Nocturnal Electrical Leech

koko64 · February 11, 2016, 03:26:52 AM

Got a 1997 400SS that kills batteries.
Customer has killed two new batteries with a standing bike. I swear they are turning the key too far and turning on the parking lights. They say they check to make sure this is not happening. Bike runs well and then after a week when they try to start it there is no power, not even dash lights. Stone dead and a battery that appears to have dropped a cell or two.

Bike is charging ok with a new battery, voltage at 3000 rpm shows 14V at battery despite the little alternator. No voltage spikes during tests and voltage doesn't drop below 12.5 at idle with the light on (Euro switch). No excessive regulator heat and quite stable voltage when running.

The problem is when the bike is switched off, so I suspect a problem with ignition switch. The bike once blew out the ignition relay and fuse, so I suspect a short from bad ignition switch contacts. Obviously a serious parasitic loss when parked. I will have to go over everything starting with the ignition switch.

Anyone seen this kind of thing before?

ducpainter · February 11, 2016, 03:41:34 AM

Disconnect battery. Put a low wattage light bulb in between a battery lead and the battery. Remove fuses until the light goes out. That's the problem circuit.

Good luck finding it.

Howie · February 11, 2016, 05:05:40 AM

Quote from: ducpainter on February 11, 2016, 03:41:34 AM
Disconnect battery. Put a low wattage light bulb in between a battery lead and the battery. Remove fuses until the light goes out. That's the problem circuit.

Good luck finding it.

Low wattage bulb = test light. Or a voltmeter will work. Pull fuses until the voltage goes down. Unplug the regulator if the bulb is still lit or battery voltage still shows 12 volts.

Speeddog · February 11, 2016, 09:18:45 AM

Had an SS with the battery tender lead ziptied so tight to the frame that it violated the insulation, so a small electrical drain.

<Edited for speeling.>

koko64 · February 11, 2016, 01:03:26 PM

Cheers you blokes.

koko64 · February 16, 2016, 12:47:15 AM

Been checking for parasitic loss per fuse. Can lose 0.5V over 9 hours. A couple of weeks and a new battery is killed. No one fuse is showing. I am doing overnight tests while I do other work on this bike.

Can a regulator be faulty but work fine when charging, but when the motor is turned off possibly shunt off power from the battery due to a problem? That is, work fine one way in only one direction, but be failing in the other, so to speak? I'm starting to suspect this. Also I note that the bike has another type of regulator adapted to it, so I'm getting suspicious.

Howie · February 16, 2016, 03:12:40 AM

Yes, a rare failure but it does happen That is why I suggested disconnecting the regulator if nothing is found with the fuses. Can you measure amperage draw? Oh! Old bike, wet battery. Dirty battery top can be a problem. Voltmeter positive on terminal, negative to battery top you should read 0 volts. Clean it anyway.

koko64 · February 16, 2016, 03:49:05 AM

Thanks Howie. Yep, it was last on my list and it seems to be allowing the battery to sit safe. I'll know for sure in the morning. I need to keep the bike for a week or two to do lots of little jobs on it, so I have been testing each circuit each night. It needs a front guard, chain and sprockets, oil, bolts tightened, carbs cleaned up, fresh hardware, etc, etc.

koko64 · February 16, 2016, 04:28:39 PM

With all fuses in and battery connected, but Reg disconnected I only lost 0.02 V over night and some of that was the battery settling after a quick charge. Battery sat about 13V overnight. So it is the Reg for sure. Was worth checking all the fuses though.
A different reg off another bike mfr was used and wired direct to the battery. A cheap way out converting another reg from the used parts vendors. While this has advantages I think it is more likely to directly bleed off voltage due to a fault rather than going through the loom and being isolated by the ignition switch?
That sound right?

Thinking back, I had similar issues with a direct to battery wired Japanese bike reg on an M944.

Speeddog · February 16, 2016, 06:34:08 PM

I'm pretty sure all Monsters have the Reg connected directly to the battery + terminal, no switch in between, only a fuse.

I may have had a Reg go bad that way once, not sure, but for sure it's not common.

Dunno offhand what voltage the single phase alternators can supply, but the 3-phase ones can supply 100 VAC.
Perhaps it just over-voltaged that Reg.

koko64 · February 16, 2016, 10:21:44 PM

Thanks mate.
Cheers.

Howie · February 16, 2016, 11:05:28 PM

Quote from: Speeddog on February 16, 2016, 06:34:08 PM
I'm pretty sure all Monsters have the Reg connected directly to the battery + terminal, no switch in between, only a fuse.

I may have had a Reg go bad that way once, not sure, but for sure it's not common.

Dunno offhand what voltage the single phase alternators can supply, but the 3-phase ones can supply 100 VAC.
Perhaps it just over-voltaged that Reg.

No switch. The isolation is done with a zener diode within the regulator.

koko64 · February 16, 2016, 11:12:34 PM

I remember those! Had one on me old Trumpy.

Are the ZD's common to Japanese regs or are they used on the older Ducati oem regs? So if the ZD pops you can get voltage shunted to earth when you dont want it?

Howie · February 16, 2016, 11:36:41 PM

AFAIK all AC regulators have some sort of isolation diode.

koko64 · February 16, 2016, 11:44:27 PM

Thanks.
Cheers mate.

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