Hello folks, been having a little trouble with charging my battery. Have taken some voltage readings. Replaced the voltage regulator as the alt seems to be doing its job. Voltage increases with rpms. Cleaned all the ground and connections. I have read that it needs to be at 14.1 or better to charge? Then I have seen where these numbers aren't bad. I had the battery die on me recently. Luckily I was at the house. Put on battery tender and it took a charge. Haven't taken it out after doing these things. I do normally keep it on the tender. do you guys think the next step is to have the battery checked? Kind of confused. 

With key off 12.59 
At 3500 rpms 13.56 
at idle(900-950) 12.20

Is your bike's electrical system stock, or is it modified (for example LED charge light, new aftermarket gauge cluster)? Do you get a charge light when you first turn on the ignition? Does the charge light extinguish once you reach 2500 or more RPM? Does the charge light remain extinguished once it goes back to idle?

fishboy316 wrote: I had the battery die on me recently. Luckily I was at the house. Put on battery tender and it took a charge.

A battery tender will not charge a discharged (dead) battery sufficiently. Tenders are used for keeping a charged battery from discharging significantly.

Robmack: It appears to be stock. Charge light comes on. It does go out at 2500 and stays out. At least I haven't seen it come back on. Laitch: This was actually a 2 amp trickle charge. Should I hit it with the big charger? Just checked and the battery is still sitting at 12.69 in the off position.

This thing was attached to the blue wire in line. Do you guys know what it is? I took it out and connected the blue wire straight through as I haven't seen anything that looks like this thing in any pics i have seen.

It's a diode - BMW part 61311358268

Here's why it's there:

https://www.kforum-tech.com/Downloads/K100-service-bulletins-and%20special-tools/2354.pdf

12.69V at rest is an almost fully charged battery.  The normal resting voltage is usually 12.8V.  You are only 1/10 of a volt low. 

Is this reading right after you disconnect the battery charger?  What does the battery voltage look like after you turn on the ignition and headlight for a couple seconds?  If it stays above 12.5 - 12.6V the battery should be close to fully charged. 

Are you sure you don't have LED's in the cluster, specifically in the battery idiot light?  Normally, the battery light should go out at just above idle.  Having to rev to 2500 rpm sounds like the alternator isn't getting enough current to excite.  Could be a LED, a bad regulator or possibly worn brushes.

Voltage alone does not tell you if your battery is good.

You should take the battery to an auto parts store and ask them to load test it. (It's free.)

An LED won't cause issues as long as you rev it enough to make the lamp go out. I've been running LEDs for 15 years in numerous Ks without issue.

You just need to rev it to 2,000 RPM to wake up the voltage regulator. (At least for the 50A alternator.)

Starting a cold bike with LEDs:

Thanks for the help!

.75 : This was after 3-4 hours off the tender. With lights on around 12.5. I will look more closely at the cluster when I get home.
Duck: Thanks for the explanation! I will put it back.

Test the diode before you put it back to make sure it is intact.

If you are seeing 12.5 volts at the battery with the ignition and lights on but not running the engine, I would say the battery isn't bad. 

Of course, you can pull it out to have a load test done, or you could measure the voltage while the starter motor is running.  A good battery shouldn't go much below 11.5 volts when the starter is cranking.  If it does, then pull it for a load test.

Good suggestion .75. I will do that.

Thanks
Bill

On "tenders" and battery maintenance: if you do have a slightly weak battery, one that's unable to take a charge from a battery maintainer-type of charger due to its voltage being lower than the threshold for the charger to pick up the battery connection to begin to charge, use a 6V/12V charger and start off on the 6V side until it gains enough voltage to then allow you to switch it over to the 12V side where it may begin to fully charge. Of course, having a battery get that weak means it's likely on its way out anyway - that's not always the case - but you can often get a battery back to at least useful for a spell.

I have an Odyssey PC680 that was a warranty take-off from a police bike - given to me in 2014 due to a swollen case - that I use a shop battery to this day which has dropped to 7 or 8 volts a coupla times after hard use. It'll still start a bike, run an accessory air pump, and is used as a 12V source for testing, etc. Its static voltage is 12.6 as I test it right now and loadtests (Midtronix) as good.

