Dear K100 forum,

I am new here so be kind. I will try and be clear about my K75 issue but I am no mechanic.

Problem:

Gel BMW battery. Battery is losing its charge. Bike starts fine when battery is full or has regular trickle charge (CTEK). I have a CTEK comfort adapter with indicator lights. The battery will stay "green" for about 24 hours and then go to red. Basically the battery indicator tells me that the battery needs recharging every 48 hours (whether or not I have ridden it). If I don't recharge it the battery will die.   

Context:

I ride approx. 12 miles per day (6 mile commute). Bike stored in garage. Naked 1991 K75 with BMW heated grips (working). Well serviced. 40k miles on odometer.  

Other issues that may be related:

The ABS works when the bike has good charge but the ABS warning lights flash. ABS stops working when the battery is low.

History of problem:

Its the second new gel battery I had put in in a few months. Same issues each time. I first was convinced that it was the battery itself and returned it to the manufacturer who replaced it. The same thing is happening on the next battery which has led me to believe that there is a parasitic drain OR I have had two bad batteries...)
 
How I have tried to fix it:

1) By replacing the battery - problem persists
2) By buying a CTEK charger which indicates that there is no fault with the current battery but it is being drained rather fast - problem persists
3) By making sure all the switches are OFF (e.g ABS, heated grips, engine kill, lights etc) when I leave it overnight - problem persists
4) Taking it to a qualified BMW garage. They were confident it was the battery and advised me to send the battery back to the manufacturer (which I did but problem persists with new battery). They said that my bike did not drain their test battery. - problem persists
5) I bought a multi-meter and tried to check the voltage with different fuses in and out. Apparently I have no idea how to use a multi-meter and I blew mine up about 10 minutes after buying it. - I am an idiot.

Hypothesis 1

The flashing ABS light is draining the battery. I know how to reset the ABS light (voodoo) but I have taken the battery out so many times I cant be bothered to reset it anymore.

If I disconnect the ABS the battery will stop draining.

Hypothesis 2

There is a exposed wire sometimes that is draining the battery. Its an old bike and one of the wires is bound to be worn somewhere.

If I learn to use a multi-meter I will detect a drain on one of the circuits.

Hypothesis 3

I have very bad luck and the 2nd battery was also a dud. The next battery I buy will also be a dud. Every battery I buy ever will be a dud.

Grateful for any suggestions/tips or locals who can show me how to use a multimeter (ideally where I can learn and not spend loads of money.)

Happy Christmas!!!

Henry

Hello Henry!

Sorry to hear you have this issue.
A fast test to verify the issue.

Testing Your Battery for Parasitic Load

Cheers
Have a nice X-mas

Hypothesis 1, no chance, that flashing ABS light should only work when the ignition is on and the engine running, so the battery is doing nothing the alternator is supplying all the electrical power.

Hypothesis 2, if that was the case then there would be a short which would blow a fuse.

The battery only serves one function, to start the bike, once it is running the battery will be charged by the big alternator that is fitted to the K. Best thing that you can do is look at a voltmeter attached across the battery, 12.2 to 12.8 volts will be enough to start it. After starting then the voltage should be above 13.5 and up to 14.1 volts, that will show that it is charging. Switch on heated grips, lights etc and make sure that the voltage stays above the 12.2 to 12.8 that you observed earlier, which means that the battery is still getting some charge. AT tickover this might be marginal, but use the fast idle lever (choke) to set it at 1500 or more rpm and it should charge. 

If the voltage does not achieve the values with the engine running then your charging system is suspect, come back and tell us.

A voltmeter is the most useful gauge on a bike, mine all have them.

Twice I have had a bad ABS drain the battery. Try unpluging the ABS computer to see if the drain stops. Both were sensitive to battery voltage and once they were fixed it stopped.

Thanks People!

I will try these and get back to you (probably after xmas).

Really appreciate putting me in the right direction.

