Holiday Alternator Experiments….

haywoodphotomaccom · 12-25-2012, 09:26 PM

Trivial info from experiments today….had a few minutes in-between family activities...

I have been thinking about getting one of the high amp output alternators and decided to see what the one I have was doing. We put a meter between the alternator and battery banks and when I turned the engine on it hovered between 5-10 amps going into the battery. The batteries were close to being full so that made sense. Turned a few things in the van on and off and watched the amp output go up and down a little.

I wanted to know what the max it would put out would be at idle with a heavy load. Turned on the wife's hair dryer it was pulling about 140 amps and watched the output of the alternator go up to about 60amps with the engine idling. I tried a bunch of different variations and 60 seemed to be about the max.

Second guessing the upgrade now….

**daveb** · 12-25-2012, 10:32 PM

I really don't know what the difference is between the 6.0 and the V-10 but at least on my van the engine took up a lot of the charge going to the house battery. Now like I've posted, this was only when I was running the Starcool...it is a load hog. If you don't have a problem I myself would not replace the stock alternator. Of course there is the microwave. It is nice to not have my separator kicking on and of during its operation but how often do you really need that?

yvrr · 12-26-2012, 08:32 AM

We turn on our engine (V-10) whenever we use either the microwave or the hair drier and the engine seems to put out the same amps as either of these appliances use...in other words, the voltage of the house battery is the same before and after use of one of these appliances...

haywoodphotomaccom · 12-26-2012, 08:36 AM

I was surprised to see how well the stock system handled it. Doing some more experiments this am.....

carringb · 12-26-2012, 01:11 PM

My stock 130A alternator has served me well so far (343,000+ on the odo).

I kind of decided I don't need one, even though I make some pretty good use of 2000w inverter. We did learn we can't fully warm up our race car's motor using our electric coolant pre-heater (external with quick connects and its own pump) before the battery voltage would drop. But it turned out out we melted down an inverter internally anyways, so more alternator won't help me until the inverter is upgraded. And even then a 2nd aux battery would probably do the trick.

The only other time I wished it had more power is winching. Once I was moving jersey barriers at the track to make a course modification. Had to move each one about 30', all sitting on nice asphalt. About the 3rd one it the battery voltage would drop enough I would lose the ability to fast-idle, and at that point the winch solenoids also stopped engaging. I took about 10 minutes or recharge time to start winching again. Even with more alternator however, I think I'd just run into heat issues with the winch moving that much weight continuously. I've also since upgraded batteries so I strongly suspect my alternator will no longer limit me when winching.

The thing that really helped me decide not to upgrade is all of the high-amp alternators have a 1-year max warranty. If my 130A alt ever goes out, I can replace it with a Napa lifetime alternator for 1/3 the cost of a high-amp, and then I'll never have to worry about buying another.

haywoodphotomaccom · 12-26-2012, 01:16 PM

Good info. With the 2 4D batteries, solar and better than expected alternator output I think I will be good for now.

JoeH · 12-26-2012, 03:18 PM

Good info but I'm still convinced a higher-output alternator is the way to go on these rigs. On a diesel a 110A is the bare minimum and to think mine lasted 7 years is surprising considering the additional load placed on it by an SMB conversion. Add in Starcool AC, onboard air compressor, and a winch I'm still of the opinion that I would rather have an alternator that's not working very hard to keep up with the load versus one that is working all the time.

And with regards to warranty, lifetime is nice but they usually apply to rebuilds and I don't know about anyone else but I've never had one that didn't have to be replaced. I'd buy new, if possible, regardless of output. And the warranties on most of the high-output alternators I've been researching are two years and not one.

carringb · 12-26-2012, 05:42 PM

I have seen a lot of failures with the 110A alt that came stock on the diesels. But it seems pretty rare for the 130A to fail.

carringb · 12-26-2012, 07:31 PM

I should also mention that most of the diesel alternator failures I see are due to bad starting batts. You essentially have 2 heat sinks to put a full draw on the alt vs 1 on the gassers. So check them regularly. A rig that starts reliably may still have bad batteries, and they'll ruin a FICM in no time on the 6.0's. I can see how a higher amp ALT will get along better with dual starting batts.

rob_gendreau · 01-01-2013, 06:21 PM

Anyone ever get a second alternator crammed into their van?