1990 K75: Battery Not Holding Charge

[mdk_mdk]

Stock 1990 K75 with 58K miles, pulled off Cape Cod last year, has been running great except now the battery won't stay charged.

I installed a new Odyssey PC680 when I got the bike late last summer. Haven't had any issues till lately when it seems the battery doesn't want to hold a charge. I have the bike on a tender so I suspect that the alternator is not charging the battery. This also seems to have started around the time I changed the monkey nuts on the alternator.

Troubleshooting performed today:

Tested drain on battery by placing multi-meter between the negative terminal and the frame ground, key off: 0.8 on 200 mA multi-meter setting. Should be 20-40 milliamps for clock, is 0.8 too high? Pulled each fuse, no change in reading other than fuse #3 which also turned off the clock.

Checked resistance to ground, negative battery terminal to lower left frame/trans ground, reading was 0 Ohms

I checked the plug on the top of the alternator, connections looked OK, not perfect but not rusty or corroded, I sprayed them with contact cleaner and re-plugged them in. I also pulled the voltage regulator off the back of the alternator, the brushes had about 1/4"-3/8" of spring movement in them. Cleaned the terminal with some contact cleaner and re-installed the voltage regulator.

Charged battery for an hour and started bike: ~12.8V across battery terminals @ 1000 RPM, ~13.8V @ 2500 RPM, no increase in voltage over 2500 RPM

The red alternator light on the gauge cluster works, when I turned off the "choke" too early the RPMs dropped and I saw the light glow red.


Questions:

Is 13.8V enough output from the alternator?  If not, any ideas how to check if it's the alternator or the voltage regulator?

Any ideas how changing the monkey nuts could have caused this? (It's too much of a coincidence that it started not long after changing them...)

Is 0.8 too much of a current draw?

Thanks,
Mark in NJ

[The Mighty Gryphon]

13.8v output from the alternator is about right for running with a low battery.  Voltage will go up slightly as current draw decreases.   It might go as high as 14.1 volts.

The charging light sounds like it is working properly.  The fact that it goes out when the engine is running tells me the alternator is working properly, especially since you are seeing the 13.8 volts.

I would strongly recommend that you pull the battery and take it to a place that can do a load test on it.  Just reading terminal voltage says nothing about the condition of the plates.   

I suspect that somehow, the battery was discharged over the winter and sat like that for a month or so.  That will ruin even the best battery regardless of how old or new it is.

[Laitch]

13.8v output from the alternator is about right for running with a low battery.
I suspect that somehow, the battery was discharged over the winter . . .

+1

At 1000rpm idle, my six year old battery outputs approximately 13.8V and the output climbs slightly above 14V at 2000rpm. mdk_mdk's moto is idling at 12.8. As TMG indicates, discharging is a battery killer. It's so simple just to disconnect the battery ground from the transmission. A fully-charged battery in good condition can winter through temps down to -20ºF  for six months that way then usually start up the moto without further charging when reconnected.

[Past-my-Prime]

2 years. That's been how long batteries last on my bike. Doesn't seem to matter if I leave them on the bike for the winter (where it does get down to -40 where I live and at that temp doesn't matter C or F). If I put on tender: 2 years. If I neglect: 2 years. If I put in basement and rotate charge with all the other various batteries there: 2 years. OEM from BMW: 2 years. Gel Cell: 2 years. Mini tractor battery: 2 years. Finally I'm going with some Chinese made gel cell and will put it somewhere warm for the winter and keep charged but I'm not optimistic. I expect 2 years before I'm buying the next one.

[mdk_mdk]

Thanks for all the replies, I'll get another battery.

[Laitch]

Finally I'm going with some Chinese made gel cell and will put it somewhere warm for the winter . . ..

Put it somewhere cool for the winter—not that it will matter, apparently. :giggles

[The Mighty Gryphon]

Never store a battery with less than a full charge.  Even a 90% charge will let the battery lose capacity during storage. 

Best thing is to run the bike for a good ride before you put it away.  Then disconnect the negative terminal if you are leaving the bike idle until Spring.

I keep my bikes in an unheated attached garage with the batteries in them.  Temperatures in there will get down to -5 F.  About every ten days or so, I'll fire the bikes up and let them fast idle until the fan cycles a couple times, then shut them down.  The $79 ChiCom battery in my K75RT is now 6 years old with 40,000 miles on it and still going strong.  One winter, I left a trickle charger connected to the K100RS for the entire winter(about 5 months) and in the spring the battery was shot.  That battery was only two years old. 

[johnny]

greetings...

east penn manufacturing makes many batteries marketed under many names...

whats you wants is a etx20l... the 20 pounder etx... all east penn brands use etx20 in their part numbers...

you know you gotts east penn when you gotts the red cap and the screws...


product-power.jpg (65.71 kB . 360x543 - viewed 400 times)

my blaines farm and fleet east penn is called duration extreme...


duration.jpg (40.16 kB . 576x576 - viewed 474 times)

its a strong runner in its 4th riding season... garaged in unheated garage on a deltran bettery tender jr... -35 peak this past winter...

i run a voltage meter... im 13.8 no catz xlo and 13.7 with catz xlo while riding tached up... will be at 12.8 to 12.6 after sitting for a few days of untendered nesting...

i have now and or have had 4 of these in 4 different motos... all 4 have been 100%... im thinking you should have the same results if you wanna give it a go...

j o

[mdk_mdk]

Thanks Johnny, I'll check our local Tractor Supply, I think they carry these.

[johnny]

greetings...

this duracell at battries plus is 130 $ which is 40 $ more than in the chee...

east penn has 3 deka stores a half hour away... note... always measure to make sure its gonna fit before buying...


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j o

[Martin]

I've gotten 8 years and 6 years out of the two Deka's that I've run.  The last two times I changed batteries I was unable to source a Deka. The third battery was a Rev Plus which went for 6 years but no longer available in Brick size, so I am now running a Dynavolt. However my brick is running at least 3 times a week and we don't really have much of a winter.
Regards Martin.

[mdk_mdk]

I found this battery, looks just like the one you posted, we'll see how it does.

[The Mighty Gryphon]

Ah, so Everstart from Walmart is made by Deka?  No wonder my old boat batteries lasted through 12 years of the hell I put them through.