Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Charging problem refuses to respond to usual cures

[moto748]

Apologies for yet another boring "charging" thread!. My bike hasn't really been right for some weeks now. While back I had a flat battery at work. Got a jump-start, and got the bike into dock. Stock gel battery was beyond recall (2001 748). Standard Yuasa 16Ah battery was fitted. Alternator and reg/rect both checked and serviceable. Problem was traced to corroded connectors on loom. Connnectors cleaned, 14.5 volts when running, job's a good 'un. Week or so later, flat battery again. Gel battery as stock fitted. Charging voltage re-checked and OK.
Yesterday, drove home from work in car to pick up bike, and it's a no-go yet again.


I should added that my pattern of use is pretty good; the bike is ridden (nearly) every day, and for a decent distance. Had no charging probs in over 60000 miles on Ducatis before.

Seems to me one of two things is happened here. Either the charging voltage indicated "in the workshop" is only intermittent, or there's some large voltage drain on the system.

Anyone got any ideas?

Thanks in advance.

[BTW I ordered one of those LED (LCD?)voltmeters recommended on another thread. Unfortunately the bike didn't last until I took delivery]

[Edited on 6-5-2004 by moto748]

[Shazaam!]

After I mounted my LCD voltmeter I saw some unusual behavior. The battery voltage readout would indicate normal charging voltage for awhile, and then would drop (a few volts) into a net discharge condition.

The wires from the stator to the regulator needed to be replaced. At first, it appeared that the 30 amps being carried by the wire had just overheated a few inches of insulation next to the high-resistance bullet connectors. But, when I removed the common sheath that the wires run in back to the left engine cover, I found that overheating (from the current, not the engine) had softened the insulation to a degree where I could peel it with my fingernail. A multimeter says it's OK but at the higher AC output levels the wires short together. Remember, the wires are touching along the entire sheath length.

I didn't need to remove the engine cover. Inside the engine the wires don't touch each other. The approach that I took was to replace the damaged wiring (with a larger gauge to reduce electrical heating) up to where it exits the side cover. I pushed a piece of shrink wrap tubing over each of the wires and into where they pass through the seal in the cover and left the internal portion of wiring alone since they are separated inside the engine. The main problem is that they touch each other along their length where they run in a common sheath.

I also took the oportunity to relocate the regulator itself.

You can read the full explanation here:

http://ducatisportingclub.com/contro...d.php?tid=2042

[moto748]

That does seem very plausible, shazaam!

I'll get that checked out.

[Nigel C]

do you ride with the lights on ?????

[moto748]

First a big thank you to Shazaam!; the voltmeter arrived yesterday, although I only spoke to them on the phone on Thursday. Fitted it, and it showed up the problem straightaway!

Wasdn't quite the same problem that Shazaam! had, (although he'd have a different alternator to mine on a 916?), but was the rectifier in the end. I've been told that the 3 phase rectifiers seldom give trouble, but this one worked at first, but broke down when hot. Started off at 14V, but soon went down to 12V after a few miles. Replaced with 2nd hand rectifier, and now charges to 14.2V at virtually all road speeds, with lights on! Idles at about 12.6V with lights on, and battery now reads 12.9V with ignition off.

I noticed that there was a small bulge and crack in the back of the old rectifier. Clearly something had broken down inside there.

So I'd strongly recommend the voltmeter, especially to those with the older alternators (that's you weeksy!). It sits very neatly below the temp gauge, just like in Shazzam's pictures.

Well chuffed!

[Shazaam!]

Moto (and everyone else with a superbike,)

I strongly urge you to relocate the regulator from inside the fairing to behind the rear wheel (see picture in my above post). I had five regulator failures before solving the heat problem this way. The regulator simply cannot survive the heat from the header pipe plus it's own internally generated heat. Even out in the airstream it gets almost too hot to touch.

[moto748]

Originally posted by Shazaam!
Moto (and everyone else with a superbike,)

I strongly urge you to relocate the regulator from inside the fairing to behind the rear wheel (see picture in my above post). I had five regulator failures before solving the heat problem this way. The regulator simply cannot survive the heat from the header pipe plus it's own internally generated heat. Even out in the airstream it gets almost too hot to touch.

I take your pont, but unfortunately I don't live in a Californian climate!

I can see the advantage of siting the reg/rect more "out in the open", but I'm not sure it'd survive long in the path of the mud and rain it would often be subject to in a typical British "summer"!

However, today I saw an ST2 where the rect had been sited behind the vee-piece, which had a custom "vent" in it I think I'm right in saying that's not standard?).
My understanding is that the three-phase alternator and rectifier set-up, although not perfect, is generally considerably more reliable than the single and dual-phase set-ups on earlier bikes.
As far as locating the rect is concerned, clearly there's a balance to be struck between ventilation/cooling and weather protection. I can remember the old British Triumph twins, where the so-called Zenor diode (regulator) was sited under the headlight, for similar cooling reasons.

[Shazaam!]

Not to worry. The regulators have effectively a weatherproof construction so wet conditions will help cool the unit. The heatsink housing/cooling fins are non-corrosive aluminum, just like the engine. The electronics are protected by an encapsulating compound material.