Need help on possible battery or electrical problem

[Guest]

Hi,

My son is using my motorcycle while I am away for a couple of months on a work assignment, and he has run into an electrical problem. I am trying to help him diagnose the problem long distance but need some expert help and/or advice.

The problem started when he was at the gas station. He killed and restarted the bike a couple of times to move around the station. When he filled up, he could not turn the engine over, but just heard a slight click once. He then noticed that none of the lights would come on. Nothing. Prior to that, things seem to have been running fine.

He called the auto club for a jump. He was able to start it but could not keep it running when the jumper cables were disconnected. Had the bike towed home.

At home, he tried charging the battery. He was able to get it to the point where the charger indicated that it had a full charge. But when he reconnected the battery, the instrument lights were very dim, and he could not turn over the engine. Tried charging a couple of more times, but the same results.

He tried to use a VOM meter to see if there is a short. Some of the circuits have very low resistance, but nothing definitive.

He then went and purchased a jumper battery, and he was able to get the bike started. Everything was working, lights, turn signals, high beam and horn, even when all were tuned on. When returning the bike to idle speed, the bike continued to run while still attached to the jumper battery.

With the engine running at high rev, he switched to the original battery. At that point (at high rev) the turn signals did not work (relay not flashing the bulbs), and the horn was weak. When returned to idle, the bike died.

Could it be just a bad battery? If so, I will have him buy a new battery. Are the symptoms indicating other possible problems (partial short, bad charging system)?

Any assistance will be greatly appreciated.

[Redman]

not ful;;ly sure what you mean by jumper battery, but I quess you mean just some battery to use that doesnt fit.
I would say if things are better with this other batteryh that is with yhou present battery, well then, your battery is having a problem.

You say you charge your battery, and it still will not turn over the engine. That sounds like problem with the battery.

One quick check of the charging system:
Use your jumper battery.
Measure battery voltage with engine off (mid 12s probably).
THen start engine and measure battery voltage with engoine at mid rpms, 4000 rpm. SHopuld measure higher than it was with engine off, like the upper 13s or maybe low 14s.
More detailed tests to furter troubleshoot in the stator papers.

.

[BassCliff]

Hi,

Have the battery "load tested" at a shop or auto parts store. It might be a bad battery. But the whole charging system needs to be tested too. Have a look at the electrical section of my website for tests that supplement The Stator Papers. You could have a bad battery, bad regulator/rectifier unit, a bad stator, or all three. Test everything before throwing money at the problem.

Have your son clean all of the electrical connections and grounds on the entire bike. I mean everything, fuse box, blinker stalks, all the molex connectors under the tank, grounds, ignition switch connections, etc. The ground wire from the r/r unit should be connected directly to the negative battery terminal. Then re-test.

The simplest tests is to start the bike, rev it up to 4000-5000 rpm, and measure the voltage across the battery terminals. It should be 14.5 volts DC. If it is much less then you have charging system problems.

Some links:

Stator Papers

More On The Stator Papers

GS Charging System Health+Quick Test

Cleaning Your Wiring Harness

Stator Test

Stator Replacement

Regulator/Rectifier Replacement

Thank you for your indulgence,

BassCliff

[pmong]

Redman,

Yes an external battery. It is one of those with a built in charger and are for cars. We had one before some time ago, and we use it for not only jump starting vehicles but also to power 12v equipment. Very handle.

Thanks for the tip. I will ask my son to follow through on the recommended tests.

not ful;;ly sure what you mean by jumper battery, but I quess you mean just some battery to use that doesnt fit.
I would say if things are better with this other batteryh that is with yhou present battery, well then, your battery is having a problem.

You say you charge your battery, and it still will not turn over the engine. That sounds like problem with the battery.

One quick check of the charging system:
Use your jumper battery.
Measure battery voltage with engine off (mid 12s probably).
THen start engine and measure battery voltage with engoine at mid rpms, 4000 rpm. SHopuld measure higher than it was with engine off, like the upper 13s or maybe low 14s.
More detailed tests to furter troubleshoot in the stator papers.

