Battery or Alternator?

[tor1150r]

The battery on my 04 does not keep a charge. Even after a day out riding 400 kms, the next day it doesn't turn the engine over. I have jumped it off my car (with car off) to get going and it's fine for the remainder of the day, regardless of how many times I stop and start.

When I charge the battery over night, it stays ok for a while as long as I ride it every day. If I miss a day.........it's jumper time.

I am getting a replacement battery from BMW (confirmed warranty). I'll have them replace it when I take it for winter storage in 2 weeks.

My question is:

Is there any way I can tell if it's the battery or the alternator?

All else works fine. Clock, lights, access plug and grips.

[tor1150r]

Thanks Frank. This I can try tonight.

[tor1150r]

It sounds as if it may be the battery. Your dealer testing out the charging system would/could tell you if it is putting out the required amount. There is a “backyard” method, which works quite well. Wait until dark and shine your headlight on a flat surface. Let your engine idle, and then rev it up in short bursts. If your headlight gets brighter as the R.P.M.’s go up and dimmer as they go down, your battery is normally bad. If the headlight beam stays the same, your generating system is bad.

I hope this helps,
Frank

OK..now I'm thinking about this......
The headlight will do 1 of 2 things (described above). Is there a 3rd scenario that would indicate of the battery/charging system is functioning properly?

The only other case I can think of is if the headlight gets brighter on a rev, and does not dim after releasing the throttle.

[R4R&R]

My '04 had a battery problam last winter and they swapped it out under warranty. The warranty guy mentioned that they had a bad batch of gel batteries go out in new bikes, and mine could've been one.

[SLEDGE]

Get it cheecked out. A bad battery can over work the alternator and cause it to fail, if the alternator is charging at max to try and keep the battery up it can cause other problem, burned out bulbs, perhaps make the engine electronics act up ect. Cheek the belt out too. I wouldn't be surprised if it were the battery. good luck.

[CycleRob]

tor1150r,
It's the battery. The Gel cell batteries are easily ruined by overcharging, the plug in the wall type . . . and their longevity hasn't been good from what I've seen in the new bikes. If it was the alternator, it wouldn't run longer than a few minutes after a jump start. The electrical load plus the headlight would guarantee that.

Edit:
When you jump start your bike, "make" and "break" the jumper connections with one swift, no bounce, no drag, one spark movement. The car should be off. Bike key off, connect the dead battery negative last. After the bike starts, leave the jumpers hooked up, bike on fast idle, over 2,400 rpm for 2 minutes, so the bike charges the donor battery - - minimizing the traumatizing "break" connection spark. The less you jumpstart a dead battery computer equipped vehicle, the better.

I wouldn't worry about the alternator. It has so much automotive quality power that it can handle any battery shortcomings without harm. The weakest link in the charging system is the (slipping?) belt.

[Acacia]

Do you have, or have access to a digital multimeter?

Read the voltage of the battery at rest. If it is not in the 12 v plus range, or down as far ar 11.5 particualrly after a nights rest, you have a battery problem. Some batteries on their way out might register 12V plus but cant turn the starter.

With the motor running - you should be getting a reading of 13v plus if the alternator is working. It takes about as long as you have taken to read this to do this series of tests.

[tor1150r]

Thanks all.
Glad it looks like the battery more than anything else.
Bike goes in sooner than I thought for the winter.

[Simon D]

Say Frank, that's just not true y'know. We Brits drink warm beer 'cause that's how we like it!





We have warm MILK 'cause Lucas make our refrigerators!

[BlueBeak]

Just for the sake of completeness, what's the nominal draw off
the battery with the key off for an unmodified RR?

The dead-in-the-morning-battery blues are common amongst
the improperly-installed-aftermarket-radio-amp crowd.

Just wondering if there's an improper draw that might start the
same cycle with a new battery.

[tor1150r]

I picked up a digital multimeter.
I'm not a mechanic (but will do a little reading over the winter!)

I know my battery will need a boost when I go to start it tomorrow (winter storage day...going to the dealer, 10 kms away).

If I use the meter tonight on use the exterior battery terminals, I assume this will tell me the present voltage of the battery. Is it safe to assume this level will increase when the bike is running?

[BlueBeak]

I picked up a digital multimeter.
I'm not a mechanic (but will do a little reading over the winter!)

I know my battery will need a boost when I go to start it tomorrow (winter storage day...going to the dealer, 10 kms away).

If I use the meter tonight on use the exterior battery terminals, I assume this will tell me the present voltage of the battery. Is it safe to assume this level will increase when the bike is running?

Voltage only tells you the current state of the battery.
On lead-acids, sometimes it is obvious when a cell is bad, because
the voltage is down even after a full charge. But I'm new to gel cells
(probably like most here), so I'm not sure what voltage will tell you,
other than that it's low, or it isn't.

If your new meter has an Amperage setting, this is the thing you
really want to see. You do have to be careful, as most "toy" DVMs
only handle a few milliamps. If all is right with your bike, and it
really just is the battery, then this will be plenty, but if you have a
serious draw (the kind necessary to draw down a freshly charged
battery overnight, every night), you could end up popping the fuse
in the DVM.

So, you do have to disconnect the negative terminal from the
battery and put the Ammeter in-line to test the draw.

Then, someone needs to tell us what the nominal draw of an
unmodified RR is for comparison.

That would at least rule out the possibility that the same thing
will happen with the new battery.