alternator at risk? 28 amp ST1100

[DeanR]

Just installed my extra lights (Electrical Connections 55w) from my currently disabled 99 onto my 91. Only other thing plugged in are my Symtec grip heaters which I do use a fair amount. The 91 shows no signs of any alternator troubles at present. All connectors look great. In my paranoia, I added the Honda marine voltmeter. Will the use of these lights promote future issues? And if so, why? Is it simply making the alternator somehow work harder, with a resulting shorter life? Needless to say, I don't exactly follow how all the elec. stuff works.

ps. 60/55 headlight
Stebel horn which I assume has no effect, as it is used once or twice a year.

 

[Mark]

Michael Martin's ST1100 site on 28 amp loading might be of help to you...

LINKY

 

[DeanR]

The extra lights are now connected. While underway, the voltmeter reads about 12.4 with them on, about 14.2 off. Should I use em or would it be a bad idea?

 

[wjbertrand]

That's quite a drain. The max voltage on the 28A doesn't happen until you're turning about 5K RPM, so most of the time when underway you will be below max voltage output. With the battery fully charged and allowed to sit over night, what does the voltage read? If it's higher than your underway reading you are discharging your battery. I don't think the stator will live long under such conditions.

 

[Norm]

It might be useful to install an oscilloscope on several of the 28 amp VRR units as I am not aware of whether they shunt the stator legs, shunt the output to ground, or block/interrupt output in order to control output. 28 amp alternators which I have measured vary between 28 and 32 amps output although some may have been higher. Too lazy to check my notes.... I remain unconvinced that load is the cause of failure of these stators.

Jeff is correct regarding the loading of your system as regards its ability to carry the load applied. If the voltage is not above the min-13's, no charging of useful degree is possible despite that it may power lights.

One opportunity for reducing load is to replace the headlights with HID as these draw only 2.1 to 2.2 amps when operating as opposed to over 3.5 for even the 45 watt bulbs. While a 42 amp (typically closer to 60 amps) alternator does not care about a few amps. the opportunity is there for the 28.

If still running a 28 amp unit, I would be tempted to use an automotive regulator such as a Delco 2SI mounted separately in order to reduce heat in the combined unit. These are cheap off EBay.