My batteries are fairly new and in good health. I have no charging issues or starting issues. Everything is in good health and my truck needs nothing; it's better than when it left the lot.
I've been following some of the alternator threads lately and doing some checking of my own and found this on the first cold start each day:

Battery volts - 12.4
Glow plugs on - 11.5-11.6
Engine cranking - 10.5-10.6 (just for a split second).
Cold idle (glow plugs on) - 12.0
Idle (glow plugs off) - 13.9-14.0

Am I in an acceptable range here? I mean as soon as the glow plugs turn off voltage shoots up to 14 at idle. I will get a bigger alternator if Im convinced it is necessary but I dont want to just for the hell of it to add another mod in a sig.

 

Those are good numbers, especially at the OBD port whereas at the batteries you'll likely see .2-.4 volts more.

Especially impressive if that's the stock 110 6G. Those numbers seem to reflect the 140 amp upgrade though.

Josh

 

I haven't checked to see which alternator is on there, but I will see if I can identify it.

 

Keith the Numbers look good, but you need to put a load on the alt= AC motor full on, Radio on, lights on, throw everything you have power on Engine warm , you should never see 13.3 full load or lower, after glo plugs it will be on the low side same with batts, I see 13.9 /14. alt batts run 13.5/14 full load it will Fluctuate from 13.7 at times mostly 13.9/14

 

this is with a 140 amp alt ,the 110 amp never stayed the same

 

Headlights and A/C on max I see 13.9-14.1 volts at port.

Josh

 

What amp you have Josh? is it a DC?

 

I have the 130 amp 3G, which puts out 170 amps max.

I have been considering the new 250 HD from DC Power. Not sure if you have the habit like me, but I do not like putting the truck in gear and driving until the glow plugs cycle off.

Which can be annoying if several short trips or errands are being made, always waiting to drive off. With a higher output alternator I wouldn't be concerned with it anymore, as the voltage would be near 14 or more no matter what.

Josh

 

Mine pushes 165 max 140amp that's weird, I useally wait until engine temp is around mid 80s that way Trans is flowing too , there is always something to do before I head out- get the kids out of the house, flake the cows and horses, by that time the truck is nice and toasty.

 

I'm talking like cold start... wait then drive. Stop at coffee... wait then drive. Go to work, lunch time start engine, wait then drive... finish lunch start engine wait then drive and so on and so on...

Even more of a pain if there are several stops in a row like post office, bills, bar, strip club etc


Josh

 

Well from what I can tell, it looks like it is probably the original 178,000 mile alternator. Anything is possible though.

So full load at warm idle I'm showing 13.5. High idle (1200 rpm) it bumps to 13.6 volts.

So keep it for a while longer or go for the 140 amp 6G?

 

That's getting close13.5 full load, you don't want to Jeopardize the FICM, for that matter the Battery's. If you can swing it I would get the 140 amp unless you have big radio ,winch etc.

 

my 110 amp lasted 176 thou and some change, but it started working my batts and eat a ficm

 

That is why I put the 270 on my truck. My drive to work is 5 miles and in the winter I start the truck, crank the heater on high and drive to the shop. Rinse and repeat after work. With the high output alternator is sure is nice having a full charged battery all the time.

 

140 amps is still pretty weak for a Super Duty. At idle you can expect about half that and that will just barely cover your needs.

I just bought this 250 amp Powermax alternator on ebay for $170:
http://www.ebay.com/itm/281226124330?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITI don't think that price can be beat! I will test the output and if I don't get at least 100 amps at idle and 250 amps over 1200 RPM it's going back and the seller will get bad feedback...but they have good feedback so far.

Edit: Looks like the price is $153 today. I paid $170 on Friday...