Is it normal for a alternator to use 5 or more amps of battery power at idol? I have a 90 amp alternator charging a 4D battery. The alternator is sucking around 5 amps of battery power at an idol. (500 rpm). I need to rev the engine to about 1000 rpm to excite the alternator, then run about 800 rpm just to get to 0 on the amp gauge. There is no other draw of power on the system. Pulley diameter is 2 1/2 in. (Alternator) 7 1/2 in. (Engine) Both battery and alternator are new.
2006-06-20 16:51:05 · 3 answers · asked by Someonya 2 in Cars & Transportation ➔ Boats & Boating
The engine is a 371 GMC diesel. It's in a commercial fishing boat used for salmon trolling. I am in the process of putting on a larger pulley on the engine since the alt pulley is as small as possible. Good ideas so far...thanks.
2006-06-21 16:51:15 · update #1
You will not find many alt that work well at 500 rpm.
It is nice that your engine runs so nice at that low of rpm. I would set my idle up to at least 700-750 rpm.
Is this a diesel or Outboard or ??
If you put a smaller pulley on alt it will turn faster.
Ask yourself - How much idling do I do and is it worth it.
Do not trust an amp gauge for accuracy at idle.
2006-06-21 05:29:19 · answer #1 · answered by captbryguy 5 · 0⤊ 0⤋
The electrical system will use current ie.ignition,gauges etc. What kind of engine ? 500 rpm sounds kinda low 650 -750 would be closer. most alternators require around 1200rpm to SELF excit . your field wire may be loose or broken.it exits the alt. when ignition is one. you may have an alt that wont charge below 800 rpm which shouldn't be much of a problen unles you idle a lot. A HEI ign can pull around 10 amps .
2006-06-20 17:24:44 · answer #2 · answered by Robert F 7 · 0⤊ 0⤋
an alternator shouldnt draw any ele. it generates it. if your alt. is good then your gage must be off.
2006-06-20 17:06:40 · answer #3 · answered by wannac 3 · 0⤊ 0⤋