Discharging battery?

[Sully]

The 2 year old BMW gel battery on my '97 RT was weakening, even tho I'd kept it above freezing each winter with periodic connection to its Battery Tender.

I took it off to get it load-tested: no good!

Ok, (grumble) I ordered a new lead-acid battery, charged it for a day and installed it. Now I've put the 'Tender on it "just to see" and it started out with the red light for an hour before starting to blink green! Hmmmm....

Disconnected the battery tender when it showed the green light unblinking, and measured 13.08 V across the battery's terminals. Ten hours later, it's down to 12.58 V.

Got the meter out, set it to 2.0 Amps- went to measure across the + & - terminals... POW! Got a big spark when the probe touched the terminal.

Ok... now check the fuses in the VOM, they're ok. Back to the bike.

Now I set the VOM to 10 Amps, and get 0.00 A.

I'm confused; can someone shed some light on whassup with this problem?

Vacation is fast approaching, wife wants to leave Sunday and I don't want to carry the 'Tender and find a willing 'plug donor' while camping.

Any help will be greatly appreciated (I've already searched this forum for "battery drain" and didn't find much help there in the 45 results!)

[jdiaz]

Are you turning the key to the running light position?

Is there any hum from the ABS pump area in front of the battery?

[Sully]

Nope, I've only turned the key to P a couple of times (just to check the parking light). No noise coming from the ABS either with the key off or after the fuel pump cycles upon turning the key on.

[jdiaz]

The only thing drawing energy should be the Rider Information Display to run the digital clock. Maybe remove the decorative panel holding it and unplug it from the back, to see if the draw goes away. The RID was the only component that failed on my '96 RT.

Any other accessories on this bike?

[Sully]

No accessories, Jon. I wouldn't expect the RID to draw much, but I'll unplug it and see.... thanks.

[Rod Sheridan]

Hi Sully, you had a big spark and a pow when you connected a meter set to measure current across a voltage source. The meter has a very low resistance in the current function, and is meant to go in SERIES with the battery, not in PARALLEL. You have re-invented the short circuit.

Since the fuses in the meter are OK, you have either destroyed the current range in the meter, or the test leads, or both.

To measure parasitic loads, disconnect the negative Battery lead from the frame. Connect the negative multimeter lead to the disconnected wire, making sure it doesn't touch the frame. Set the meter to DC Amperes.

Now connect the positive multimeter lead to the frame. Read the parasitic load current on the multimeter. Change ranges if you have to. Do not turn anything on, on the bike, key out of ignition lock.

regards, Rod.

[soffiler]

Disconnected the battery tender when it showed the green light unblinking, and measured 13.08 V across the battery's terminals. Ten hours later, it's down to 12.58 V.

That voltage drop is not particularly large. 13.08V immediately upon disconnecting the Tender is representative of a "surface" charge... you really should have put a small load on the battery for a few seconds before you took that first measurement. The second measurement, ten hours later, has probably been running the bike's small parasitic loads (ECU, clock) and they've removed the surface charge for you.

The bigger question here is whether it will maintain approximately 12.5-12.6V for a period of days with no help from the Tender.

...Got the meter out, set it to 2.0 Amps- went to measure across the + & - terminals... POW! Got a big spark when the probe touched the terminal.

Ok... now check the fuses in the VOM, they're ok. Back to the bike.

Now I set the VOM to 10 Amps, and get 0.00 A.

I'm confused; can someone shed some light on whassup with this problem?

What were you hoping to measure with the above procedure? An ammeter is very nearly a dead short. That big spark you saw is consistent with placing a dead short across the battery. You have blown a fuse (or worse) in the meter, certainly. The fact that it no longer acts like a dead short on the 10A setting is a big clue that you've damaged the meter somehow, hopefully just a fuse.

Again - what were you hoping the ammeter was going to tell you?

[soffiler]

The only thing drawing energy should be the Rider Information Display to run the digital clock. Maybe remove the decorative panel holding it and unplug it from the back, to see if the draw goes away. The RID was the only component that failed on my '96 RT...

The fuel injection computer will have a small drain as well.

[donbmw]

I do not know about oilheads but on airheads the diode board going bad can cause and drain on the battery.


Don

[soffiler]

I do not know about oilheads but on airheads the diode board going bad can cause and drain on the battery.


Don

Oilheads don't have a diode board like airheads, but, the same function is performed inside the alternator by.... a bank of diodes. Yes, a diode can fail shorted, but that usually tends to discharge the battery QUICKLY.

[Sully]

Trying? Hmm, yeah... I'm trying to remember how to install an ammeter, and yes, I got it wrong.

Lessee, find the spare VOM & install it between the neg post and the neg ground lead. Boy I'd hate to have damaged my Wavetek, it's only got a few hours on it.

