'99 1150GS starting/not starting + battery charging/not charging

RSavage

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I've read the past threads on battery/starting problems but still feel the need to air the symptoms of my particular electrical problem - if only 'cos it might make me feel better.

Last May we rode from Calais to Limogues non-stop apart from fuel/Red Bull/Marathons. Following morning the bike was dead - no clicks from solenoids; nothing. Bump started the b*******d and all was fine for the rest of the week. Into the garage and on with the CTEK to look after my Odyssey battery. Did the National Rally in July - lots of stops and starts plus riding through the night with heated grips, 2 x 50W HIDs and 2 x 55W halogen floods - without a problem. Back in the garage - without re-connecting the CTEK. It started fine in October, rode about 13 miles then left it for an hour. When I came to start it there was a fair bit of turning over but no actual engine starting. Jump started it from a car. Back in the garage on the CTEK.


I've fitted a CTEK Battery status thing http://www.motorworks.co.uk/bmw/products/large_image.php?p=ACA56382&desc= because I've never been convinced that all is well with the charging circuit.

Jump to yesterday.

Take the bike out for the MOT test. Starts fine and off we go. Dip beam on. Battery thingy happily flashing green except for a couple of time when it flashes yellow. So, when I'm out of the fog off go the lights. Battery thing back to green - except for one period (at traffic lights) of flashing red. (Much angst). Complete MOT test and return home (dip beam on) (30 mile round trip). Flickery thing mostly green with a bit of yellow.

This morning: Won't start. Certain amount of churning but no starting until battery becomes too discharged to turn the starter motor.

Back on the CTEK all day and, according to the CTEK the battery is fully charged.

Whip the seats off and connect my Fluke 77 to the battery connections:

12.99 volts with ignition off.

13.6 volts at idle, 2K and 2K5 rpm with no added load

13.4 volts at idle, 2K and 2K5 rpm with dip beam on

12.2 volts at idle, 12.7 at 2k and 2.5rpm with everything on - (as described above plus 2 x 21w rear fog lights)

I should say that these voltages were measured straight after starting and that the no-load idle voltage had risen to 13.8V by the time I was about to pack up.

Any suggestions would be welcome.


BTW the starter motor was replaced in May 2008 with a Valeo one from Sherlocks after the previous one seized. My local auto electrician has had it apart to check for detached magnets etc.

TIA

Richard

(and sorry for the long post. I'm off to the Pyrenees in May and wondering whether I should bite the bullet and buy a 2010 R1200GSA)
 
Assuming the battery is ok, the engine running voltages shouldn't be dropping so much IMO as that shows you're not charging if you're below about 13v.

IIRC on my 1100GS the voltage hardly changes at idle with nothing on to grips and headlight on full. From memory the extra lights your bike has is only drawing another 8 amps so on a serviceable system, they shouldn't flatten the battery.
 
Doesn't sound like it's charging properly to me; you need about 14.5 volts at 2k rpm with no load across the battery to charge it.
Bear in mind that a 12v battery is 'actually' 6 cells of 2.2 volts, i.e. 13.2v nominal, so 13.4-13.6v is not a good charge.
I suspect that you have half-wave rectification only from a partially buggered diode pack in the alternator; this gives a tiny charge, but not enough to sustain it long term.
 
I was wondering about a faulty regulator <sigh>

Do you suppose that I could check for a faulty rectifier with a 'scope, rather than having to pull everything apart to get the alternator out for testing? I've been reading the service manual and I don't like the bits about removing the Motronic unit and ABS modulator.

Richard
 


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