High output alternator experience

JoeH · 12-07-2012, 04:37 PM

I think my alternator is dying. The battery light on the dash comes on at any voltage output below about 12.5 - 12.7 volts. It will drop as low as 11.2 but then bump back up into the 13s. I know this from watching VLT on the Scanguage. However, with a cheapy voltmeter in the cigarette plug the voltage doesn’t fluctuate as much. I presume because the dual starting batteries absorb some of the fluctuation and stabilize the voltage.

They are pricey but a high-output alternator makes sense given the accessory loads on the typical SMB versus the stock 110A alternator. Especially given the need to fully charge the house battery. I read somewhere while researching threads that SMB recommends solar panels and/or connecting to shore power to fully charge the house battery(s), as the alternator will only charge the house battery(s) to about 90% capacity. I plan to add solar one of these days but in the meantime any input from those who have added a higher output alternator is appreciated. I’m looking at this 250A model which puts out 180A at idle. https://www.dcpowerinc.com/fit/2005~For ... 50-xp.html

Any input versus stock appreciated. And if you did install a higher output model did you have to upgrade all the grounds on the engine or any other changes to the factory wiring harness? Or can you get by with just running an additional wire(s) from the alternator to the battery to carry the extra current? Thanks, Joe

charlie56 · 12-07-2012, 08:57 PM

You sure its not your starting batteries? Have you ever replaced them in your 2005 SMB? If not, I would certainly look there first. Everything goes haywire if they go bad. I have a 2008 and mine just crapped out. $280 at Interstate Battery and 8 hours of my install time (what a pain) later, everything is back to normal.

**daveb** · 12-07-2012, 09:41 PM

The way I could tell I had a bad battery was to look what the shore power charger is putting out in amperage. If the charge doesn't taper off, you have a short, usually in one of the batteries.

I did replace my alternator due to the slightly larger load the Starcool pulls. I think I'm running a #8 copper wire to the batteries but could be wrong. I did replace the lug at the alternator. I figured what had been installed was good enough, because I didn't really add any more load than what I had. Yep, I'd like to have a #6 or even a 4 strand copper bus to the batteries but so far so good. The voltage drop was a concern but ended up no big deal. The amperage hasen't changed that much and with 270W of solar I think it's good. The twin 4-D's never get too low and don't seem to overload the bus. The microwave is the monster, but no problems to date and I use it often with the engine running.

I purchased a 240 or 270a alternator (can't recall) from Nations. A few issues getting the case to to fit in my 6.0 (a bit of grinding on the case) but this one is by far the best I've used to date. Give Adam Nation a call and ask about Dave Boyer's heavy duty alternator. I'm satisfied with it.

JoeH · 12-07-2012, 11:26 PM

hey, thanks for the replies. I replaced the starting batteries a little over a year ago with two Interstate Megatron Plus batteries (850 cold cranking amp ea.). It could be that they are going bad but that would indicate I have a short somewhere. My 4D house battery is 5 years old but still seems to be holding up. I'll have them both load tested.

I also have the Starcool and that's another reason for wanting a bit more alternator juice. I'll pick up a multimeter so I can check what the shore power charger is putting out in amperage.

**daveb** · 12-08-2012, 11:12 AM

I was lucky to get more than 2 years out of flooded starting batteries so I went AGM and no more problems. I think the solar had something to do with killing the life of the starting batteries but it also gets kinda hot in the summer around here.

JoeH · 12-08-2012, 02:25 PM

Kinda odd. After two days at rest and off shore power both starting and house batteries read 12.9. There is a drawdown in the 11.2-11.5V range as the glow plugs do their thing. After 120 sec or so voltage comes back up and fluctuates between 12.5 and 13.4 at the Scanguage and holds more steady at 13.9-14.1V at the cig plug-in voltmeter. I drove it around town for an hour looking for the best price on diesel and it never dropped below 12.5 and there was no battery indicator light flicker on the dash. Back to normal by all appearances.

The only other odd coincidence the day this all started was I had my oil and fuel filters changed at the dealership. I don't think they disconnect the battery to do this or have to disconnect anything near the alternator to get at the more difficult of the two fuel filtest. But maybe?

