Cant overcharge as ling as the regulator is good.
No stock alternator will put out 90 amps at idle, get a voltmeter and read it. 40 to 50 if your lucky. Max output will vary by manufacturer by as much as 20 amps and 1,000 rpm.
If you have a camper with dual deep cycle batteries plus the 2 in the truck, plus lights, AC, Radio, fans and a couple cell phone chargers, you will be overtaxing a 145 amp alternator. You would be ok with duals.
I have a coolant filter mounted where the 2nd alternator would be, so I had to go bigger single. Mean Green is american made, stand by it and worth every cent. Like I said, mine is 6 years old and strong as the day I put it in.
Can you get cheaper? Yep. Can you get a better alternator? Nope.
6 years and 2 trucks later, still got mine and before that I had 2 in 2 years at $200 a pop. Mean Green was my choice for a reason. I had 5 batteries hooked up and a 2,000 watt stereo with dual dvds.
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