H

I have seen a problem with the ABS relay causing battery drain on two k16v's.

The relay's stayed powered on all the time - causing the drain.

I replaced the relay's and problem disappeared.

Might be worth checking.

Ok thanks ringfad

but you need to talk to me like I am 4 years old. I don't speak this language yet.


How do I replace the ABS relay?
How do I disconnect the ABS?

hker wrote:Ok thanks ringfad

but you need to talk to me like I am 4 years old. I don't speak this language yet.


How do I replace the ABS relay?
How do I disconnect the ABS?

Don't change anything yet, check the whole system out with a voltmeter.

Hello!

You'll find the relay under the tank, with two people you can lift the tank up on the right sight, without disconnecting to much.




The ABS brain/box is in your tail rack of your bike



The ABS looks like this


It is hold by two screws, take the screws out and you will hold it in your hands. Pul it out, disconnect the connecting cable.
That's it.
The bike will brake fine without ABS.

I would first measure with a multimeter. As shown in thread 2!


Disconnecting the ABS box/brain is easy and fast, you can ride without ABS and test if Batterie is still losing power.


The relay is a bit harder to get to and you will have to know how measure it with a multimeter, or you have a known good spare one.

Cheers

Chocolate wrote:

Disconnecting the ABS box/brain is easy and fast, you can ride without ABS and test if Batterie is still losing power.

Cheers

But the battery will not lose power when you are riding unless the alternator is not working!

hker wrote:Apparently I have no idea how to use a multi-meter and I blew mine up about 10 minutes after buying it. 

Concerning the multimeter, replace its fuse, review the meter manufacturer's operating instructions—they were created to give you an idea of how to operate it—then follow the method in the link that Chocolate supplied in post #2 that affirm BobT's recommendation. It is a step-by-step procedure. Hypothesizing can come later, after dinner. 

RicK G wrote:Twice I have had a bad ABS drain the battery. Try unpluging the ABS computer to see if the drain stops. Both were sensitive to battery voltage and once they were fixed it stopped.

The ABS computer is in the tail section behind the seat. To unplug remove the multi pin plug, there is a locking clip that needs to be released then lift the plug away.
Leave it unplugged and see if that is the problem.
Your battery may already be damaged so get it load tested, most auto shops can do that.

Hi guys,

hopefully your still out there to guide me along the way. 

So... 

I charged the battery up with my ctec charger, seems to hold its charge at 13.00 after a few weeks standing on its own. 

I have hooked up the multimeter as guided by this:

https://www.batterystuff.com/kb/articles/charging-articles/testing-your-battery-for-parasitic-load.html

The multimeter across the battery reads 13.00A (see photo below so you can check how I set the multimeter up):




I pulled out all the fuses 1 by 1, pressed all the button, took kickstand down, pressed levers, wiggled handlebars etc. Remained at 13.00.

Whats next?

Thanks, 
Henry

RicK G wrote:

RicK G wrote:Twice I have had a bad ABS drain the battery. Try unpluging the ABS computer to see if the drain stops. Both were sensitive to battery voltage and once they were fixed it stopped.

The ABS computer is in the tail section behind the seat. To unplug remove the multi pin plug, there is a locking clip that needs to be released then lift the plug away.
Leave it unplugged and see if that is the problem.
Your battery may already be damaged so get it load tested, most auto shops can do that.

Can anyone send me a photo of the ABS multi pin plug?

BobT wrote:Hypothesis 1, no chance, that flashing ABS light should only work when the ignition is on and the engine running, so the battery is doing nothing the alternator is supplying all the electrical power.

Hypothesis 2, if that was the case then there would be a short which would blow a fuse.