A footnote: my Big Block K100/K1200 has no instruments, or diodes of any kind added, which starts, runs, and charges at 14.4 volts. Excitement enough?! It has had a 9amp (lasted 5+ years) and now 12amp li-ion battery fitted.

Had load test done and battery is good. Tested the charging system and the max is 13.1v at 3500 rpm. Have replaced the Voltage regulator with a new one. Have a tested used 33amp coming. Will take a chance on it for the money. I think I will take a shot at rebuilding this one.  Will have a spare then.

Thanks For the help!
Bill

Well, this alternator is giving the same results, almost exactly. Battery 12.6 off 12.45 running.. Charging 12.55 loaded. 13.19 unloaded. Pulled the dash and not led for the charging light. Tried 3 different voltage regulators. Same general readings. Not sure what direction to go on it now. Tried shaking the chicken bones over it by to no avail!

Have you changed or are you using the same earth cable from the gearbox to the battery.
 I would look there first .

Dont foget that the regulator requires a good earth  .. at current to do its job 

A lot of us have upgraded the earth cable   over the years    ... in just wondering if there is some losses in what you have fitted

The other thing to mention is that the alternator connection cover is undoable   meaning that you could probe the output of the altrrnator directly ...on volts  on the big spade connector   and also on the blue wire ... field feed cable  to see if there is an issue with the wiring somwhere.   Which sounds cinsistent with what your experiencing ,?

Hope that helps   
Good luck

Hey Charlie. What did you upgrade to on the ground wire? Getting 13.4v on the red at 2500 rpm. 12.45 at idle on the blue wire. 12.50 at 2500 rpm. I am not liking the looks of the positive side wire either.
Thanks
Bill

Hey folks, I pulled the connection off on the alternator and measured14.5v up to 15.01. Looks like the alternator is working. Do the connectors come apart? If so could you explain the process?
Thanks

where are you measuring the earth at ...  frame or battery ?

just try measuring again at the main earth point ...and then at the battery for the earth side 

could give you a different answer ?

If the instrument cluster alternator light shuts off after rpm reaches 2500 and stays off regardless of rpm until the engine is started again, as seems to be indicated in post #4; if the alternator appears to be charging the battery at a sufficient rate; if the battery is holding its charge sufficiently to start the engine after a few days of idleness; then what is the problem here? Revving an engine to 2500 rpm shouldn't bother it.

Is the failure to conform to standard values—despite all other appearances of a fully functional charging system —the only concern here? I'll admit I've been distracted lately because the 7 miles of mud between me and firm road surface have receded and I've been riding out in April for the first time in 12 years.

Hello Laitch, glad you got some ride time in!  What I am seeing is that the alternator is putting out14.5 up to 15.01 with the connector pulled from the alternator I never see this or close at the battery. Only getting around 13.1 -13.8 max at the battery. At idle it's about11.7  Have found that the positive cable is cracking and the negative has been messed with. Battery switch off 12.49.
Thanks for checking this out.
Bill
I decided to check at the volt meter and only got 10.9. Don't know if it makes any diff or not but seemed weird.

The problem is that I took it to work for a couple of days without putting it on the tender. Parked in front of the house when I got home. Came out to move it and the battery was flat. Am trying to find the cause.
I plan on some over nighters and really would like to figure this out. Won't always be able to plug it in.
What is the range for 2500 rpm supposed to be? And idle.
Thanks

fishboy316 wrote: Came out to move it and the battery was flat.

First, you should repair or replace your primary battery cables, then you should consider replacing your battery after you've investigated every single angle because it doesn't seem like you need another voltage regulator, but try to do it before gasoline is banned by promotors of Big Electricity and their minions so you'll have fuel to run it.   There is no need to spend a mint on a new battery. This one lasted me ten years and I don't know how long it was in the Brick before I bought it. I just bought another for slightly less  than the price in that ad, with shipping.

I never used a battery tender or charger on it. The Brick is my main transportation for six months or so then it gets stored for six months after its battery has been charged up by a long ride and its battery's ground cable has been disconnected from the transmission. The Brick is stored in an unheated shop where winter temperatures can fall into the low double digits Fahrenheit.