Thanks for the leads (pun intended) here,guys.

[Sully]

Soffiler, I hoped that the ammeter would give me a measured value of the drain on my elect system while "off".

Sorry I didn't answer that in the last post!

[soffiler]

Soffiler, I hoped that the ammeter would give me a measured value of the drain on my elect system while "off".

Sorry I didn't answer that in the last post!

Ah, OK, good. Your thinking was clear, just your procedure that was a bit off. Is the meter toast, or what? Have you checked battery voltage after sitting for a few days?

[Sully]

Today is "study for my Chemistry final tonight", but tomorrow I'll try to install the ammeter and see whassup.

The meter works fine for ACVolts, DCVolts and resistance.

I've got an old Stewart-Warner ammeter in the spare parts box-maybe I mount it up on the RT, but I think it's "-30,0,+30" and wouldn't show me millivolts.

[soffiler]

Today is "study for my Chemistry final tonight", but tomorrow I'll try to install the ammeter and see whassup.

The meter works fine for ACVolts, DCVolts and resistance.

I've got an old Stewart-Warner ammeter in the spare parts box-maybe I mount it up on the RT, but I think it's "-30,0,+30" and wouldn't show me millivolts.

Er, you meant "milliamps" right??

The fact that the meter works fine on other scales means only that you did not damage the leads. Still could have blown part of the ammeter circuit, or, hopefully, one of the fuses that protect the circuit for exactly this reason. You said you checked the fuses, I know...

Do you really have the evidence to suggest the bike has an excessive parasitic drain? I guess I'm a little confused about what your problem really is.

[Sully]

Umm, yeah I meant milliamps.

The only evidence that I have that there's a drain somewhere is my observations of repeated instances where the battery tender light is red, even after an hour of 4000 rpm operation.

[soffiler]

Umm, yeah I meant milliamps.

The only evidence that I have that there's a drain somewhere is my observations of repeated instances where the battery tender light is red, even after an hour of 4000 rpm operation.

OK. Personally, if it were me, that would be enough to make me curious and go looking deeper (which is exactly what you're doing) :thumb

Of course, if this is a problem after an hour of 4000rpm operation, we've got a charging system issue, not a parasitic drain issue...

Did you mean a couple days after running an hour at 4000 rpm?

[bmwmick]

Umm, yeah I meant milliamps.

The only evidence that I have that there's a drain somewhere is my observations of repeated instances where the battery tender light is red, even after an hour of 4000 rpm operation.

Find a good amp meter and put it in SERIES with the battery negative cable. With the ignition OFF(DO NOT TURN THE IGNITION ON OR TRY TO START THE ENGINE WITH THIS AMP METER CONNECTED) you should see about 2.6 milliamps total drain. If you have more than that and you have NO accessories, you have a problem somewhere.

With the engine running at say 2,500 RPM put your VOLTMETER across the battery. You should see upwards of 13.8 Volts if the alternator is charging properly.

[soffiler]

Find a good amp meter and put it in SERIES with the battery negative cable. With the ignition OFF(DO NOT TURN THE IGNITION ON OR TRY TO START THE ENGINE WITH THIS AMP METER CONNECTED) you should see about 2.6 milliamps total drain. If you have more than that and you have NO accessories, you have a problem somewhere...

Good DATA, Mick, thanks for posting. Hope Sully is still tuned in. So 2.6 milliamps is enough to run the clock on the RID and whatever keep-alive circuits are in the ECU? Sounds a bit low based on my automotive experience where anything under about 20 is considered acceptable.

[bmwmick]

Good DATA, Mick, thanks for posting. Hope Sully is still tuned in. So 2.6 milliamps is enough to run the clock on the RID and whatever keep-alive circuits are in the ECU? Sounds a bit low based on my automotive experience where anything under about 20 is considered acceptable.

Steve,
2.6ma + - 15% is the official BMW data for key off battery drain. This is with NO factory alarm installed. I know there was a bulletin issued on this not too long ago.
A car battery has about 10X the capacity of our bike batteries too. :)

[soffiler]

Steve,
2.6ma + - 15% is the official BMW data for key off battery drain. This is with NO factory alarm installed. I know there was a bulletin issued on this not too long ago.
A car battery has about 10X the capacity of our bike batteries too. :)

Thanks again, Mick. Yes, of course, I realize a car battery has much larger capacity. I am happy to hear the official BMW spec, for future reference. I was just kind of thinking out loud that the known key-off drains (primarily the ECU) on a modern fuel-injected bike can't be much different from the one on a modern car. I wonder if they take special pains to reduce the parastic drain by design on the bike ECU?

[bmwmick]

Steve,
I sent you a PM.

[Sully]

Thanks, Mick- that's the kind of data I was hoping to find on this forum. I'll let you know what the results are.