Overcharging

[TIM1954]

When I rev my cb750 k2 it goes up to 17.5 volts when checking with a multimeter across the battery. Does this mean the regulator is faulty?

[Bryanj]

Is it original or electronic replacement? Could just be a bad connection to reg

[TIM1954]

Original stator, regulator and rectifier that has done 11500 miles.

[taysidedragon]

The original regulators are adjustable.  I would look at that first.

[Bryanj]

They are BUT before playing with it check the voltage on the black wire at the reg to earth, it should be same as battery votage(check with ign ON but kill switch OFF) if its low you will get an overcharge as the reg thinks the battery is low.

If the volts are ok it is possible that the moving contact inside the reg is stuck in one position, carefully remove the reg cover and check contacts.

In Ashs dropbox is an explanation of how the 3 phase charging works

[TIM1954]

Checked the voltage of the black wire from the regulator and it is 11.4 when  battery is 12.7. Is my regulator toast or can it be adjusted? Thanks for your replies.

[Bryanj]

You need to check and clean all the connections from battery to regulator, that is too much of a voltage drop.

After that recheck charging volts then check contacts inside reg before condeming if charging still excessive

[TIM1954]

What should the voltage drop be?

[taysidedragon]

What should the voltage drop be?

As little as possible.  Sounds like you have a poor connection on that cable.

[Bryanj]

Drop should be an absolute max of 0.5v and that is a bit high.

Start with neg of mutimeter on neg of battery and pos on battery take reading

Move neg probe to engine and reading should be same, if not clean up all earth points.

Put neg back on battery then follow the power path checking at multiple polts
1 other end of main power lead(solenoid)
2 input to fuse box
3 output of fuse box
4 into ignition switch (red) up to this point ignition can be turned off
5 output of ignition switch (black) from now on ign switch on, kill switch off
6 black mutipoint in headlamp shell
7 follow on along black back to regulator, do this checking at every connector block or bullet.

At some point on this trek you will find a volt drop BUT  it may be lots of little ones adding up so try and cure even the little ones.

Polish the bullets and the spades then use dielectric grease if you can get it, vaseline will do in a pinch

[Martin6]

Mine had lost its cover on the fuse box. All my electrical woes went away (slight exaggeration) after I cleaned each fuse holder.

[Skoti]

Had the same overcharging problem.

Checked and cleaned connections for signs of voltage drop, then adjusted voltage regulator to correct overcharging.


No matter what I done there always seemed to be a 0.5v voltage drop between battery and regulator.

So I ended up fitting a micro 4 pin relay with a direct feed from the battery to the regulator to overcome the voltage drop.
The relay triggered by the regulator white wire when the ignition is switched on. Edit (should read black wire)

Became so obsessed I also fitted a volt meter.

For photos please click the link below

https://photos.app.goo.gl/GQUC6TZKV9SkJBCh9

[Bryanj]

Dont see how triggering with white wire will work as no power to white till power on black

[Skoti]

Bryan,

Just checked my notes and realised I done the modification during June 2022 and since forgot which way I connected things up. So thanks for correcting me.


The relay trigger wire is indeed the black one with the original green and white regulator wires remaining in place.

So for anyone wishing to do this mod here are the connections from my notes:-

Relay Pin Number connections:-

30  direct feed from battery (via inline fuse)
87  new regulator black wire (live when switched)
85  earth
86  original regulator black wire (used to trigger relay)


This eliminates voltage drop caused by the fuse box, ignition switch and connectors etc


hope this helps






 

[Bryanj]

Sounds like a good mod, maybe tie it into the kill switch to give full volts at coil as well