The battery only serves one function, to start the bike, once it is running the battery will be charged by the big alternator that is fitted to the K. Best thing that you can do is look at a voltmeter attached across the battery, 12.2 to 12.8 volts will be enough to start it. After starting then the voltage should be above 13.5 and up to 14.1 volts, that will show that it is charging. Switch on heated grips, lights etc and make sure that the voltage stays above the 12.2 to 12.8 that you observed earlier, which means that the battery is still getting some charge. AT tickover this might be marginal, but use the fast idle lever (choke) to set it at 1500 or more rpm and it should charge. 

If the voltage does not achieve the values with the engine running then your charging system is suspect, come back and tell us.

A voltmeter is the most useful gauge on a bike, mine all have them.

BobT- I am worried about breaking the voltmeter!

Can you tell me the correct way to attach the voltmeter to the bike when it is running? Then I can do the above test.

Thanks!
H

The relays are not fused, only the wiring that operates them. The relays are electrically operated switches for higher loads which would burn out ordinary switches and they still have the higher load live even with ignition off and fuses removed.

You have them for horn fuel starter ABS etc and they are generally all in that box under the tank.

What may work is to pull the relays one at a time and see if you get a change in the voltage. Chocolat gave you a good diagram for the relays under the tank. Some of them as in starter relay are bolted in.

A fault inside a relay can cause this drain.

There have been cases of an alternator fault causing a drain too, but don't go there yet.

I have had a case of 2 consecutive bad batteries in the car so don't go buying anything until you have explored it all. Being methodical is the key.

When the ABS unit is in the rear ducktail it's the only item in there and held in on rubber straps that you can release. On my LT it was under the seat due to it having been a police bike in earlier times.

Your photo shows the meter is set to DC volts, not Amps. If you have it connected directly across the battery then you can start the bike and see if the voltage rises as you increase the revs. This will indicate if the charging system is performing as it should.

Mike

As mike says, connect the voltmeter across the battery with it set on DC volts. Start the bike and see if the volts have gone up. If they have then the alternator is working. The readings that you get are all in my last post. You will not break the voltmeter, if you do then buy another as they are very cheap.
If the battery is losing charge when left then the battery is past its best. If you have something attached to the battery that tells you how well charged it is, and that device is working all of the time then that is your problem.

Just reminded me of this post from Alby:-

https://www.k100-forum.com/t3621-current-tester

By plugging one of these ammeters into each fuse socket it would show if there is any current drain at each fuse.

Paul.

A little thought occurred to me. Are there any USB outlets wired on the bike?

With the meter set to DC volts and checking the battery for charging is one test. Leaving it on DC volts and across the battery and then disconnecting relays won't show a parasitic drain.

That needs to be done with the meter set to amps and connected in series between say the battery earth connection (or end of the disconnected lead) and the frame. 

Mike

92KK 84WW Olaf wrote:A little thought occurred to me. Are there any USB outlets wired on the bike?

Olaf the only thing that a disconnected USB could do is drain the battery after about 5 years!

Bob some of the USB outlets have transformers in them that stay live if not wired through the ignition and drain quite quickly.

I have a dual USB port on the K1100 and had to put a switch on it so it could be used without the ignition on. It drained the 24AH battery in 3 days.

Hker is looking for a parasitic drain on the system.  The procedure he should perform is to measure the overall current draw on the system as each circuit is enabled in sequence, allowing him to identify the failing component.  Hker needs to insert the DMM in series into the ground circuit as an ammeter to measure that draw.

1. Turn off the ignition and remove the bolt holding the battery ground cable from the transmission.
2. Insert the Red test lead into the terminal marked 10A.  Leave the Black lead in the terminal marked COM.
3. Switch the rotary switch  on the DMM to 200m setting (6 o'clock position)
4. Using short jumper wires with alligator clips, attach the red lead to the ground wire and the black lead to the bolt on the transmission from which you've disconnected the ground lead.  Now, electrically, the DMM is in series with the ground.
5. Pull all fuses in the system.  Observe the reading on the DMM; it should almost zero.
6. Carefully change the range switch to 20m and see if the reading changes.  If it shows in the hundreds, then you have your excessive parasitic current reading there.

