New Factory BMW Battery Issue K75 S - K-Bikes.com - Excellence in Motion
 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old Aug 21st, 2009, 10:22 am Thread Starter
Noob
 
Join Date: Apr 2008
Location: SCARBOROUGH, ME, USA
Posts: 29
Question New Factory BMW Battery Issue K75 S

Have a 1990 K75 S with 25K on it and I just put a new OEM BMW battery ($160) in it a month ago. It has gone flat (voltage dropping 2 volts or more) 4 times since installed. The alternator is charging at 13.35 V at the battery, all connections are clean and tight. If I don't leave it on the tender it will go flat in 4-5 days tops. I've checked the voltage before going for a ride with it fully charged and come home a few hours later and it will be down .5 volts in that time. Anyone had this happen to them ?
MEJETSKI2000 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old Aug 21st, 2009, 2:27 pm
Addict
 
Join Date: Mar 2004
Location: , , UK
Posts: 3,750
Quote:
Originally Posted by MEJETSKI2000
Have a 1990 K75 S with 25K on it and I just put a new OEM BMW battery ($160) in it a month ago. It has gone flat (voltage dropping 2 volts or more) 4 times since installed. The alternator is charging at 13.35 V at the battery, all connections are clean and tight. If I don't leave it on the tender it will go flat in 4-5 days tops. I've checked the voltage before going for a ride with it fully charged and come home a few hours later and it will be down .5 volts in that time. Anyone had this happen to them ?
Suggestions:

1. You should check first if there is a current draw when the ignition switch is off. You cannot fault your new battery until that check is done.

2. That charge voltage may be ok for a near fully charged battery, but if the battery is so flat the starter is sluggish I'd have expected something over 14 volt from the alternator. Try putting the low and high beams on with the engine running at 2-3K rpm. If you see around 14 volts across the battery the alternator is probably OK. If you see 12 volts then it isn't taking care of the load.

All batteries will settle to 12 volt if you leave them standing without charge or tender.

The best test of whether a battery has lost charge or not, is the battery terminal voltage whilst the starter is being cranked. Once it drops below 9-10 volts the battery has insufficient capacity.



Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!
voxmagna is offline  
post #3 of 8 (permalink) Old Aug 22nd, 2009, 7:06 am Thread Starter
Noob
 
Join Date: Apr 2008
Location: SCARBOROUGH, ME, USA
Posts: 29
After topping it off yesterday I checked the voltage and it was 12.96 V, this morning it was down .4 volts, which seems excessive to me. I'm going to double-check all the wiring connections as I saw a bit of rust on the negative lead where it connects to the motor. Probably wouldn't hurt to check the starter lead also I guess. The dealer said they'll load test it for me but I'll check the obvious stuff first so I don't look too stupid if it turns out the battery is ok.

Last edited by MEJETSKI2000; Aug 22nd, 2009 at 7:12 am.
MEJETSKI2000 is offline  
Sponsored Links
Advertisement
 
post #4 of 8 (permalink) Old Aug 22nd, 2009, 8:07 am
Addict
 
Join Date: Mar 2004
Location: , , UK
Posts: 3,750
The most obvious thing is to check the current drain first with th key off. That might tell you something about:

Addons taking power.
Alternator diodes/regulator faulty and causing current drain.

If the correct charge is going in (you don't know) or with the key off it's coming out (you don't know), then you cannot prove very much about the battery.



Never pay again for live sex! | Hot girls doing naughty stuff for free! | Chat for free!
voxmagna is offline  
post #5 of 8 (permalink) Old Aug 22nd, 2009, 9:19 am Thread Starter
Noob
 
Join Date: Apr 2008
Location: SCARBOROUGH, ME, USA
Posts: 29
I'll re-test the alternator per your suggestion with hi-beams on. Bike has no add-ons and has never had any previous electrical issues in 10 years I've owned it. I'll also check how far it drops when I crank the engine. Hopefully it'll point me / us in the right direction.
MEJETSKI2000 is offline  
post #6 of 8 (permalink) Old Aug 22nd, 2009, 5:11 pm Thread Starter
Noob
 
Join Date: Apr 2008
Location: SCARBOROUGH, ME, USA
Posts: 29
Alternator fine, but I have a dead short to ground reading full battery voltage thru the ground circuit. (DVOM between negative terminal and cable).

Started pulling fuses and when I pulled the turn signal fuse the voltage dropped to .02V, about what I expect the clock and ECU to draw. Time to test switches.

Last edited by MEJETSKI2000; Aug 22nd, 2009 at 5:34 pm.
MEJETSKI2000 is offline  
post #7 of 8 (permalink) Old Aug 25th, 2009, 5:18 am Thread Starter
Noob
 
Join Date: Apr 2008
Location: SCARBOROUGH, ME, USA
Posts: 29
Meter reading didn't change when turn signal switches or starter relay unplugged. I assume that means the switches aren't the issue. Meter didn't change when I unplugged the alternator leads (not running) so I suspect that means the diodes are fine,output measured at 13.7V under load at 3K rpm. Not sure where to go from here, except to pulling other relays and see what happens.
MEJETSKI2000 is offline  
post #8 of 8 (permalink) Old Feb 11th, 2010, 5:17 pm
Noob
 
Hangar5's Avatar
 
Join Date: Sep 2009
Location: Gilbert, South Carolina, USA
Posts: 1
Hey
I just stumbled onto this old thread..kinda late with an idea..but my clock was killing batteries on my 87 K75. I had a hard time believing that a digital clock was knocking down a battery. but the amp meter didn't lie. I pulled the pin and velcro'd an old timex over the window. Sorry so late..
Hangar5 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the K-Bikes.com - Excellence in Motion forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
K1200GT battery, starting bonafidebob K12/1300GT (Next Gen) 9 Sep 9th, 2008 3:25 pm
Visit to BMW Factory in Berlin taxswami Ride Tales 2 Dec 11th, 2007 7:47 pm
BMW North America Sells Motorcycle Division??? tedshred Bike Talk 2 Apr 1st, 2007 7:41 pm
Cincinnati BMW Owners screwed by dealer hans471 K1200RS/GT (Classic) 22 Feb 26th, 2006 11:25 am
All BMW Track Day @ Buttonwillow Ca03K12gt Southern California 0 Oct 22nd, 2005 12:52 am

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome