Re: Battery not charging

Posted by sgtslag on May 10, 2013; 4:46pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/UPDATE-2-Battery-not-charging-tp4039420p4040613.html

Reversing the leads on the meter, reverses the polarity on the Rect./Reg.:  it will only pass current one way, which results in a reading with one polarity, and nothing in the opposite.  Essentially, this test checks the internal diodes of the R/R unit.

You did not mention this, but with regards to running a bike and disconnecting the battery...  Don't!  The battery acts as a load for the Alternator, and without said load, the Alternator, and all of the electricals on the bike, can be destroyed, by a massive surge in current.  This is true for all bikes/engines equipped with a generator/alternator; a magneto system is different.

The DOHC bikes have an electro-magnet system, within the alternator, which produces much more current output than what an alternator equipped with much weaker permanent magnets can ever produce.  It relies on current from the battery to energize the alternator's magnets (electro-magnets), in order for it to generate electricity; without the current to activate the magnets, there is no magnetism, and no electricity generated.

I recommended this book, yesterday, in another thread.  It explains the basics of electrical systems, and troubleshooting, on motorcycles.  It does a very good job of explaining things.  It is worth the money, and the time, to study it.  I am an "expert" in electronics/computers, and even I learned some useful things from it:  Amazon Link.

Based on your description, it sounds as though your charging system is not working:  the bike will run, for a while, off of the battery's stored charge; once that is gone, it won't run at all.  If you discharge the battery to the point where it won't run the engine anymore, it is called "deep discharging" -- this will kill a flooded battery, very quickly, requiring a replacement, no matter how new the battery was...

Follow the manual for troubleshooting the charging system (checking the alternator's rotor, as mentioned already).  If you don't get the specified results, the manual should tell you what to fix/replace.  Once that is done, you can put a known good battery in the bike, and connect your Voltmeter across the battery's leads, then rev the engine up to 3,000 RPM:  it should show ~14 Volts across the battery, if the entire charging/regulating system is working properly.

Here's a simplified breakdown of the electrical system:

A)  Alternator generates AC voltage/current (three phase, three yellow wires).

B)  Rectifier converts said AC into DC (Black/Green wire:  negative, or ground, same thing in this circuit; Red wire:  positive; most of the electrical components on the bike require DC, not AC).

C)  Regulator (contained within the Rectifier unit) keeps the Voltage from climbing too high, which would burn out the lights, the solid-state ignition system on DOHC engines, and the Battery (would boil off the electrolyte, destroying the lead plates within -- new battery needed, very quickly).

D)  The DC current/voltage runs the lights, the horn, the alternator's electro-magnets, the ignition system, the sensor (oil pressure), and it charges the battery without destroying it.

Cheers!