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Tool Talk Discussion Forum

Re: 48v delco alternator?

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Bob M

06-03-2013 14:03:07

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Most automotive alternators will develop 60 - 90+ volts when open circuited - ie. not connected to a battery. (A battery acts as a stabilizing ballast to the alternator output).

Presuming you can locate a suitable regulator, a Delco probably CAN successfully charge a 48 volt system. Issue is whether the rectifier diodes will hold up working at this higher voltage (they probably will). More problematic is whether the field/stator windings' insulation can withstand the greater "I squared R" heating losses that will be developed.

I'd suggest starting with a 24 volt Delco (plenty of them on Ebay), apply a custom-built regulator to it and see what you get.


Not certain why many wind turbines use permanent magnet fields. I suspect it's for efficiency (no energy lost energizing field windings) and better low RPM performance. The downside is regulating a PM field alternator is more difficult/expensive.

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George Marsh

06-03-2013 14:23:40

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 Re: 48v delco alternator? in reply to Bob M, 06-03-2013 14:03:07  
The current won't be any larger than the alternator's max rating. The resistance of the stator is the same, therefore the I squared R won't be a problem.

My concern is can the armature handle it? If you have an alternator say rated at 100 amps, should you push it to 100% or use some current less than 100%?

Last, where can you get a 48 volt regulator? The alternator will be connected to 4 12v batteries in series.


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Bob M

06-03-2013 18:58:39

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 Re: 48v delco alternator? in reply to George Marsh, 06-03-2013 14:23:40  
George - You are indeed correct about I squared R heating of the stator not being an issue!

My concern rather is the rotating field winding. Depending on the alternator electrical characteristics, the field could draw as much a 4x design current for the alternator to deliver 48 volts. And this would mean 16 TIMES the heat developed in the winding. Whether or not it would be a problem is uncertain.

As for where to find a 48 volt regulator, suggest paying a visit to your neighborhood electronics nut. If he's any good it should be a relatively simple matter for him to cob up a 48 volt PWM field control regulator.

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