Topic: Up to 18v to the battery, and the regulator works. What's wrong?

[Kristoffa]

Hi!

I had a problem with the headlight bulb blowing, and as soon as I replaced it, it happend again.

My battery reads 12.5 at idle, but the more I turn the throttle, the higher it goes. To above 18v. From reading on the forum it seemed like the most common problem was the regulator. I took this off, and followed the maintenance steps in the manual. Put it back on the bike, and got the same result.

One of my friends have the same bike, so I borrowed his regulator to make sure my regulator was the problem.

I measured the voltage on his battery, the values were normal 12.5-13.5. When I installed the regulator on my bike it gave the same results as with my old one, 18+ with high RPMS. I placed my regulator on his bike and it gave normal values. 12.5 - 13.5

I'm a rookie when it comes to the electrical stuff on my bike. Would really appreciate if anyone had some good tips for what I should check.

Bike: HONDA CB500K3 1978

[strynboen]

its the viring to the regulator..regulator need a good kontakt to the battery..to" feel" the state of load..if that konnektion are bad..the regulator "think" the battery are very low..and fire up the loading to a" to heigh" load

so klean all vires up..and try to get a volt reading at the regulator (Black) vire... there is so close to battery voltage as possibel...often there is some differens1-2 volt lost somhvere in the viring or main key area
the regulator is feed bu the main key..so thek voltage up there too often korodes the taps at the back side.behind the key

[Jerry Rxman Griffin aka MuthaF'er]

The stock regulator is supposed to dump 'extra' voltage to ground if it is working correctly.

[strynboen]

not realy..iys the Kawasaki permanent magenet system doing that..they make power all time..and throv the not used  back in the frame..shorting the stator aut..erly Hondas use it too cb 77 andcb 450/500 twin and others.
.but not the sohc modells

.Honda,s  sohc do cut the power to the elektro magenet..and turn the stator off..so it not make restistins to the engine vhen it not are used..
permanent magenet systems sucks some pover from the engine even it not make elektric pover. just try to turn a motor and feel hov hard they are to turn

[Bodi]

I agree with strynboen. The usual problem with "boiling battery" is a bad reference voltage to the regulator, if the regulator has been tested OK.
The regulator takes "ignition key on" power (black wire) and uses it for two things: to power the alternator field coil and control alternator output, and as its reference voltage to decide how much alternator power to ask for.
The black wire voltage at the alternator will never be exactly battery voltage, there will always be some voltage drop in the harness wiring, connectors, and switches.
When that voltage drop increases because of corroded connectors and switches or other such problems, the reference voltage gets low enough that - if the alternator can make enough power - the battery voltage goes above "maximum" and damage results.
You want a wet cell battery to be at around 14.5 volts when fully charged with the engine running. Less, and it won't reach full charge. More, and the electrolyte liquid's water is "boiled" off as hydrogen and oxygen gas (not water vapour).
Switch on the bike and have all lights etc on. Measure battery voltage at the battery terminals. Measure again from the frame (an engine bolt head is good) to the battery "+" terminal: This must be almost exactly equal to the battery terminal measurement - within 1/10 V or so! If not, check the battery ground ("-") cable to ensure it is in good condition and has an excellent connection to the frame. Once the ground is good (if it wasn't) measure from the regulator black wire to frame. This should be within 1V of the battery measurement (recheck battery voltage at the same time as the battery will be draining while the key is on).
The Problem - if the battery is at 12V and you measure 9V at the regulator black wire, the regulator will be trying to get that 9V up to 14.5V... if it can manage that, the battery will actually be a 17.5 volts and overcharging (boiling dry).
One option is to clean up the harness connectors and switches to minimize voltage drop. Another is to add a relay with its coil from black to ground switching battery "+" terminal directly to the regulator terminal for the black wire, this will give the best reference voltage and alternator performance (the field coil powers from that regulator terminal, and more coil voltage = more alternator power output).
It is possible that the alternator field coil has been miswired and gets full voltage all the time, with the regulator doing nothing. Or the regulator is bad. Or you've used a more modern regulator not designed for the OEM wiring.

[riffman12]

Another is to add a relay with its coil from black to ground switching battery "+" terminal directly to the regulator terminal for the black wire, this will give the best reference voltage and alternator performance (the field coil powers from that regulator terminal, and more coil voltage = more alternator power output).

sorry to hijack here, but do you have any detailed instructions on how to wire this system with the relay? I'm having the same problem as Kristoffa

At the moment I wired the black directly to the battery positive and it killed my battery because I didn't have a relay.

[Kristoffa]

Thank you for the help strynboen, I'll check the wires

[Kristoffa]

Thanks for the description of steps Bodi, really helpful.

[Bodi]

detailed instructions on how to wire this system with the relay?

