alternator question
If an alternator is rated 200 amps,why cant they tell you at what RPM this rating is good.At idle,650rpm, or at cruising,1950 RPM. If you get a diesel rig,there is a high idle setting to get more amp...
Forum Discussion
As an example of an alternator output curve, here in this .pdf on page 6 of 7 are output curves for the 130 amp alternator in our 2005 E450 Ford V10 motorhome.
These curves show alternator output in amps versus temperature versus alternator RPM. Note in the chart just above the curves that our V10 engine alternator is OVERDRIVEN above engine RPM by a ratio of 2.72 to 1. This means that when the engine is idling at around, say, only 600 RPM - the alternator is actually spinning much faster than this. To determine approximate maximum alternator output at any given engine RPM, multiply engine RPM by 2.72, then use this RPM on the chart to see what amperage the alternator is capable of putting out at that engine RPM:
https://www.fleet.ford.com/truckBBAS/non-html/2005/vs_pdf/05elect.pdf
For our case I estimate off the curves that when the V10 is idling, the alternator is capable of providing 60 - 70 amps in combination to the chassis electrical system and the motorhome's batteries. I have seen the alternator providing up to 50 amps into partically depleted coach batteries while the engine is idling. (I have an ammeter permanently mounted on the cab's dash that monitors current into and out of the coach batteries.)
These curves show alternator output in amps versus temperature versus alternator RPM. Note in the chart just above the curves that our V10 engine alternator is OVERDRIVEN above engine RPM by a ratio of 2.72 to 1. This means that when the engine is idling at around, say, only 600 RPM - the alternator is actually spinning much faster than this. To determine approximate maximum alternator output at any given engine RPM, multiply engine RPM by 2.72, then use this RPM on the chart to see what amperage the alternator is capable of putting out at that engine RPM:
https://www.fleet.ford.com/truckBBAS/non-html/2005/vs_pdf/05elect.pdf
For our case I estimate off the curves that when the V10 is idling, the alternator is capable of providing 60 - 70 amps in combination to the chassis electrical system and the motorhome's batteries. I have seen the alternator providing up to 50 amps into partically depleted coach batteries while the engine is idling. (I have an ammeter permanently mounted on the cab's dash that monitors current into and out of the coach batteries.)
