A Relay alternative?

I think I may have a bad stator.

From my research, I find the output is below what is maybe needed to keep my battery fully charged. Could be my last violent intersection with planet Earth compromised the integrity of the stator. Maybe it is 29-year-magnetic decay. But the result is the same. Lack of capacity to keep up with demand.

I started noticing a problem right after I installed the Dyna triggers. I attributed the occasionally discharged battery to the battery age, occasional extended storage, and the fact that I have an H4 55 watt bulb burning all the time.

The problem became obvious after I installed the coil relay modification. I don't know what the additional demands are of the relay coil, but current demands (no pun intended) seem to have overwhelmed my alternator output.

Here is what I have done:

New battery.

Overnight charging of the same while out of the bike.

Tested, and found that the battery charges better when I take the headlight out of the circuit. It goes to mid 13, but starts dropping when the light is on at the same engine rpm.

Here is what I have thought about.

Running without headlight. (bad idea)

Going back to points. (bad idea)

Removing relay. (bad idea)

Swapping out the coil relay for something that draws less power. Anyone know what resistance should be on the relay coil? Maybe I have one that is drawing too much.

What is the possibilty of using a solid state relay for the coil modification?

I guess if I was sure it was faulty I could replace the stator. But I would rather eliminate other things first. This wouldn't be as much of a problem if I could swap in a known good stator. But I'm not sure such a thing exists if they are all old like mine.

Thanks in advance.

:lol:

Wouldn't having a coil mod and relay actually help the overall charging system, by taking out the long route through the switch and small wire system, thus removing a load?

If you measure the voltage at the battery at idle, and then again at 4500 rpm, what readings do you get? Do it with the headlight on and off.

The relay draws about 0.1 amp. That's not an issue.
If you are still using the 4-ohm coils, the Dyna S is using an extra 3 or 4 amps at idle (that's double of the points setup). The relay mod will use more current since the extra voltage allows extra current to flow in the ignition. (But the same would happen if you replaced all the wiring and eliminated the relay. and it's not extra-voltage, really, it's just full, normal voltage.)
If the headlight is the same wattage as the original, then it's not using a lot more current than the original, unless Halogens somehow use more current at lower voltages than a normal incandescent.

I just went through this on an old Honda. It had me baffled since everything appeared to work, but there was somehow an extra current draw. I told my buddy the only possibility was that the ignition was somehow using extra power. Sure-enough, we looked under the points cover and there was the Dyna S.

Post edited by: loudhvx, at: 2007/05/17 13:02

Maybe I can help, I've been an EE tech a long time and some of you guys need a quick lesson.
1. Relay coils usually draw very little current, so it shouldn't cause a loading problem
2. Ignition coils DO draw a lot of current (low resistance increases current draw)
2. WATTS is a measure of power consumed NOT brightness, 55W is the product of voltage X current (approx. 5 Amps)So a 55W bulb of any type will draw the same current.
3. Small wire has MORE resistance than thick, (just like a small pipe carries less water than a large one), so therefore it will limit current because it becomes a significant element in the voltage drop of a circuit. This will cause the lower voltage at your coils or load, especially if the circuit draws a lot of current (current is like the water pressure). A circuit will drop all of the total voltage across all of its series elements (wires,lamps, coils, etc) whatever is in the circuit. The smaller wire has more resistance therefore drops more voltage, lowering the usable voltage to whatever you're powering. When your wires get hot you are exceeding the current carrying capability of that gauge of wire, it becomes a "heating element" and gets hot. So if you can use larger wire to the coils it will help reduce this voltage drop.
Hope this helps explain some of it. I hope to be a regular contributor to this forum, especially to the electrical.
Thanks! Good Luck!

Maybe I can help, I've been an EE tech a long time and some of you guys need a quick lesson.
1. Relay coils usually draw very little current, so it shouldn't cause a loading problem
2. Ignition coils DO draw a lot of current (low resistance increases current draw)
2. WATTS is a measure of power consumed NOT brightness, 55W is the product of voltage X current (approx. 5 Amps)So a 55W bulb of any type will draw the same current.
3. Small wire has MORE resistance than thick, (just like a small pipe carries less water than a large one), so therefore it will limit current because it becomes a significant element in the voltage drop of a circuit. This will cause the lower voltage at your coils or load, especially if the circuit draws a lot of current (current is like the water pressure). A circuit will drop all of the total voltage across all of its series elements (wires,lamps, coils, etc) whatever is in the circuit. The smaller wire has more resistance therefore drops more voltage, lowering the usable voltage to whatever you're powering. When your wires get hot you are exceeding the current carrying capability of that gauge of wire, it becomes a "heating element" and gets hot. So if you can use larger wire to the coils it will help reduce this voltage drop.
Hope this helps explain some of it. I hope to be a regular contributor to this forum, especially to the electrical.
Thanks! Good Luck!

The coils are what draw power, not the relay. The relay is a switch. There is some inherent resistance on the switch but probably less than the original power path to the coils.

I measured the current to my stock coils last night and total was about 2 amps, so I figure about 12 ohms each (6 ohms equivalent in a parallel connection) so really, the wire shouldn't be a contributing factor to voltage drop in a stock setup. I suppose if lower resistance coils are used then the current goes up and the stock wiring does drop more voltage, but the gauge is pretty large so it's more likely the contact resistance of the switches in the circuit, (ignition & kill switch I think). So a good 30A relay controlled by the ignition switch with heavier wire from the fuse directly to the coils should do the trick, but keep in mind that the relay is another added mechanical device and all mechanical devices will fail, it's just a question of when.
Ride safe!

The Dyna uses double the power of points. That is an extra 40~50 watts. That is usually enough to drain a battery especially if you spend a lot of time in stop and go situations.

You could try a 35W/35W H4 lamp to save some power. The 20 watts might just make the difference.

I just bought one of these for a KZ400 (uses 35W stock).

35W/35W H4 headlamp at Bikebandit

For some reason their photo is really tiny on that link. Here is a bigger photo. Scroll down through their selection to see it.

bike bandit bulb selection

Post edited by: loudhvx, at: 2007/06/27 11:10

KaZooCruiser wrote:

...may have a bad stator...battery charges better when I take the headlight out of the circuit. It goes to mid 13, but starts dropping when the light is on at the same engine rpm....

Thinking mid 13 is below spec.
Is faulty voltage regulator a possibility?

Just for info I checked my 1977 KZ650 that has all 1978 charge system on it and Dyna-s ignition and came up with:
RPM needed to have the stator overcome electrical demands and begin battery charge aprox 1200.
Charge volts at 4000 RPM, aprox 14.8
So it does look like you have a bad stator or reg/rec as 13.5 is low.

Ron, you wrote, "RPM needed to have the stator overcome electrical demands and begin battery charge aprox 1200."

How did you decide the stator was meeting demand? Is that where it makes 12VDC?

I would go through the charging system first, such as checking the rectifier, stator, rotor (if not a permanent magnet), carbor brushes if it has them, etc. first.