Topic: Charging system question

[Lost and Confused]

I have a 74 Cb750k. After working on it for 18 months, I can only get it to charge about 13 volts. Is this low?. I have replaced the following:


Battery
Fuse box  (blades)
Harness (twice)
Stator
Headlight
Rectifier   ( Oregon products)
Regulator  (Oregon products)
Electronic ignition  (installed)
New 3ohm coils
New plugs (iridium)
New spark plug wires
New aftermarket ignition switch
New right hand control
New harness from stator to main harness.
All grounds checked and checked
New headlight
All bulbs are new
Starter selinoid and starter are not new. They work fine

I'm stumped. Electrics are not my strong suit.

Thanks, Bob

[flybox1]

"You can adjust the for a max output of 14.7v"  right from their site.

[Black 750K8]

I have a 74 Cb750k. After working on it for 18 months, I can only get it to charge about 13 volts. Is this low?. I have replaced the following:


Battery
Fuse box  (blades)
Harness (twice)
Stator
Headlight
Rectifier   ( Oregon products)
Regulator  (Oregon products)
Electronic ignition  (installed)
New 3ohm coils
New plugs (iridium)
New spark plug wires
New aftermarket ignition switch
New right hand control
New harness from stator to main harness.
All grounds checked and checked
New headlightAll bulbs are new
Starter selinoid and starter are not new. They work fine

I'm stumped. Electrics are not my strong suit.

Thanks, Bob

What size bulb? Why did you go with 3 instead of 5 ohm coils? Is the regulator adjustable?

13 volts at what rpm and was the battery fully charged when you took your readings? Did you see a increase as you brought the rpms up? TT has a excellent post in the FAQ under electrical.

[lucky]

I have a 74 Cb750k. After working on it for 18 months, I can only get it to charge about 13 volts. Is this low?. I have replaced the following:


Battery
Fuse box  (blades)
Harness (twice)
Stator
Headlight
Rectifier   ( Oregon products)
Regulator  (Oregon products)
Electronic ignition  (installed)
New 3ohm coils
New plugs (iridium)
New spark plug wires
New aftermarket ignition switch
New right hand control
New harness from stator to main harness.
All grounds checked and checked
New headlight
All bulbs are new
Starter selinoid and starter are not new. They work fine

I'm stumped. Electrics are not my strong suit.

Thanks, Bob

If the battery is already charged up, it will not charge more.
The 12V battery at rest with engine off should be more than 12V when fully charged.
See a 12V battery has 6 cells and each cell is 2.3 -2.7 volts so 2.3X6=13.8 volts but we call it a 12V battery anyway.

When the engine is running make sure the headlights are on and then see if it is charging.

[Lost and Confused]

Thanks guys. Black, I have a Pamco ignition, and 3 ohm can be used. When I rebuilt, I tried  to take in all manufacturers requirements and suggestions. Have put far to much money in it thus far. If I sell, it'll be at a loss.


Thanks for letting me vent


Bob

[TwoTired]

It is important to know if you are measuring the battery after charging it from a source off the bike before checking the charging system.

A lead acid starting battery can be charged safely to 14.5V.  But at that point the charging rate should be reduced.  A battery charged and then rested for two hours should stabilize at the 12.6V to 12.8V range.

When on the bike, it matters at what RPM the charge voltage is measured, as the alternator output falls to about 1/3 of max at idle vs. full output at 5000 RPM.

Technically measuring 13V at the battery means it is not depleting, even if not accepting charge very fast.  Our bikes do normally deplete the battery at idle speed and then recharge it while driving about.  This makes the battery voltage variable depending on what state the battery is in at the time of measurement and the speed of the alternator RPM.

Automotive charging systems provide ALL the power needed to operate the machines and usually do charge at idle as well as higher RPMs, and maintain the battery at right around 13.8V.  The battery is generally needed only when operating the starter motor.

Stock SOHC4 need the battery to keep spark alive during idle.

Know that the battery charge state dominates the voltage measurement, NOT the charging system.  For example, if the battery were totally depleted, the voltage would be about 10V.  The charging system should raise that voltage.  But, it will do so slowly.  It may well reach the peak of 14.5V, but it could take 10 hours at 5000RPM to fully restore the battery to full status.

So, measuring the absolute instantaneous battery voltage, does not take into account the transitional nature of this bike's electrical system, or which way the system is trending up or down.  13V could be a way point on its way to a higher voltage, or a way point on its way to a lower voltage.  And the trend information is important to know as well as the current operating condition.

If you toss a ball from one hand to another, it travels in an altitudinal arc.   Stating the current altitude in transition does not tell you if it ascending or descending or if it has reached the apex of the arc.