Alternator technical info and possible 840W upgrade!

  • Thread starter Thread starter Manni
  • Start date Start date
Manni said:
....... if I don't use the bike for more than 3 days (unless I know the battery is full, ie optimate or motorway + 4000rpm for more than 1hour), the battery gets depleted ......
Click to expand...

Manni,
had a similar problem with my R75/6 battery. Took to disconnecting the battery when the bike wasn't in use and the battery would hold its charge, Found the problem in the diode board where one of the diode has failed. The battey was discharging back thru' the board and took out the starter solenoid.
I suggest that you check your rectifier.'
 
Now this is juicy (bad pun intended)!

Thanks nud1e, but I've collected some data which may help us understand the problem better and make a more precise diagnosis!

Okay, so this morning, I went to Maplin, fetched the most precise digital multimeter that I could get for a tenner, calibrated it on 20V, and as soon as I got out of Maplin I did some readings on the battery. Remember, I fully charged the battery yesterday afternoon (with Optimate, it took 3 hours), then I had a 1 hour trip to and from town (mostly at 4000rpm) in the evening and then it sat still for the night.

This morning, the trip to Maplin took 20mn, which I did again mostly above 4000rpm (this means 1st and 2nd only, not that I was trying to kill as many pedestrians as possible!). As we'll see, it was irrelevant, but I didn't know this at the time...

So out of Maplin, the battery (engine off) read 12.75V (steady).
I switch the beast on, it reads around 13.80V at idle (within a .20V range).
Note: I start with the choke, and the battery indicator disappears immediately, idle rpm around 1100rpm).
Now comes the juicy bit: I go to 4000rpm, still 13.80.
4500, 5000 rpm (glad my engine was warm), still the same: 13.85, anything between 13.78 and 13.90, but not above).
Now if I understand well, that means that
MY ALTERNATOR DOESN'T KICK IN TO DELIVER THE FULL OUTPUT ABOVE 4000rpm!!!!!
So it may explain better why my battery goes flat: when I THINK I'm fully charging it on the road, making sure I'm above 4000rpm, I'm actually depleting it with all my goodies (GPS, heated grips, ipod) which I try not to use in town. Then when the bike sits for a couple of days, the battery is not full as I think it is, it's almost empty. And that's why it loses its charge so quickly. Does that make sense, or do you think the battery is dead anyway on top of the alternator having a problem?
At least it means that the permanent load (alarm+autocom+nokia) doesn't drain the battery when I'm riding.

Last bit of data:
When I got home after the Maplin trip back, I read the battery again, engine off: it said 13V (so it had charged from 12.75 to 13V in 20mn town riding below 4000RPM).
I'm going to read it tomorrow after 24H and see what it says...

In the meantime, what do you think?
 
turn your lights on and take a reading - put the battery and alternator under some load, then se what the reading gives you .
The readings seem ok to me, the alternator seems as if it's working - how many volts do you want to charge your battery -

it sounds like ( as much as can be gleamed from your posts) that your battery isn't holding a charge .

:banghead: :banghead: :banghead: :banghead:
 
Thanks Steptoe, but my bike is a 2004 so the lights are always on.
What do you make of the fact that the voltage doesn't go up with RPMs (same value at 1100 and 5500rpm)?
 
Manni said:
Thanks Steptoe, but my bike is a 2004 so the lights are always on.
What do you make of the fact that the voltage doesn't go up with RPMs (same value at 1100 and 5500rpm)?
Click to expand...

it's the regulator limiting it.

airhead bmw's are regulated to about the same unless you fit the "high output" regulator.

it would seem oilheads are similarly capped.

like i said earlier, i don't have the official specs (can't find them in the manual) but it looks like your charging system is ok.

edit: you could try leaving the bike with the battery disconnected for a while, see what it's like when you start it up again.
if it's ok then that exonerates the battery going flat & points towards a drain.

my money's on the alarm. f*cking useless things IMO.
 
cookie said:
have you done a voltage rise test on the charging system?

check battery voltage

start engine, note voltage reading accross battery

rev engine to 4000, note voltage reading accross battery

i don't seem to have the factory specs here, but battery should be 13.5v standing, rising to about 14/14.5v when revved.

if it goes below 13.5v it's discharging.

ps. cheapo multi meter from machine mart @ about 12 quid will be perfectly good enough for this application (and most others too).
Click to expand...

Well I got confused by your earlier post then, I thought this was a way to check whether the alternator was delivering full output or not... If the voltage is capped, is there another way to check that? How do you read the amperage?

I guess if all the readings look good to you all and mean that my alternator is fine, then I'll have to see how fast the battery drains in 24h, maybe disconnect things one after the other to see if one of them could be the culprit.
I know that alarms DO drain batteries, but I've always had one week safe margin with my R1150RT and with this GS before it started to go wrong.
The Nokia BT thing is supposed to switch itself off, but maybe it doesn't (it's got one lead going to positive on the battery, one lead to negative, and one lead going to the same switched power going to the autocom, that's the one that's supposed to switch the thing on or off (plus I think there is a 2mn auto timer off).
If I don't find a draining culprit, well, I'll replace the battery then!
Thanks to everyone for your help.
 
Manni

Can you confirm that you have checked:

  • the tightness of the poly-V belt?

Now you've got a multimeter, set it on the lowest value resistance scale it offers and measure the resistance between the battery -ve terminal and the frame of the bike. You should get a reading of 0 ohms. If you get anything higher, you have a poor earth lead connection.

