What's wrong here, battery or alternator?

[muppix]

Long story short: I'm off to the Alps soon, think my alternator may be buggered, would appreciate some advice.

What's happened was ...

I just don't get out as much on the GS as I'd like. Apart from a dreadful ride into work last week, 30 miles each way in rush hour traffic, it's spent most of it's time locked in the shed, occasionally sharing an Optimate with the DR-Z and no doubt dreaming of happier times. Prior to the work run she'd not been used or charged for a couple of months, and I was quite surprised when the engine turned over eagerly.

That was last week. This morning I got her out for a quick blat up the road to take the piss out of ... err ... "visit" a friend with seven stitches in his foot after stepping on a craft knife in his lounge. Engine turned over and started first time, just like always. Five miles up the road I stop for fuel, and again she starts on the button, keen as mustard. Another five miles to the caff, I swing by for some croissants on the basis that I've not had breakfast yet and he's not one for flowers.

Come out, put key in ignition, and straight away something doesn't look right - the 'check' flickers on the LCD, which then goes dead. And comes back on, goes dead, comes on, stabilises. I press the button but only get a click from the solenoid, which sets the screen off again. Cue 5 minutes of animated sweltering and swearing, much to the amusement of those sat at tables right where I've parked. While I'm waiting for the nice man from Carole Nash recovery to arrive I try the key several times more (well, you have to, right?) only to get the same predictable result: no fuel pump priming, no engine starting. Sometimes the solenoid clicks, sometimes it doesn't. Sometimes I can use the horn and flash the high beam, both of which look / sound fine, sometimes I can't. At one point I see 'EWS' on the display and start to fear the wurst, but I've had that ring antenna recall so maybe it's the electronics that are fecked?

When the AA patrol man arrives in his van he reckons it's the battery, apparently this weather kills them. News to me, I thought it was the cold, but I'm not about to argue. He gets out his starter battery and the jump-leads, hooks her up, and she turns over first time. Phew - so it's not the electronics. We disconnect the jump-leads, and within a couple of seconds the engine dies again. This surprises both of us, but I think he's not trying to show it, so we repeat the procedure with the same results.

Time for the multi tester. Before starting the battery reads 12.5V (connected to bike), dropping to a measly 6V once the ignition is on. Once we start her (with the external battery, which is then disconnected) she reads between 12V and 14V depending on revs, but drops to 0V every couple of seconds in a reliable rhythm before dying altogether. This worries me, because I always thought that the alternator makes enough juice to keep a bike running, even if the battery is shot and won't hold a charge. Mr. AA thinks otherwise, and gives me a lift to the bike shop so I can buy a new battery which he then fits for me. Naturally it starts first time, and shows between 14V and 16V with the engine running. No more intermittent dropping to 0V, business as usual. I ride 10 miles home and put her on the Optimate, he takes the old battery away for recycling.

So, battery or alternator?

I really, really want it to be a duff battery. In the 6 years I've owned the bike from new she's refused to start only once, when I left it too long between rides and the weather was unusually cold. Now that it's happened again I've started post-rationalising and it's not looking good, given my limited knowledge / experience:

Case for a duff battery (pretty weak, IMHO)

• Bike works again when it was replaced
• It's had one battery from new, nearly 6 years old

Case for a duff alternator

• Bike started fine this morning, despite having stood for a while
• Started again after just five miles - easily possible with a healthy battery that's not being charged - but refused to start a third time shortly afterward
• Bike started when an auxiliary battery was called into play, but died as soon as that was removed. Again, I thought that once started it should run and run, regardless of whether a battery is even connected

So, is there anything I can do (apart from ride her until she dies) that will settle the battery / alternator argument? My next chance for anything longer than a half-day outing is a ride to the French Alps at the start of September, and I'm not loving the prospect of something screwing that trip.

Any advice gratefully received!

Mup

 

[Beemerman59]

If you're getting +14v across the battery with the engine running the alternator's good.

