K75 battery and/or electrical problem

[OfficerImpersonator]

In a development hopefully unrelated to the cooling system issues I've described in another post, I stalled my bike in stop and go downtown traffic last night and the bike wouldn't restart. Seems the battery was discharged to the point where it wouldn't run the starter. I could hear the fuel pump energize when I pushed the start button. The lights and other electrical accessories all still worked as well.

Luckily downtown Seattle is very hilly, so I was able to point her down a hill and roll start the bike. I drove the 20 miles home and parked the bike. I immediately tried to restart the bike once I got home, but the same problem reappeared - my impression is that the battery just doesn't have the amps to turn over the engine. A couple of hours later, after I did some unrelated work to the cooling system, the bike started just fine. This morning, after sitting over night, the bike barely started. Again the battery didn't seem to have the amps to crank the engine.

I've added a fair amount of electrical equipment to the bike in the last five months (driving lights, heated gripadditional horns, headlight modulator, and LED Hyper-Lites). I'm wondering if all this additional current draw is too much for the alternator to both power the equipment and recharge the battery?

I'm thinking about picking up a battery tender to keep the battery at full charge. Does anyone else have any guesses as to what's going on here?

Having just identified the cause of a cooling system issue and facing repairs to a leaky radiator, I'm not terribly excited about having another issue to troubleshoot and repair. Will a battery trickle charger solve my apparently weak battery and/or alternator problem?

[Motor31]

Hard to diagnose from what you have written.

To check the alternator you'll need a multimeter. Charge the battery then start the bike. At high idle or better check the voltage at the battery. It should be 13 volts or better if it's charging. If it's 12 volts the alternator is not charging or not charging enough. Eliminate all loads that you can and check then if it is up, add loads until it drops again.

Definitely get a tender or other battery charger and top up the battery regularly once the problem is found.

[OfficerImpersonator]

How do I best connect the battery tender to the bike? I have a BMW accessory outlet just below the fuse panel - is this a good place to connect the tender to the bike's electrical system - or should I connect it directly to the battery, as I would a car battery trickle charger?

It seems it would be easier to "plug 'n charge" instead of trying to fit alligator clips onto the battery terminals...

[kasteiner]

I have a '91 K100LT and had a similar problem.

I rode in a parade after very little riding for two months. I stalled, could not start, then a friend helped push start it. Later that evening, I had to roll start it again.

My battery is only 1-2 years old so I didn't think it was time for a replacement. I put the battery tender on it, charged the battery and have not had any problems with a low battery since that time (about 4 months).

A battery tender is a good investment. With the expensive problems I hear are caused by a dead battery (when trying to start the engine), and the "close encounter" that you have I have experienced, it's good to keep the battery at full charge.

My battery tender simply plugs into the BMW accessory plug located on the side, below the seat. It works great - makes it easy to put it on the battery tender.

Keith

[OfficerImpersonator]

Sounds like that's what I'll do. Too bad the BMW dealer is on the way home from an outing we have planned for this afternoon :)

[PGlaves]

Will a battery trickle charger solve my apparently weak battery and/or alternator problem?

Nothing in your description leads me to conclude that a plug-in-the-wall charger will solve the problem. You rode the bike 20 miles and the system still wouldn't start the bike. So unless you carry the charger and a long extension cord with you and always park by an outlet someplace - a charger won't fix it.

I'm suspicious: you said it wouldn't start hot but later started cold. How hot?

Starter motor too hot?

Bad connection - loose hot, tight cold?

With the bike cold read voltage at battery. Turn on key. Read voltage at battery. Run starter. Read voltage while cranking. Run engine. Read voltage at idle, and then at2500 or 3000 rpm.

You should be seeing something in the mid 12v range key off. You should be seeing something over 13 running at 2500 rpm.

I have never seen a K bike alternator failure that didn't light the warning light. Airheads will do it with a bad rotor, but I've never seen this on a K bike.

So, unless the bulb is burned out, or the light actually is on while running - I would think the battery is probably bad. Best guess long distance with no tools in my hand.

[PAULBACH]

Try to go back over all that electrical gear you added and check all connections for tightness and connectivity. One bad, or worse an intermittent electrical issue, can be a real headache.

Floating grounds used to be a nasty issue but that was in radio. But it might be worth a try.

Good luck.

[OfficerImpersonator]

I just bought the BMW branded battery charger at my local dealer. Even if it doesn't fix this problem, there's nothing wrong with keeping the bike on a tender.

I'll see how this impacts the problem and if it doesn't fix this issue, I'll be back here comiserating.

[OfficerImpersonator]

Plugged the BMW brand battery charger in yesterday. Discover this morning that my accessory outlet is apparently "dead".

So I connected a pigtail directly to the battery. (included in the kit is the BMW accessory plug, the pigtail, and alligator clips).

I'd prefer the convenience of using the accessory outlet to charge the battery. Someday I might want to power something off of the outlet, so I guess it's another thing for the "to do" list.:banghead

[PAULBACH]

Had the same problem with a "dead" outlet on my K-75. Once I found and replaced the fuse - all worked just fine. But the pigtail is a better idea since it leaves the accessory plug free.

[37071]

Is it possible that you are experiencing the dreaded dirty starter armiture? Try putting the bike in gear and rolling it forward a few inches. Then try the starter button again.:confused:

[OfficerImpersonator]

Had the same problem with a "dead" outlet on my K-75. Once I found and replaced the fuse - all worked just fine. But the pigtail is a better idea since it leaves the accessory plug free.

Just for fun I pulled the ignition coil cover and discovered that the accessory outlet had never been connected to the electrical system.

I learn something new every day!

Now that the charger is connected directly to the battery, she starts just fine after a couple of hours on the tender. Course, that results in a nice little puddle of green fluid beneath the bike from the leak in the cooling system once the engine heats up, but that's a different thread on this forum. :banghead

[Motor31]

Did you check to see if your charging system is putting out enough voltage?

[OfficerImpersonator]

Did you check to see if your charging system is putting out enough voltage?

I'm taking the bike to my wrench for a new radiator tomorrow and I'm going to ask him to check this issue for me.

The issue has completely disappeared since I started using the battery tender, so I think/hope it was a cumulative effect of cold weather affecting the battery and large electrical loads partly due to the cold dark winter weather (heated grips, driving lights, etc.).

But I'll have a final answer tomorrow, and I'll share it with the thread.

[jpeck]

I had a similar intermittent problem with my K75, which turned out to be a bad connection in the ignition switch. I disassembled the switch, cleaned, and reassembled with lots of dielectric grease and it solved the problem.

If you have a wiring diagram and a multimeter, you can check the operation of the switch. I did not see anything wrong with mine, except dried grease.

[From MARS]

If your battery has sat in a discharged state, it may have "sulfated". The plates in a battery are coated with lead. When the battery is discharged, some of this lead falls to the bottom of the cell and reduces the battery's ability to hold a charge. A simple test of the specific gravity of each cell will reveal if this is the case. If you have a maintenance-free battery, a "load tester" will be necessary. I have spent many years working on yachts and we run into this all the time. The batteries will indicate 12.8 volts in a static condition, but when a load is applied, it drops to the 8-9 vdc range. The only cure is a new battery.