 The expected parasitic current reading of a normally operating K100 should be about 2mA (accounts for the drain of the clock).

If you have a high drain with all fuses removed, then the problem is in the part of the system which is directly connected to the battery.  If the drain is almost 2mA with all fuses removed, then repeat the following procedure:

- insert a fuse.
- Observe any increase in the current reading
- if observed, the offending failing component is in the associated fused circuit
- remove the fuse and repeat the procedure for the next fuse position

As Ringfad pointed out earlier, the ABS relay is the most likely culprit.

Hey I'm having a similar issue with my '91 K100 RS. What do you guys think about the idea of installing a battery disconnect switch as a workaround for parasitic battery drain? I just installed a new battery but that is pretty much the limit of my mechanical abilities. To get to the bottom of the issue I would likely have to take it to a repair shop. I thought maybe a disconnect switch could be a simple and inexpensive way to address the issue but perhaps I'm missing something. Would greatly appreciate your thoughts. Thanks

manmachine78 wrote:Hey I'm having a similar issue with my '91 K100 RS. What do you guys think about the idea of installing a battery disconnect switch as a workaround for parasitic battery drain? I just installed a new battery but that is pretty much the limit of my mechanical abilities. To get to the bottom of the issue I would likely have to take it to a repair shop. I thought maybe a disconnect switch could be a simple and inexpensive way to address the issue but perhaps I'm missing something. Would greatly appreciate your thoughts. Thanks

If you suspect that the ABS brain is causing the drain on a 91 RS then you can just lift the seat to disconnect/reconnect the ABS brain. Push to the right on the metal clip where all of the wires come into the connector for the ABS brain - yellow arrow below - and rotate that side of it up to disconnect it.




Easier to install than a disconnect switch: Get an M6x45  or M6x50 knob. Put couple of nuts near the end of it and use that to connect/disconnect the battery ground near the shift lever. This is on a K75 but same thing will work on a 91 RS.

Awesome, thanks Duck. I'll give both of those a shot. Really appreciate the suggestions!

I had a similar problem on a K75RT many years ago and disconnecting the ABS stopped the drain. I sent the computer to Tosi in Japan and it has worked well since.
http://bmwk10075abs1fix.web.fc2.com/

Rick G wrote:I had a similar problem on a K75RT many years ago and disconnecting the ABS stopped the drain. I sent the computer to Tosi in Japan and it has worked well since.
http://bmwk10075abs1fix.web.fc2.com/

I've dealt with him several times before and there's no doubt that Tosi knows his ABS inside and out but if it's a relay issue then sending him the brain won't fix an ABS drain issue.

I would attempt to diagnose the root cause first.

JM02

Assuming the ABS is causing the drain:

I did some poking around on wiring diagrams and ABS I brain pinouts to figure out how to diagnose this to see if the drain is being caused by the ABS brain or a stuck relay. The following applies to all ABS I bikes: K75, K100, K1, K100RS4V as well as 93  and earlier K1100s.

Unfortunately Pin 30 of the ABS safety relay (the big dark blue Hella relay) is a solid red wire that connects directly to the battery and is unswitched so if that relay stays closed then it's sending power to the ABS modulators even when the bike is turned off.



There are two ways for that relay to stay closed:
1) It is mechanically stuck in the closed position.
2) The ABS brain is malfunctioning and sending 12V via a brown/yellow wire to Pin 86 of the ABS relay even when the bike is turned off.

To tell if the relay is stuck you can just pull it and test for continuity between the 30 and 87 pins. There should not be continuity when it is unplugged. If there is continuity then the relay is stuck closed and needs to be replaced.

To tell if the ABS brain is malfunctioning test for 12V at the 86 Pin of the socket.(Brown/yellow wire.) When the bike is turned of there should not be 12V at Pin 86. If there is 12V then the ABS brain needs to be repaired or replaced.