In the spring, I bolt on the ground cable and the moto starts and away we go, if the mud has receded.  

fishboy316 wrote: The problem is that I took it to work for a couple of days without putting it on the tender. Parked in front of the house when I got home. Came out to move it and the battery was flat. Am trying to find the cause.
 I plan on some over nighters and really would like to figure this out. Won't always be able to plug it in.
What is the range for 2500 rpm supposed to be?  And idle.
Thanks

When the ignition is switched on the charge light illuminates as it has a path to the frame via the regulator and the coil in the rotor. The bulb allows a small current to be fed to the rotor coil through the Blue wire to magnetize it ( the bulb  limits the flow of current to a low value). When the engine is turning the whole system becomes self sustaining.  The engine RPM has to be at or around 2500 RPM to make it self sustaining. The rectifier feeds DC electricity to the regulator and in turn the electromagnet on the rotor. The voltage at D+ balances the voltage being fed from the battery and the bulb has the same voltage on either side of it. As the voltage is equal on both sides of the bulb no current can flow and the light goes out.

What is very strange is your battery tests strong yet is dies in a couple days without a tender.  You seem to have a parasitic current draw on the system when the ignition is off, which shouldn't happen on an '85 RS. The only current draw on the system with the ignition off should be the clock, and it is a couple mA.  Has the PO installed something on the bike that connects to the battery directly?  If you have a multimeter with a current reading capability, put it in series with the battery positive cable with the ignition off.  See if there is any appreciable current being drawn from the battery (above 10-15 mA).

Looking for parasitic current draw.....I had one occur in a flasher relay. The relays are permanently live.

Thank you gentlemen. I  am going to try to look at the suggestions this evening. Perhaps tomorrow eve. The only things I see are something called fuel saver I believe it is called, connectors for tenders,  and some driving lights. I will look around for anything else and report back. 
I have had issues with the charging system before on this bike. Had to replace a battery about 10 months ago. Was at Del Marva bike week with my Harley buddies...Of course! It just went flat in the middle of the street. Shut right down. I had ridden 2 hours down there before this happened. Replaced the battery and have kept it on the tender since for the most part. Come to think of it the battery that went flat at bike week was only about 7 months old. 

Thanks again.
Bill

fishboy316 wrote:I have had issues with the charging system before on this bike. Had to replace a battery about 10 months ago. Come to think of it the battery that went flat at bike week was only about 7 months old.

If I'd only known that 25 posts early; so many precious moments have slipped away.

The mind is a terrible thing to waste. Sorry.   I have managed to procure a cable in good shape. Also went out this evening and for the heck of it decided to throw the load tester on the battery and now it is saying soh 0 replace. I think the friggin thing is haunted! What the heck would eat new 2 batteries in 1.5 years?

"So many precious moments have passed" 

fishboy316 wrote:The mind is a terrible thing to waste. Sorry.   I have managed to procure a cable in good shape. Also went out this evening and for the heck of it decided to throw the load tester on the battery and now it is saying soh 0 replace. I think the friggin thing is haunted! What the heck would eat new 2 batteries in 1.5 years?

"So many precious moments have passed" 

What batteries have burned up? (Brand and amp-hours.)

The WestCo 12V20P is a good battery for Ks.

https://www.amazon.com/gp/product/B074VFKRKL

fishboy316 wrote:I think the friggin thing is haunted! What the heck would eat new 2 batteries in 1.5 years?

robmack has provided a method to start determining that in post #25.

The Town of Stowe, VT has started a contest wherein the entrants submit the day and time the first tractor trailer will be stuck between the cliffs on the road through Smugglers Notch—a mountain route that truckers are instructed to avoid by means of flashing lights, giant warning signs, and four figure fines plus towing costs.

Maybe in your contest entrants can guess the source of current drain and win a battery case autographed by you. It seems you might have a few of them.

Laitch wrote:

fishboy316 wrote:I think the friggin thing is haunted! What the heck would eat new 2 batteries in 1.5 years?

robmack has provided a method to start determining that in post #25.

The Town of Stowe, VT has started a contest wherein the entrants submit the day and time the first tractor trailer will be stuck between the cliffs on the road through Smugglers Notch—a mountain route that truckers are instructed to avoid by means of flashing lights, giant warning signs, and four figure fines plus towing costs.

