the "battery" warning on the bike's display?

Low battery voltage? Finding out what's causing it though is the harder job.

For example, when you start the bike, the light is on because the alternator isn't supplying enough amps to charge the battery, but the alternators not faulty is it?

After start up, assuming the alternator and the rectification is good the light will go out as long as the battery is ok. If the battery is fcuked then the light'll stay on IMHO.

If either the alternator or rectifier is fcuked then on goes the light, probably, because they may give just enough amps to keep the light off, but not enough to charge the battery up if you keep on starting the bike up.

 

[Clive]

OK stupid question time - if not low alternator output, what triggers the "battery" warning on the bike's display?

Well, having had two alternators "go" now, each time I got about 3 minutes "warning" - you get the red triangle battery warning light come on (which you may notice if you are paying attention), then a mile or so later the servos stop working (residual braking), then another mile or so later the engine starts to misfire (presumably the fuel pump giving up) then another few hundred yards you are pushing it
There is not enough juice left in the battery to crank the engine but lights/indicators etc still work.
So I suspect the warning light comes on when battery voltage drops below a certain point - but that doesn't appear to be much before servos/fuel pump die - enough time to get to the hard-shoulder from lane 3 I suspect

 

[Clive]

OK stupid question time - if not low alternator output, what triggers the "battery" warning on the bike's display?

Also after trickle charging the battery for several hours the bike did start ok - checked with a multi-meter and there was only 12.1 volts across the battery - however the battery warning light wasn't on then

 

[John Armstrong]

Also after trickle charging the battery for several hours the bike did start ok - checked with a multi-meter and there was only 12.1 volts across the battery - however the battery warning light wasn't on then

So if the warning system is designed to light up at 12.0 volts you'll get no light. Which is why you need an ammeter and voltmeter to accurately diagnose charging problems. And to know what the outputs shold be and what the tolerances are.

 

[Mouse]

So it seems the warning light is rather useless, because the voltage for it is set too low ... if it was set to come on when the battery votlage dropped below say 13V, that would seem to be more useful.

 

[John Armstrong]

So what you want is a lack of charge light / meter? AKA as an ammeter

 

[Clive]

So what you want is a lack of charge light / meter? AKA as an ammeter

Ok - being a bit of an electricky numpty, can you explain further?

Measuring Voltage across the battery terminals appears to give approx 14.5 volts when alternator is "good" and approx 12.1 volts when "bad".
Where would the ammeter be connected and what would it be measuring - amps output by the alternator ? Would that be a constant value or depend on battery charge state?

I've just got back home with a new alternator fitted so am interested in taking some readings with my multimeter - for future reference

 

[shugie]

Ok - being a bit of an electricky numpty, can you explain further?

Measuring Voltage across the battery terminals appears to give approx 14.5 volts when alternator is "good" and approx 12.1 volts when "bad".
Where would the ammeter be connected and what would it be measuring - amps output by the alternator ? Would that be a constant value or depend on battery charge state?

I've just got back home with a new alternator fitted so am interested in taking some readings with my multimeter - for future reference

I'd be looking to put the ammeter into the battery lead, to see if more current flows into that out, over the long term. After all keeping the battery charged is what keeps the voltage up enough for the bike to keep going. Bear in mind the ammeter needs to be able to cope with the start current.

I would be having a look at the battery as well, if its the original one it might be a bit shagged by now from being run flat.

Anyone know if the 1200GS charging circuit is the same as the 1150GS, or does the canbus do something clever like remote battery terminal voltage sensing to control the alternator?