The field coil draws around 5A so a automotive horn relay (usually 40A rated) will work. Usually these have DIN wire numbers as referenced below. I don't think I've seen one that doesn't, but #85 & 86 are the relay coil, #30 and 87 are the form A SPST NO (normally open) relay contacts. #87a, if you have it, is the NC contact of a form C SPDT relay... not what you want to use as #87a will put the regulator on with key off, and off with key on.

Remove the black wire from the regulator. Connect it to relay terminal #86. Connect terminal #87 to ground. Check that the relay clicks when you turn the key on.
Get an inline automotive fuseholder with a 10A fuse, the little square plastic fuses are better than the glass tube kind. Also a 1/4" ring crimp terminal that fits the fuseholder wire. These fuseholders usually come with a loop of wire, cut it fairly close to the fuseholder so the short wire end will reach somewhere close to the battery "+" terminal and out of the way you that can tuck the fuseholder. You want as short an "unfused" wire as possible: if it shorts to the frame - there's no fuse - it will burst into flame. Disconnect the wire at battery "-" and pull it away so it won't touch the battery terminal until time to reconnect it. Connect the fuseholder wire to battery "+" with the ring terminal and tuck away the holder.
Hopefully the other fuseholder wire is long enough to reach where you put the relay, extend it if not. This wire, fused battery power, goes to relay terminal #30. Connect terminal #87 to the regulator power input (where the black wire was).
Reconnect battery "-" wire.
Test (meter or test light) that it works properly - the relay clicks and the regulator power goes on when the key is on.

[scottly]

its the viring to the regulator..regulator need a good kontakt to the battery..to" feel" the state of load..if that konnektion are bad..the regulator "think" the battery are very low..and fire up the loading to a" to heigh" load

I think the wiring fault is a bad connection to ground on the regulator green wire, not the battery + side of the "feel". The stock regulator defaults to connecting the black reg wire to the white field wire, until the current flow through the reg coil from the black supply wire to ground opens the field circuit. No ground reference and the voltage climbs the same as if the white field wire is connected directly to battery +.

[strynboen]

yes ..it can be on both sides.the power needs 2 konnektions to flow..a ground pullls the same power then the positive(..but a small part goes transformed to heat on the vay through..so a littel loss can be faund)

[riffman12]

detailed instructions on how to wire this system with the relay?

The field coil draws around 5A so a automotive horn relay (usually 40A rated) will work. Usually these have DIN wire numbers as referenced below. I don't think I've seen one that doesn't, but #85 & 86 are the relay coil, #30 and 87 are the form A SPST NO (normally open) relay contacts. #87a, if you have it, is the NC contact of a form C SPDT relay... not what you want to use as #87a will put the regulator on with key off, and off with key on.

Remove the black wire from the regulator. Connect it to relay terminal #86. Connect terminal #87 to ground. Check that the relay clicks when you turn the key on.
Get an inline automotive fuseholder with a 10A fuse, the little square plastic fuses are better than the glass tube kind. Also a 1/4" ring crimp terminal that fits the fuseholder wire. These fuseholders usually come with a loop of wire, cut it fairly close to the fuseholder so the short wire end will reach somewhere close to the battery "+" terminal and out of the way you that can tuck the fuseholder. You want as short an "unfused" wire as possible: if it shorts to the frame - there's no fuse - it will burst into flame. Disconnect the wire at battery "-" and pull it away so it won't touch the battery terminal until time to reconnect it. Connect the fuseholder wire to battery "+" with the ring terminal and tuck away the holder.
Hopefully the other fuseholder wire is long enough to reach where you put the relay, extend it if not. This wire, fused battery power, goes to relay terminal #30. Connect terminal #87 to the regulator power input (where the black wire was).
Reconnect battery "-" wire.
Test (meter or test light) that it works properly - the relay clicks and the regulator power goes on when the key is on.

did this to my bike this weekend - looks like it fixed my overcharging issues. Thanks for the details, Bodi. Only I think you had one typo - 85 goes to ground, not 87.

I'm getting 12.5 V at 1000 RPM, maxing out at 14.4 V

Are there any negative long term affects of this setup?

[strynboen]

is it possibel to do the mod..so the ignision coils get delevry from the same relæ.
.so they get full 12 volt(they need to be in line vith the kill svitch/..so there is a problem to use the same relæ to both..you vil turn off the load system use safty stop buttom...
is there a vay to korrekt this problem

[riffman12]

I'm not really sure how this affects the coils. I'm still learning exactly how the electrical system works on these bikes, but I'm sure someone else can chime in on that.

[strynboen]

yes ...let"us vait for the expers to blow that idea up

[Lilxt]

Hum damn why haven't i thought of using a relay.. I have the same problem but only a 1 volt drop on the black wire.. Love this forum!