Maybe in your contest entrants can guess the source of current drain and win a battery case autographed by you. It seems you might have a few of them.

 Yes It would be my pleasure to autograph one up! I am starting a pile in the corner of the shed, an expensive pile!

Other questions....

do you have an alarm on it

did you add a USB outlet

did you add a radio?

fishboy316 wrote: Yes It would be my pleasure to autograph one up!

I'm guessing replacing the primary battery cables and using a battery with no history of frequent, complete discharging will earn me your autographed case; however, in reviewing posts, I realized you've been using chicken bones to cast restorative spells on your electrical system. Actually, what your gris-gris bag should include is a black cat bone. I searched this site for instructions about obtaining one but there were none found. Simply put, it'll be the only bone that remains floating after the skeleton is dumped into the pond at midnight. Bring a sandwich and coffee; it could take a while.

robmack has provided detailed instructions—beyond what are in this thread—on how to find mysterious sources of current drain. You could read them here. Also, typing parasitic drain in the Portal's search window will give you pertinent reading when sitting around the burn barrel awaiting midnight.

Laitch wrote:

fishboy316 wrote: Yes It would be my pleasure to autograph one up!

I'm guessing replacing the primary battery cables and using a battery with no history of frequent, complete discharging will earn me your autographed case; however, in reviewing posts, I realized you've been using chicken bones to cast restorative spells on your electrical system. Actually, what your gris-gris bag should include is a black cat bone. I searched this site for instructions about obtaining one but there were none found. Simply put, it'll be the only bone that remains floating after the skeleton is dumped into the pond at midnight. Bring a sandwich and coffee; it could take a while.

robmack has provided detailed instructions—beyond what are in this thread—on how to find mysterious sources of current drain. You could read them here. Also, typing parasitic drain in the Portal's search window will give you pertinent reading when sitting around the burn barrel awaiting midnight.

 AHHHH! Forgot the black cat bone! There happens to be a black cat in my neighborhood that keeps sitting on a blind curve that I could probably get one from very soon!

Thanks for the information Will crank up the burn barrel.

I unfortunately don't have time to go back through this thread, so if this has already been mentioned, so be it.  It is very likely that you have a parasitic current draw that is discharging your battery.  A battery will be damaged when it is discharged deeply and not recharged soon after.  I suspect that is what is destroying your batteries.  RBM has given you a process for troubleshooting parasitic drain.  That is you path to happiness.

The stock wiring is usually pretty good, it's the added stuff that causes problems.  Have you been into the relay box and looked for any non-original wiring?  Did you get under the tank and look for any suspicious wires spliced into the wiring there.

These are the two most likely places for owners adding extra goodies to their bike to butcher the wiring.

Thanks .75. Just finished reading robmack's post. Will be digging into it this evening.

Thanks again.

Can you confirm if you added a USB outlet at any time?

No Sir, Mr. Olaf. I did not. The  only thing I have added was some leds on the tail end about a month and a half ago but this has been going on since I got it. The original battery was toast. The first replacement was toast in Sept. The replacement for the replacement is toast now. They seem to last about 7 months.

Thanks

Do you have a permanent charging adapter attached across the battery, into which you can plug your charger?  I have a CTEK smart battery charger which has a quick connect cable that is supposed to be fastened to the battery terminals.  That adapter cable has. a built in LED that shows me the charge level on the battery but I found that the LED would deplete the battery after a couple months if I didn't continually use the bike.  Do you have something similar?

You mention something called a "Fuel Saver".  What does it it do?  Does it have a display?

I vaguely recall there was a device that was able to display things like fuel remaining, range to empty, MPG, etc.  I think it had connections to the injectors, speedometer and a few other things.  Is this correct?  Can you post a photo of this device?

Regarding RBM's advice to check for parasitic current draw, I would suggest the following test:

Remove all the fuses from the fuse holder on the side of the relay box.  Inspect the bike for any additional fuse holders that may have been installed with auxiliary equipment.  If you find any, remove those fuses as well.

Disconnect the positive cable from the battery and connect your digital meter between the end of the cable and the positive terminal on the battery.  Set the meter to read "ma".