.

[pmong]

BassCliff,

Thanks, we actually have downloaded your references. You site is extremely helpful. We will have another look. I do hope that it is something simple like a bad battery. Otherwise, we will have to work on the other stuff when I get back.

He is using his Vespa as a backup. Not great going up the hills to get back home because it goes very slow.

Also, I should say that I enjoy your videos of your rides around Southern Ca.

Hi,

Have the battery "load tested" at a shop or auto parts store. It might be a bad battery. But the whole charging system needs to be tested too. Have a look at the electrical section of my website for tests that supplement The Stator Papers. You could have a bad battery, bad regulator/rectifier unit, a bad stator, or all three. Test everything before throwing money at the problem.

Have your son clean all of the electrical connections and grounds on the entire bike. I mean everything, fuse box, blinker stalks, all the molex connectors under the tank, grounds, ignition switch connections, etc. The ground wire from the r/r unit should be connected directly to the negative battery terminal. Then re-test.

The simplest tests is to start the bike, rev it up to 4000-5000 rpm, and measure the voltage across the battery terminals. It should be 14.5 volts DC. If it is much less then you have charging system problems.

Some links:

Stator Papers

More On The Stator Papers

GS Charging System Health+Quick Test

Cleaning Your Wiring Harness

Stator Test

Stator Replacement

Regulator/Rectifier Replacement

Thank you for your indulgence,

BassCliff

[Normk]

If I read this correctly, the bike battery will not crank the engine when it has been on a charger for some time.

The bike starts, and idles with the bike battery disconnected but with a jumper battery.

When the jumper battery is disconnected the bike runs until the bike battery is reconnected.

If the above is correct, the bike battery seems to be no good. It would seem to have an internal short which is loading the charging system beyond capacity at idle. Install a new battery.

Bike batteries are strange creatures. We want to believe that they are simply small versions of automotive and truck batteries and disassembling both seems to support that. The correlation fails when one relates failures as I have not seen automotive or truck batteries which failed in some of the ways experienced with bike batteries. It can be difficult to diagnose a failed battery such as yours in the manner in which one would diagnose an automotive battery.

The most conclusive method is to substitute a known good battery. I really hate to admit this as I have both training and equipment necessary to do load tests, sulfation tests, etc. to both bike and automotive batteries but have seen so many examples of the problem.

I have a battery under my work bench which came out of my brother-in-law's 1100 Gold Wing which is a case in point.

AT worst, you will have replaced a suspect battery which will remove that variable.

[pmong]

Norm,

Thanks for the insights. We will look for a new battery.

I guess what throw us is when measuring the battery's voltage. According to my son, the charger "charge complete" LED is on, and when we measure the voltage, it is nearly 13v. However, when attached to the bike, it delivers very little power as indicated by the very faint instrument light when turned on. He did another test that I forgot to mention. When the ignition key is on the "on" position, the voltage on the battery drops to below 5v.

Is it possible for the problem to develop almost instantly, like it did at the gas station? I guess if it is an internal short, but want to get your opinion.

A question. Does he have to buy the exact battery? It is hard to locate the specified batter. There is one from Sears that is slightly taller (5 5/16 rather than 5 1/8). He will check to see if there is enough clearance. It has the same amp hours (12).

Again, thanks.

If I read this correctly, the bike battery will not crank the engine when it has been on a charger for some time.

The bike starts, and idles with the bike battery disconnected but with a jumper battery.

When the jumper battery is disconnected the bike runs until the bike battery is reconnected.

If the above is correct, the bike battery seems to be no good. It would seem to have an internal short which is loading the charging system beyond capacity at idle. Install a new battery.

