Topic: 78 CB550K Battery Issue

[sokolikp]

I'm just learning how to troubleshoot and perform maintenance on my bike. I recently used the forum to help me re-solder the connections on the back of my ignition switch, but now I have a new (and probably related) issue. I recently bought a multi-meter to test my connections, and now I need your help with where to look.

I have been taking my bike out for extended rides on the weekends, and by the end of the day, once the bike has been sitting for a few hours, my battery is dead. I assume the issue is either a bad battery or a short circuit. It also sounds like I need to confirm that it's not a regulator/rectifier issue.

I confirmed that my alternator is working correctly - when I rev the engine the voltage increases from ~13V to 14V+. I just charged my battery using a trickle charger to ~13.17V. This seems to be the max charge (charged for about 18 hours). I'm going to let the bike sit uncharged overnight and check the voltage again tomorrow. What should I expect to see if there is a short circuit vs. a battery that isn't holding charge? What's the best way to test the two separately? I'm trying to knock potential issues off the list one at a time. I'm very new to this, so it will take clear explanations and a bit of patience.

Thanks for the help.

[calj737]

Depending on the type of battery (lead acid, AGM, LiFe) you will see different stored volts. At a minimum, you should have 13.2, closer to 13.8 for LiFe.

There's lots of possible drains on your electrical system even while riding. What is the wattage of your headlight? Has someone replaced it with a non-stock unit not rated for your bike? You should definitely check all your grounds for bare metal contact, no corrosion.

Here's a good systematic approach for checking your entire electrical system to help you out:
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

[TwoTired]

Lead acid and AGM batteries will not have 13.2 volts unless being charged or is immediately off the charger and retaining a surcharge.  A fully charged and rested for 2 hours lead acid battery will have 12.6-12.8 Volts.  This measurement doesn't mean it is good, just not bad.  It must also pass a load test to be proclaimed good.

There are many charger designs.  I have some that will charge to 14.5V, and then switch itself into maintain mode and 13.2V level, others a bit higher.

LiFePo4 static battery voltages are different than lead acid tech.


Anyway, these batteries don't store electricity.  Electrical energy is either consumed or expended by a chemical conversion process.  Electrical measurements are derivatives of the process.  To know the actual storage level, you measure the specific gravity of the electrolyte.

[sokolikp]

That flow chart is great, thank you. I'll start running some diagnostics and report back here with questions.

[Muckinfuss]

Going forward, you may want to examine getting your hands on one of the newer technology chargers for Lead and AGm (no lithium!) that pulse the battery using a sensor logic. It begins with an automatic test mode and will tell you immediately if the battery has sulfated or shorted past the point of no return.  Battery Tender started the game, but there are others.

[TwoTired]

If by "pulse charger" you mean the anti-sulfation scheme of sending power spikes to the battery, the only has a effect (limited) on single cell batteries, at best.  The 12v batteries that we have are 6 cells in series.  The cells themselves have very high impedance (resistant to voltage level change), so any pulses are flattened right out at the very first cell in the series.  So, at least 4 cells simply can't receive any benefit from a pulses in the input terminals.

On the other hand, if the charger uses a "chopper" scheme to provide variable pulse width power to the terminals, that is fine. The battery cells will accept power whenever the pulses are higher than its present level state, and increase charge level based on the average voltage value provided.

I have a Yuasa Charger that detects if the battery can increase its voltage with starting input pulses and then checking the voltage held between pulses.  If the battery can increase its voltage level, the charger assumes the battery is functional and proceeds to the next steady power phase of charging.  This charger refuses to charge a deeply discharged but otherwise good battery, as it's internal voltage sense doesn't fall within it's accepted parameters.  A short but quick charge with an old dumb charger, brings the V level up to where the Yuasa charges as it normally would any partially depleted battery.