With the ignition key "Off" observe the reading on your meter.  It should be 0.0ma or very close to it.

Now add fuses one at a time while checking the meter reading each time you add another one.  The only ma you should see is for the clock, and the draw for that should only be something like 2.0ma or less. 

If you see the current draw increase, note which fuse caused it.  We can use that information to further isolate the problem. 

BTW, how many wires are connected to the positive terminal on the battery?  If there are additional wires connected to it, measure the current draw on them separately from the main cable.

just a question '
'you know there is a small tab ...erm finger that connects to the bottom of the regulator ...on a small about 7mm flat section which is an    reference .

the finger is usually tinned on the last centimeter where i connects to the regulator and is quite visible with the regulator out .
i seem to recall that after replacing brushes ...a long time ago ..i assembled the regulator and fitted to the bike , i checked operations after and i got some verry wierd results 

i removed the regulator and bent the finger back to where is should be , touching that section ...wallah  problem solved .

just a thought

Point-Seven-five wrote:I vaguely recall there was a device that was able to display things like fuel remaining, range to empty, MPG, etc.  I think it had connections to the injectors, speedometer and a few other things.  Is this correct?  Can you post a photo of this device?

The product name is FUEL Plus. Like the factory clock it drains the battery and takes a little more juice than the factory clock but per the Fuel Plus manual that I have it takes a month or more for it to drain a battery.

Battery drain during storage
FUEL Plus uses more current than the clock it replaced. If you store your bike for more than a month the current drain can be reduced by removing and immediately replacing the fuse (third down under left side cover) for the clock. Have the display on one of the main functions when removing power. The interruption in power causes it to stop. Be sure the fuse is in place during storage to retain the memory. FUEL PlusTM will blank but maintain the fuel data. The clock will not run. When you turn on the ignition FUEL Plus will start and TM display the clock, flashing 12:00 to remind you to set it. You do not have to start the engine to set it when it flashes

Thanks, Duck!  Good information. 

Still, Fishboy needs to find where the battery is losing it's charge.

Hello Gents, Update: I replaced the neg cable on the battery with no change. I have a positive cable coming today or tomorrow. The pos cable is not in great shape so hopefully this will help. Did the parasitic draw test and the only thing I saw was fuse 3 at 0.1ma. All others were 00.0. One more thing I found was the battery is not bad. The terminal screw I was clamped on was loose.   

robmac: I do have a connector on it but there is no LED. Also thanks for the great instructions for testing the draw. Made it easy!

.75: It is actually FUEL plus. I have not done anything with it. It is the the only parasitic draw I have found. 0.1. There are 2 additional connectors on the + terminal. Tested and no additional draw.

Charlie: I tried bending the connector and no change.  Was worth a try!

Duck: That's what it is. 

I am leaning toward the + cable. It has cracked insulation and wire showing. I am also going into the relay box and cleaning all the connections. Will be inspecting all the wires. 

So can anyone tell me what voltage I should be seeing at the battery at 2500 rpm and at idle 
(950 rpm). Just general idea.

Thank you guys for all the patients and help

Bill

Well after losing what little bit of hair I had I believe she's fixed. At 2500 rpm I am getting 14.12v load tester says charging is normal. I had doused the alternator connector with Deposit D5 and didn't see a change. It sat for 2 days an poof I am getting 14.12. Wooo-Hooo! I have cleaned most of the connections now a it seems happy. Battery tests great now. Seems to be holding steady. Load tester says soh 100%. CCA normal at 400. I have learned a lot about the charging system and now have a couple of spare parts. Also have a little jump box to carry on the bike.

I want to thank you all for helping me through another BMW crisis! And a few laughs laitch If we ever meet I owe you all a cold beer! Or 2
Thanks again!
Bill

Deoxit saves the day.  ...again!

Point-Seven-five wrote:Deoxit saves the day.  ...again!

Bill was likely referring to his inhaling DepoxIT, a nasal spray that eliminates the desire to buy more Bricks. He's  running low on free time.

oh.

K-pox killer. There is a k75 not far from me that's up for sale and not a hateful price. Have been considering a looksee... Please pass the inhaler.