any Electrical Gurus out there?

[Tom Walker]

I have built a Harley special, without room for a normal Harley sized battery. I have to use a small gel type. The charging system works, just too well! The headlight is too bright and blows bulb after a while. The battery overcharges and gets hot. I am using a Zodiak solid state regulator. The engine is a 1970 something Shovelhead.

Can anybody suggest a way forward? thanks, Tom.

[mark2]

try connecting it to a standard battery and see if it is still the same , 70s shovel over charging is rare , they had lots of problems with the rect/reg unit along with the silly two pin plug at the front , most of these problems are caused by a poor earth on the unit , im not sure about the gel battery and I take it you have the kicker conversion  in place 

[Tom Walker]

Thanks Mark. I can see the sense in doing that to check if regulator is working. If it is, is there any way of reducing the alternator output? Maybe fit some kind of resistance?

[mark2]

what are you reading across the battery now ?

[Tom Walker]

Start with charged baattery. No great draw cos I kick it. (ie one accel coil) Running for 5 mins still showing 13.5 volts.

[mark2]

try a wet battery and make sure you have a good earth on battery and rect unit , with no load and a fully charged battery the unit should dump in heat the excess , if you have a ammeter you can see this , I am not keen on the gel batterys but some are and I can see why they are used , one gave me a problem on a velo with a dynamo

[Tom Walker]

Thank for that. I have tried 2 different regulators and the result is the same. I suppose the fact is that the alternator has to do some work, so the energy has to go somewhere. I was hoping there could be a clever electrical gizmo which would switch off the alternator when its not needed. Probably asking the impossible!

[mark2]

the rec/reg unit dumps unwanted amps in heat via the sink (alloy case) it must have a good heavy earth

[chaterlea25]

Hi,
Your problem of the battery heating is caused by the rate tha alternator /rect/reg is charging it
Small batteries need slow/low  charging rates
An alternator will stuff all its energy as quickly as it can into the battery till the voltage reg activates
So you have mismatched battery / alternator
Is the alternator 2 wire output or 3?
It may be possible to install a blocking diode on one phase of the alternator ??

HTH
John

[mark2]

this sounds right but would the ret/reg still try to charge a fully charged battery , why does the system not balance via this unit , if is all working as should and a ammeter fitted I would expect to see a very small charge with a fully charged battery and no other load

[Tom Walker]

Thank you both for your suggestions. I am not an electrics man. As you say, mark2, I dont understand why the regulators I have used (they are what I call "solid state", ie little black boxes with cooling fins, not tins with points and coils in!), dont apply charge, then sense a full battery and stop charging. Its obviously not as simple as that, for some reason, they dont "recognise" the fully charged state of the small battery.

Chater, if you have a possible solution with a" blocking diode on one phase of the alternator", please could you give me more information as to how I do that in practice? Im not afraid to have a go. Please check back, I will go and find some specs on the alternator.

Meanwhile, in basic terms, the alternator is one of those which has magnets in a "flywheel" rotating around several small static coils. The alternator output is 2 wires.The regulator has those 2 going in, and one coming out to the battery. The unit has to be earthed.

Thank you for your help.   

[Tom Walker]

Sorry if this is long winded. After trawling around for an hour, this chap seems to know what he's talking about. It may help if you are kind enough to bother reading it...

"The alternator on cars have a three phase stator. Harley's have a single phase stator. The Harley's regulator puts out a pulsed DC voltage. Without a battery the ignition system can't work. The stator on a harley puts out a AC voltage when the magnets on its rotar spins around it. Several times per revolution its output either +, - or zero.
The regulator on a Harley first limits the peak AC voltage by shorting out anything it doesn't need to maintain the output voltage. This is why it has cooling fins and gets hot. It then uses a bridge rectifier in the reg to convert the regulated AC into DC.

There are several ways a harley charging system can take a shit.

1. The stator shorts out. Disconnect the two wires coming out of the primary and using an ohm meter see the is continuity to ground.
2. The stator is open. Check for continuity between the two wires.
3. The magnets come unglued from the rotor. Check stator voltage while the bike is running it will read low, also the engine will have a strange vibration.
4. The regulator has a shorted SCR. you can spot this one from the smoke it produces while the engine is running.
5. The regulator has a shorted output diode. This one will make the regulator melt and burn the wire going to the battery. It keeps on smoking until the bat is dead or the wire burns into.
6.  The regulator has a SCR that failed in the open mode. Lights burn out and the battery overcharges.
7. The regulator has a diode that fails in the open mode. The battery goes dead after awhile."

Tom.

[mark2]

has the unit your using got 4 wires comeing out so it can be used for poss or neg earth , also is it suited to 6v and 12v , these have a small loop wire at the back and I think are for 6v unless the wire is cut , then they are for 12v or the other way round as mentioned in the fitting instructions , it maybe the case you are running off the battery only and there is no charge from the alt , this will make the battery hot as it goes flat , flatten the battery (leave the light on for a hour) start the bike and see if the lights go brighter when the bike is reved , if not the alt and rect/reg are not working

[Tom Walker]

Its a 3 wire unit, made for Harley alternator models, so can only be for 12 volts. It must be charging, because the headlight is much brighter when its running.

[mark2]

brighter then blows , take a read here it may help but sounds like the rec/reg is shot , http://www.electrosport.com/technical-resources/technical-articles/how-motorcycle-charging-system-works