With the bike all switched off, disconnect a battery lead, set your meter to the highest current reading it has, and connect in line between the battery and the lead that you have disconnected. If you get a very low reading, increase the meter scale until to can measure how much current your bike is using when everything is switched off. Identify what is using the juice.

Next test: set the meter on 20v scale and measure the battery voltage. Pull out the spark-plug leads and crank the engine for, say, 10 seconds. Measure the voltage as you crank. What does it drop to?

Greg
 
Manni said:
I'm really tired of getting a flat battery when I don't use the bike for more than 3 days
Click to expand...

This seriously suggests that you have a battery or a current leakage problem.

How does your flat battery manifest itself?

Greg
 
Simple diagnosis with a meter:

Assuming you have a Datatool System 3 Alarm, put your alarm into maintenance mode and disconnect the battery. To do this, switch on the bike ignition as normal with the system disarmed, then press and hold the round button on the transmitter until the alarm beeps, then switch off the ignition. The alarm will give a confirmation beep every 15 secs. It should only emit one beep at a time. If more than 1 beep:

2 beeps - Power failure (Alarm) - Fuses failed, wires cut
3 beeps - Hot wire detection - Ignition tampered with
4 beeps - Movement detection - Bike has been moved
5 beeps - Nudge detection - Bike has been nudged too many times
6 beeps - Tamper circuit - Protective trigger (seat) switch has been initiated

If this is the case, re-arm the alarm then repeat the steps to enter maintenance mode to give 1 beep only.

Connect the multimeter as an ammeter in SERIES with the battery positive lead, making sure your red meter leads is on the correct Amps connection and the black on the common. Reconnect the battery negative lead.

Note the current draw with the alarm in maintenance mode (ie off). There should be virtually nil draw from the battery as the bike and alarm are shut down.

Put the alarm back into normal mode and note the current draw on the ammeter. If there is a significant difference when armed then the alarm current draw is the problem. If no change, but the current draw is high anyway, something else on the bike is faulty, perhaps a blown diode in the voltage regulator causing the excitation circuit in the alternator to be energised when the bike is stopped.
 
Gregmasters: thanks for these sugestions. No, I haven't checked the alternator belt, but everyone seems to assume that the charging system is fine.
To answer your question, my flat battery manifests itself by a complete loss of power after 3 days without driving (I mean complete, clock reset, not enough power to start the bike). If I drive everyday, it's kind of fine. The second day, I can "sense" that it's difficult to start the engine, but the battery still has enough power to do so. The third, it's dead flat.
I've just done another reading of the battery, in less than two hours it went from 13V to 12.70...
I've tested the earth, I read 0ohms between the neg and the frame.
I don't have time to do the other tests right now (I've got too many leads - one SAE for the tankbag, one for the heated jacket, one for the optimate - connected to the battery and it's going to take some time to undo all these without doing a short!), but I will as soon as possible. I assume it's safer to disconnect the negative leads for the tests, am I right?
Pukmaster: I'll try your tests as well as my alarm is a datatool 3, thanks a lot for the suggestion.

Update: 10mn later, it's down to 12.62V. I've disconnected the Nokia BT (last thing I've added) to check if the drain stops. I also forgot to say that the lowest resistance setting on my multimeter is 2000ohms. I hope it's low enough to test the neg-frame thing... I'll do the other tests when it stops raining (bike is parked on the street, hence the problem with using the optimate!).
 
Update (quick test between rain showers): at around 5pm, the battery charge level was still 12.60V, so I thought I had found the culprit, only to realize that the Nokia BT thingy was not disconnected (I took out the wrong connector...).
I switched the engine on, and on idling, in 5mn, the battery was back at 13V (level read while idling: just under 14V). Then, again, as soon as the engine is stopped, it started to deplete very quickly.
So I've done PukMeister's alarm test, and when I put it in service mode it gave me three beeps (hotwire detection). I rearmed it and put it back to service mode. Only one beep now. By that time, the battery charge level was 12.60V.

So I've left the alarm in service mode (the bike is attached to a post!) and I've disconnected everything (autocom, nokia thing). In theory, there is no drain on the battery (unless something is faulty).

If the level still goes down, then I'll go through the more in-depth tests (weather permitting)... But it looks more and more like the battery is dead...
 
You say that it's a gel battery.

Why, on a bike that only 16 months old, did you change from the original equipment battery?

Greg
 
I didn't! My GS came with a stock Gel battery (sealed, no maintenance), at least that's what I was told... Wasn't it standard on the last R1150GS to be produced (the dual spark ones?).
This is also why I didn't think initially that the battery was faulty... 16 months is not much, so I'll ask for it to be replaced under guarantee.
 
Just for "closure", I got the battery replaced under guarantee by the same (BMW 19A Gel battery) on thursday. BMW Battersea did it and I asked them to adjust the iddle as well as it was a bit low and certainly was not helping in town. They did that and a throttle body sync. Didn't charge me anything.

The battery is fine now, it drops to 12.96V after a short while and doesn't deplate significantly after 24h. Starts no problems, so it looks like it's sorted!

So thanks all for your patience and for giving me an opportunity to learn a lot. It also helped when I got to BMW to convince them the battery was faulty and get it replaced under guarantee without too much haggling.

Cheers! :clap
 
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