Bike batteries are strange creatures. We want to believe that they are simply small versions of automotive and truck batteries and disassembling both seems to support that. The correlation fails when one relates failures as I have not seen automotive or truck batteries which failed in some of the ways experienced with bike batteries. It can be difficult to diagnose a failed battery such as yours in the manner in which one would diagnose an automotive battery.

The most conclusive method is to substitute a known good battery. I really hate to admit this as I have both training and equipment necessary to do load tests, sulfation tests, etc. to both bike and automotive batteries but have seen so many examples of the problem.

I have a battery under my work bench which came out of my brother-in-law's 1100 Gold Wing which is a case in point.

AT worst, you will have replaced a suspect battery which will remove that variable.

[BassCliff]

Hi,

That usually means that there's a dead/shorted cell within the battery. It may show good voltage but provide no current.


Thank you for your indulgence,

BassCliff

[pmong]

Additional information, and two questions

Hi,

Again, thank you everyone for your help. My son was able to do the tests on the charging system. I am writing this up for any future reader with the hope that the information is useful. And I also have a couple of questions at the end.

With the jumper battery fully charged, he started the bike. When turned on, the voltage dropped from 13v+ to about 12.5v or so, as expected. When he turned over the engine, the voltage dropped to below 12v, which I think is norm with the additional load from the starter. With the engine running, he rev'ed it up, but the voltage did not increase to 14.5v but stayed around 12v-13v range. This indicated that the charging system was not kicking in. When the battery was disconnected, the voltage fell to 6.2v-6.4v. (Because the bike has no tach, he could only guess the rev.)

The lack of a charge probably killed the battery.

He then did a no-load test of the generator. All showed 75v+ ac, which indicates that the generator is fine. He then did the impedence test of the RR. All pairs showed infinite ohms, that is, no current going through. This would indicate that the RR is completely blown.

QUESTIONS:

One, is it common for all of the diodes to go bad at once?

Two, could a short have blown the diodes?

Thank you in advance.

Hi,

That usually means that there's a dead/shorted cell within the battery. It may show good voltage but provide no current.


Thank you for your indulgence,

BassCliff

[Normk]

First thing would be to use a 12 volt test light to recheck the diodes as meters often give unreliable results unless the meter has a specific diode test function. Even then I have seen problems with using a meter to test.

A 12 volt test light with 12 volt battery is 100% reliable as it duplicates closely the actual conditions. A meter usually lacks sufficient voltage to forward bias the diodes so all will appear as open circuit/infinite resistance.

Others may have also misunderstood your previous post as meaning that the bike continued to run without battery connected. It seems that you have a charging system issue which will be: VRR, stator, rotor magnet, or wiring.

Just spent some time with a couple of VRR, oscilloscope, loads and meters playing with the charging system on my 1979 GS850G but will post to a different thread as some results are strange.

[pmong]

Norm,

Thanks for the advice.

My son will be making a simple 12v test light to assess the diodes. He is planning to use an old light bulb from his Vespa, soldering on some leads, and attaching it to the jumper battery.

Is there anything he should look for? Is it good enough to visually compare the brightness from a closed circuit with the bulb and the brightness when running the current through a diode?

I imagine if one or more of the diodes is not working, then there is a problem with the rectifier. However, if all are working (allowing current through), then does that mean the regulator is bad? Is there a way to test the regulator?

First thing would be to use a 12 volt test light to recheck the diodes as meters often give unreliable results unless the meter has a specific diode test function. Even then I have seen problems with using a meter to test.

A 12 volt test light with 12 volt battery is 100% reliable as it duplicates closely the actual conditions. A meter usually lacks sufficient voltage to forward bias the diodes so all will appear as open circuit/infinite resistance.

Others may have also misunderstood your previous post as meaning that the bike continued to run without battery connected. It seems that you have a charging system issue which will be: VRR, stator, rotor magnet, or wiring.

Just spent some time with a couple of VRR, oscilloscope, loads and meters playing with the charging system on my 1979 GS850G but will post to a different thread as some results are strange.