My opinion=battery.

 

[Paul Everton]

I bought one of these to keep an eye on my battery and charging system.... Works a treat May come in handy for you for peace of mind on long trips...

http://youtu.be/Tg4cW7T6Hw4

 

[ianboydsnr]

I have one of these to fit my guzzi, not tried it yet though!

http://www.ebay.co.uk/itm/150474037874?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[Pukmeister]

What Beemer man said, 12.5v nominal across a healthy battery with engine off, rising to 14.7v with alternator charging at revs.

If you don't see about 14v you may have a faulty alternator or voltage regulator/rectifier within the alternator itself.

 

[Blobby]

Sounds like a duff battery cell to me so I think new battery will have solved the problem.

 

[Steptoe]

.This worries me, because I always thought that the alternator makes enough juice to keep a bike running, even if the battery is shot and won't hold a charge.

It does on almost every other vehicle..... but not on the BMW 1200GS canbus system.
If the battery is fecked the bikes system shuts things down.

Great if you're in the middle of nowhere with a goosed battery. On an 1150 (for instance) you'd just bump or jump start it and get to somewhere you can replace the battery or get help.

But not on the rugged built to "go anywhere in the world" 1200GS you can't.


More than 20 years ago i had a battery go tits up on my harley when i was a long way from home. Got it bumpstarted and thought it'll get me home....... wrong.
Well it did get me home. Just.
But i found out something by accident as the engine died and i put the indicator on to get off the road out of the traffic flow.... the engine would only run with the L/H indicator flashing. But the interesting part was the engine only ran when the light flashed on..... so i got home with the engine surging forward as the indicator flashed on, then died as it it turned off, then surged forward as it turned on, etc etc etc all the way home. One of the more interesting rides a had through london..

The other was on one of the first norton rotary bikes, the one that idled on one rotor and used a micro switch as you open the throttle to start the second rotor, in effect from one cylinder to two at the flick of a switch.. anyway the clutch cable broke when i was on the other side of london.

Imagine, if you will, riding a bike with no clutch in heavy traffic with traffic lights ahead and a bike going from half power to full power and back again in a fraction of wrist movement as you rode along a crowded road at walking pace trying to judge when the lights ahead were going to turn green.

 

[B4ndit]

Whilst we are swinging the lantern. I had a vehicle that acted like a clown car. No power and lots of back firing., After stripping it down and checking everything it was the reg rec connection that had corroded due to water ingress. Now all my vehicles have voltage displays. It helps a lot with possible problems and costs literally pennies to do.

 

[Steptoe]

Now all my vehicles have voltage displays. It helps a lot with possible problems and costs literally pennies to do.

An amp meter will show up the problems better than a voltage meter/display.

 

[tanneman]

The voltage only serves to indicate the potential of the battery to deliver the juice so to speak. Measuring the amperage will tell you if the battery is duff or good to go but for that you'll need a battery tester with a build in load. As batteries are rated by their ability to do work eg amp/hour the test needs to be conducted over a time period to monitor the degrading in the current flow. Simples really. Volt meter to check on the alternator and amp meter to check on the battery.

Just to confirm what Steptoe said. You'll be ok with a normal wiring set up as per pre CANBus. The electronics require a certain amount of current to keep it going, in fact the software that does the calculations require a current to set and maintain the logic gates. There will be a threshold of current draw that is needed. Once below that threshold the operation of doing the calculations can't be done reliably and in order to protect the system it has a build in on/off switch. Happy days, but I still like my bike. Just keep the battery hooked up ever so often not all the time and check on the terminals as they tend to vibrate loose over time.

 

[muppix]

Thanks for the replies everyone, that's a tremendous load off my mind. Good old canbus, eh? I do still wonder why it ran happily for the first few miles including two starts, but I guess that the battery was shagged in such a way that it would not accept a charge, and only deliver one. Live and learn!