[sokolikp]

Ok, so I let my bike sit for one day after a full charge and took the reading last night. On Sunday afternoon/evening when I unplugged the battery from the charger, I was seeing a charge of 13.17 V. Yesterday (Monday) night, I had a reading of 12.68 V (without turning key on). Once I turned the key to the ON position, but charge went down by several tenths of a volt (I believe this is to be expected). I'm not sure if anything can be deduced from the fact that the voltage went down by almost 0.5 V overnight while sitting cold.

I tried the to test my charging system using this diagram [http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf]. When I revved to 2500 RPM I read higher than 13.5 V. When I continued to rev higher, I read a voltage of high 14 and even into 15 V, but once I hit 5000 RPM the voltage went back down to about 14.8 V. From the diagram, I know I should expect 14.8 V at 5000 RPM, but it doesn't say if it's an issue to see a higher voltage between 2500 and 5000 RPM. Is that a problem?

Assuming it's not as issue, where's the next place I look to figure out why my battery is draining? I forgot to check what type of battery I have, but I'll be sure to do that tonight. I'll check the contacts with the leads and make sure there's nothing loose or corroded.

When I re-soldered my ignition switch, I had to remove the headlight to get to the part. In doing so, one of the nuts on the inside of the headlight came unglued and fell into the middle of the compartment. I had to take apart the headlight, re-glue the nut, and make sure it stayed in place when I screwed in the bolt on the outside of the headlight compartment. Does any of that sound like something that could have impacted the battery? I wasn't having the battery drain issue before I re-soldered the switch (my bike would just turn off at random!).

[sokolikp]

Also, here is a photo of the bike from earlier this summer.

[TwoTired]

Have the coils and ignition system been "upgraded"?

You should learn at what point (RPM the charging system takes over the electrical load of the bike.

You'll note that at idle the voltage falls below 12.6V., which indicates the battery is discharging.  When you rev it, the voltage will come back up, even if a bit slowly.   This is normal, you do NOT want the battery voltage to swing above 15V or below 11V rapidly as this would defeat the purpose of the battery, or indicate a bad battery.

Once you learn of this break point or critical RPM, you will know as you ride when the battery is discharging and when it is charging.  If you spend more operation time discharging than charging, the battery will deplete.  Normally you have to keep the RPM in the "charging" RPM 6 times longer than when in the discharging mode in order to keep the battery full.

This assumes a bike in stock configuration.  Lighting and other electrical system "upgrades" easily alter that 6 to 1 ratio.


It is also possible that your wiring, connectors, fuse clips and switch contacts are not only wasting power made by the alternator, it may prevent the alternator from making full power, by reducing the voltage its field coil receives.  The field coil produces a magnetic field whose strength is determined by the voltage fed to it.  Reduce the field strength, and the alternator max output reduces.

[sokolikp]

This is really good info, thank you. I'll find the break-point RPM and be cognizant of the 6:1 ratio.

So are you saying I should check my wiring, connectors, fuse clips and switch contacts, or that I should check the field coil (or both)? If it's the former, where do I start? Do I work from the battery and move towards the ignition system? Is there a rule of thumb to know if I have a bad connection/wiring?

If it's the latter, I've read a few threads on here about how to check the coil. That being said, if you have any documents on steps to analyze the coil it would be much appreciated.

[TwoTired]

Know how to use a multimeter?

Set it to volts. ~20 scale if your model has that.  lower if possible.  Place one probe on the Battery POS terminal, and the other probe on the black wire connection to the Vreg.  Start the bike and turn everything on.  Note the voltage reading.  This is the loss you bike's wiring contributes to you charging woes.

You should also repeat this test with probes on the Battery NEG and the green wire at the Vreg.   The two measurements are added to find out how much your bike is lying to the vreg about true battery voltage.


The FAQ has a post about checking coils.  But, you could tell us if you have points and if your coil leads are molded into the coil body.  If so, they are stock and the primaries will be ~5 Ω.  The stock spark system won't result in a battery charge issue.

[sokolikp]

Great, I just bought a multimeter over the weekend and it's getting good use. I'll check all of these in the next few days.