Otherwise, if the lower voltage comes back I'm starting to think bad diode. I think it is eventually going to crap out. That, or deep down I really want a DCpower alternator. Still cheaper than Deaver Springs

**daveb** · 12-08-2012, 03:37 PM

Quote:

Originally Posted by JoeH

Kinda odd. After two days at rest and off shore power both starting and house batteries read 12.9. There is a drawdown in the 11.2-11.5V range as the glow plugs do their thing. After 120 sec or so voltage comes back up and fluctuates between 12.5 and 13.4 at the Scanguage and holds more steady at 13.9-14.1V at the cig plug-in voltmeter. I drove it around town for an hour looking for the best price on diesel and it never dropped below 12.5 and there was no battery indicator light flicker on the dash. Back to normal by all appearances.

The only other odd coincidence the day this all started was I had my oil and fuel filters changed at the dealership. I don't think they disconnect the battery to do this or have to disconnect anything near the alternator to get at the more difficult of the two fuel filtest. But maybe?

Otherwise, if the lower voltage comes back I'm starting to think bad diode. I think it is eventually going to crap out. That, or deep down I really want a DCpower alternator. Still cheaper than Deaver Springs

That's normal on the glow plug voltage, mine drops lower than that. It also take a while for the exciter to ramp up the alternator voltage to a normal 13.3 to about 14.2 depending on the alternator. I've never seen a motorcraft alternator put out less than 14 volts though.

I don't know why you're getting a difference of that much between the lighter socket and the Scangauge. Have you un-plugged and re-plugged in the Scangauge (RS-232type port)? Those are finiky and often can corrode.

To replace the filter they usually pull a wire loom loose...maybe they didn't get a ground on or shot a screw through it...sorry not sure what that set of wires run, but somebody here should know.

I'd check voltage at the fuse block under the hood and compare it to your other spots.
Still, dropping to 12.5 volts usually indicates the alterator's regulator going out. I was running a 200 amp model that had a voltage range of 12.8-13.8 and ran normally around 13.4
Guys in our shop always check voltage and connections at the starting battery as well.

Good luck Joe

JoeH · 12-10-2012, 01:25 PM

Thanks for the help DaveB. Still running normal but one little flicker on the dash has my antennae up and bad dreams of being stranded somewhere. Everything on the 6.0 needs lots of constant 12.8+ volts. The ficm puts out 48volts. Charging and healthy batteries are crucial so I get nervous.

I've been reading the diesel forums and with regard to testing voltage from the cig lighter (mine is sometimes lower than 12.5 at idle but cruising it's back up to 14.1 or so) the OEM charging system was designed to output ~13.0 volts at idle (it’s a result of low engine rpm). At higher rpm the alternator is within its peak charging window. With voltage drop thru a variety of relays and small OEM wiring, 12 volts is considered normal but not ideal.

When the time comes and I think it's sooner than later I'm going with a high-ouput alternator irregardless. In researching the 6G large case options it sounds like just amping up an OEM configuration wont last which is why I'm looking at the DCpower option. A complete redesign.

**daveb** · 12-10-2012, 03:16 PM

Well I finally found the stats on mine and it's a Nations TAD-275XP. (275A)
They have upgraded those to a 300-SPX which is built even a bit tougher. Used on emergency
equipment and military applications, they idle at 200amps and are designed for high heat.
They have a 12 diode rectifier system and are supposed to be a direct drop in fit.
Cost = $519.00

Good luck on what you end up with Joe.
The 275 I installed did need a slight mod to fit
flush with one of the brackets that Ford
took off when they put one of the
stock units in before I upgraded

BTW, makes sure you get the right nose pully and that it's torqued correctly.

JoeH · 12-10-2012, 05:12 PM

Quote:

Originally Posted by daveb

Well I finally found the stats on mine and it's a Nations TAD-275XP. (275A)
They have upgraded those to a 300-SPX which is built even a bit tougher. Used on emergency
equipment and military applications, they idle at 200amps and are designed for high heat.
They have a 12 diode rectifier system and are supposed to be a direct drop in fit.
Cost = $519.00

Good luck on what you end up with Joe.
The 275 I installed did need a slight mod to fit
flush with one of the brackets that Ford
took off when they put one of the
stock units in before I upgraded

BTW, makes sure you get the right nose pully and that it's torqued correctly.

Thanks for the info. Makes sense to replace the serpentine belt at the same time? I believe the SPX sold by Nations is made by DCpower which is the manufacturer of the XP alternator I'm researching. The major difference being the rectifier is laser welded, it has a hairpin design stator and better technology. Here are two pages that explain the alternators technologies (hit the Read More Button)

https://www.dcpowerinc.com/high-output- ... ators.html
https://www.dcpowerinc.com/high-output- ... ators.html