High voltage!

[Thunzie]

Hi guys, to produce voltage and charge to the battery my XS bobber has the popular mod which many have used to allow for a single reg/rec unit. The particvular reg/rec I'm using is from an XJ600, it's the same unit that was used on a variety of Yamaha models.

As a matter of routine maintenance today I measured the output across my battery terminals with the bike running and it's up around 19.2VDC, with the revs up at about 2500 or more RPM. Shouldn't it be capping out at about 15VDC??

Other info - Recently I had an intermittent short which blew a few fuses and ran my battery level down over abut a week until I found the source of the short and fixed it.

Cheers! -Mark (Thunzie)

 

[vr3506]

Hi Mark,

Using this rect/regulator, the alternatorbrushes must not have a earth contact, as the early altrnatortypes have! (they have black and green wiring than) You should have the brusholder with the 2 same type brushes. they are wired brown and green, as also on your unit. The XJ unit does in fact the same, it's much cheaper to get while there is no XS 650 mentioned,

Jan

 

[Thunzie]

Hi Mark,

Using this rect/regulator, the alternatorbrushes must not have a earth contact, as the early altrnatortypes have! (they have black and green wiring than) You should have the brusholder with the 2 same type brushes. they are wired brown and green, as also on your unit. The XJ unit does in fact the same, it's much cheaper to get while there is no XS 650 mentioned,

Jan

Hi Jan,

Yes, I'm aware of the unearthed brushes requirement, and mine are unearthed, as per this guys 'how-to':

. I have been running this mod for about 2 years with great success. But only today noticed the jump to about 19VDC. My battery ran down quite low a number of times... does anybody know if this could be the cause? I've heard a faulty rec/reg can kill a battery, can the opposite occur also?

 

[pamcopete]

Thunzie,

The regulator is connected to the load side of the ignition switch, not directly to the battery, and as a result the regulator actually regulates the voltage on the load rather than the battery itself. The output from the alternator from the rectifier is connected directly to the battery, so you can have a situation where the alternator has to produce a higher voltage at the battery in order to satisfy the regulator that is on the other side of the main switch, the difference being the voltage drop across the contacts of the main switch.

So, measure the voltage on the load side of the main switch and also measure the voltage drop across the contacts of the main switch. You could have a main switch with a high voltage drop across the contacts.

 

[vr3506]

Thunzie,

The regulator is connected to the load side of the ignition switch, not directly to the battery, and as a result the regulator actually regulates the voltage on the load rather than the battery itself. The output from the alternator from the rectifier is connected directly to the battery, so you can have a situation where the alternator has to produce a higher voltage at the battery in order to satisfy the regulator that is on the other side of the main switch, the difference being the voltage drop across the contacts of the main switch.

So, measure the voltage on the load side of the main switch and also measure the voltage drop across the contacts of the main switch. You could have a main switch with a high voltage drop across the contacts.

And not to forget all the connectors.

I haven't heard about a battery destroing the rectifier/regulator. But when everything else is tested and ok, I would try with an other rect/reg unit first.

Maybe what I say next sounds stupid, but I once had a multimeter, wich showed far to high voltages when the battery was almost empty.

Btw Thamworth, nice area, we've been there twice, bud didn't see any XS-ses

 

[Thunzie]

Thunzie,

The regulator is connected to the load side of the ignition switch, not directly to the battery, and as a result the regulator actually regulates the voltage on the load rather than the battery itself. The output from the alternator from the rectifier is connected directly to the battery, so you can have a situation where the alternator has to produce a higher voltage at the battery in order to satisfy the regulator that is on the other side of the main switch, the difference being the voltage drop across the contacts of the main switch.

So, measure the voltage on the load side of the main switch and also measure the voltage drop across the contacts of the main switch. You could have a main switch with a high voltage drop across the contacts.

Thanks for your reply Pamcopete, but are you taking into consideration the modified electrics that I described or are you talking from the point of view of a standard XS?

 

[pamcopete]

Thunzie,

As far as I know, all motorcycles of this vintage are wired the same way. The output of the alternator, through the rectifier, is connected directly to the battery. The regulator is connected to the load, so the regulator sees a voltage on the load side of the main switch that is lower by the drop in voltage across the main switch.

I have 5 motorcycles. Three Hondas an XS650 and a XJ550. The four that have a conventional alternator are wired as I described. The fifth is a CB450 with a PMA and it has a shunt type regulator that also has its voltage sense wire connected to the load side. Thee of the four bikes with a conventional alternator like the XS650 and the XJ550 have a combined reg/rect. All that means is that the regulator and rectifier are in the same box, but they are still independent devices.

If you are using a reg/rect designed for a PMA, then that is not appropriate unless you have installed a PMA in your bike. The stock alternator on an XS650 is a excited field type of alternator and should be regulated by the appropriate regulator/rectifier.

If your setup is different than these examples, then please post a circuit diagram.