Thanks again,
M.

 

[DrFarkoff]

Don't feck about the ECU does not like high voltage spikes

It could get a LOT more expensive than a battery if you don't get it changed ASAP

 

[Pukmeister]

If you use the analogy of water, volts are like pressure and amps are like volume.

You can have an almost empty battery that still shows volts, like an almost empty pressure vessel that still shows a pressure reading.

 

[Bendy toy]

To expand the water pipe analogy:

The static pressure can look ok with no flow but as soon as you open the taps the pressure drops so there is now a dribble. No flow and now no pressure either. Batteries are the same. With no load they can look ok but voltage drops when they are asked to do anything useful.

A wired in volt meter will help by showing that pressure change. If the pattern changes from normal you'll know something is amiss.

The old British bikes had a differential ammeter. It showed negative when engine off and just positive when engine running. It would swing more positive if the battery was taking charge or more negative when battery discharging. They had weak dynamo generators, so the ammeter would swing back and forth as the engine revs changed with a bigger swing when the lights were on. This was handy for slow speed commutes so you could gauge if the battery was likely to go flat. But a rising/falling voltage would give similar information

A voltmeter is much easier to fit (one wire to the battery +ve and one to earth) and gives enough information most of the time. Ive got one of these (in silver) but not got around to fitting it.
http://www.ebay.co.uk/itm/Micro-Dig...arts_Vehicles_CarParts_SM&hash=item2a0eb1ca10

 

[Pukmeister]

Since the controllers already know the system voltage, it's a pity nobody saw fit to include it in the multi-function computer display. It would save you from fitting that voltmeter.

 

[morty]

don't see the point nowadays as battery technology has moved in leaps and bounds and should be seen as a throw away item after x amount of years regardless if they are working properly.use it ,abuse it & replace it.with the small exception of failures due to poor manufacturing or QC..You'll end up with a dash like an airbus consul before long,what next a scanner to make sure you have enough tread on your boots?

 

[Smug]

Time for the multi tester. Before starting the battery reads 12.5V (connected to bike), dropping to a measly 6V once the ignition is on. Once we start her (with the external battery, which is then disconnected) she reads between 12V and 14V depending on revs, but drops to 0V every couple of seconds in a reliable rhythm before dying altogether. This worries me, because I always thought that the alternator makes enough juice to keep a bike running, even if the battery is shot and won't hold a charge. Mr. AA thinks otherwise, and gives me a lift to the bike shop so I can buy a new battery which he then fits for me. Naturally it starts first time, and shows between 14V and 16V with the engine running. No more intermittent dropping to 0V, business as usual. I ride 10 miles home and put her on the Optimate, he takes the old battery away for recycling.


Mup

Your regulator is faulty if it is charging at 16v.

An overcharging system will ruin your new battery.

 

[muppix]

Since the controllers already know the system voltage, it's a pity nobody saw fit to include it in the multi-function computer display. It would save you from fitting that voltmeter.

+1 for that firmware hack! While we're at it, can we adjust the time it takes for the canbus sockets to power down after ignition off? Thank you.

 

[muppix]

Quick update. The new battery spent 36 hours on the Optimate, then I rode to work this morning. Voltage before leaving was about 12.8V with ignition off, 14.5V with it running at idle. 30 miles of gentle motorway later she's putting out 13.1V off, still charging steady at 14.5V with engine at idle.

I'm fairly confident I'll be all right now, but might do the commute by bike a few more times to be on the safe side.

Cheers all!

 

[muppix]

Your regulator is faulty if it is charging at 16v.

Now there's a horrible thought. Any way I can test that, apart from measuring the voltage? (or buying batteries ad infinitum)

An overcharging system will ruin your new battery.

At the risk of getting shot down in flames, it's only £50 and if it lasts as long as the OEM one it'll still be cheaper than the labour of swapping out the regulator/rectifier. Or repairing the damage if I do it myself.