and when your batteries and ficm last, you can thank us.

the oem stuff is a POS. seriously. i won't charge your batteries
past 25% charged.

a 185 amp, with no special connected loads, will run fine on oem
wiring. you can get the heavier cable if you like, and on F series
it's an easy upgrade.

oem is 120, and the current flow from engine loads cold is a couple
hundred amps.

oem wiring will work fine.

 

Fulthrot, I like your note to Ford. First time I read it. Ain't it the truth.

 

When I ordered my truck in '06, there were 3 alt options: std 110A, High Output 140A or dual Alts.

My factory batteries lasted well into 6 years and only one was just starting to go the other was perfect. My bud with an '04 and dual alts had his factory bats last almost 8 years. There is no way a starting batt that only gets charged to 25% will last. No Way.

The standard alt was undersized for sure. But seriously, all the factory alts are all crap? We have batts in the camper and trailers (dump, horse, car) we charge too... So much for the 140 being too small. That is of course my personal experience with my personal truck.

I can understand those that started out with the standard alt might have a bit of a grudge... Just sayin'....

 

the amperage isn't the issue. the output voltage of the alternator
is the issue.

when the output voltage of the alternator is the same as the voltage
of the batteries, there is no difference of potential, and no current flow.

to fully charge a auto battery, you need to apply 14.5~14.8 volts DC.

and magically, that is the output of DC power alternators. OEM stuff
outputs at 13.2~13.3 volts DC.

if you charge a lead acid battery with a 13.2 volts DC power supply,
and then let it rest, it'll show a specific gravity of 25% charge.

ampacity doesn't even enter into the equation. ampacity is the load
the battery serves. how many amps of current the load draws.

if the power source can't deliver the amps of load hooked up, the
voltage falls off.

the DC power alternators maintain a 14.8 system voltage when
running. that means that the batteries are being charged, and
at the same time, the FICM and other loads are getting full voltage.

the ficm is sensitive to voltage, 'cause it's an amplifier. it takes
12 volts, and makes it into 48 volts to drive fuel injector coils.

the lower the input voltage, the MORE CURRENT the ficm draws
trying to put the specified 48 volt output.

CURRENT creates heat, not voltage. and heat is what causes your
ficm to get toasted.

i'm not bitching about OEM alternators 'cause i hate ford, or suffered
improper toilet training. i'm bitching about them, 'cause i'm an
electrical contractor, and understand enough about electrical power
to be a threat to others...

and 'cause i got a clamp on ammeter and started measuring current
flow when you start up cold in the morning.

the larger ampacity alternators are capable of running all connected
loads at 14.6~14.8 volts, even with a cold engine and glow plug loads.

the ONLY time my batteries are EVER discharged any more is cranking
the engine. about 10 seconds after the engine starts, the voltage goes
up to 14.8 volts, and the alternator is charging the battery while
supplying the glow plugs and anything else i have turned on, including
1,800 watts of amplifiers, which is about a 2.5 horsepower load.

so all this long winded diatribe is really to make the point that the
140 amp stock alternator won't run the glow plugs by itself. the
batteries are providing the shortfall, and being discharged in the
process. when the glow plug load falls off, the alternator then can
actually start charging the batteries.

if it has enough voltage to do so properly. the OEM unit doesn't.

 

Charging a lead acid battery at over 13.6 volts only lessens charge time at the expense of heat which will eventually boil the water out of the battery and kill it. Over 14.5 volts charging you are cooking the battery. If you can't get a full charge on the battery with 13.6 volt input you have a problem with the battery. A full charged 12 volt battery should show 12.6 volts, 2.1 volts per cell, charge rate is 2.3-2.4 volts per cell.

 

Guess I have to agree with jsm180. 12.6 to 12.7 volts at rest is a 100 % charged wet cell battery. Our hydro generator stand by station wet cell batterys are on a constant float voltage of 13.5 to 13.6 volts. Any constant higher than that can boil the batterys.

 

Hmm, I hadn't ever considered charge voltage. I've got two AGMs that I don't want to kill. Anyone have more info on pros/cons of 14.8v vs. 13.6v charge voltage? I can see both sides, but I wouldn't mind some more info.

 

A low charging voltage is going to take a lot longer to completely charge the battery. These are not in a trickle charge standby situation.

 

AGMs and Flooded cells can be charged similarly -- it's the Gel Cell batteries that are easily killed with too much charge voltage.

With all the folks running DC alts, you'd think there would be complaints of folks toasting batteries -- but I haven't noticed any such threads...

My volts I'm reading on Torque range 13.4-13.6V I've seen lower right at start and as high as 13.8V.

 

From my experience those are normal readings. However I will also say that the Autozone alt. in my 428 cj will quite often exceed 14 volts. The key here may be in having a quality voltage regulator in the alternator.

 

You probably won't see a problem unless you run long trips, an hour or so won't get the battery hot unless you are up around 15v.

To answer the op's question, you need to match the alternator to the system load. 140 amps on a stock truck with std electronics and lights is plenty of power.

 

fyi - Standard alternator capacity on the 6.0's is 110A - at least in many of the model years.

 

Not necessarily. Have you put an amp clamp on the system to see what the current draw is?

 

I don't think well ever all agree on the same thing here. Some will say adequate would be about to run the vehicle at 100% with no battery discharge, others will say as long as the battery doesn't die it's good enough.


I've done a little reading, sounds like 14.8v is good only if you have a good voltage regulator. For quick trips it wouldn't matter so much because the battery would always be charging. It would also be good for winter up here. But I do make several long trips a year and that is where it would start to boil the batteries. 3.5-4 hours is often, 6-8 hour trips are several times a year and possibly a couple longer. If the regulator dials down the voltage it will be fine. Like was brought up, there are lots of these floating around the forums and I haven't heard of people complaining of boiling the batteries. But I'd still like to see more info.

 

all i've got is my experience, and what i've observed with meters.

and what i've found on the net..... this is the charge profile for
oddesy batteries, an AGM battery. this is how the oddesy chargers
do the deal. i have a 50 amp single bank one, and i've measured
it during it's charge cycle, and it does what the graph says.
it's a $300 charger. it works.



now, with the brand new van, and oem alternator, the oem batteries
lasted 18 months. i replaced them with a pair of oddesy batteries,
and those lasted 18 months with the oem alternator, and the
thing always cranked over weakly. sometimes i'd put a charger on it,
just to top off the batteries.

here's my observation on batteries, both industrial battery room
lead acid batteries, ganged in series for 120 volt dc, each battery
weighing 275 lbs, and having two volts, and auto batteries.

you are transferring energy from one place to another. there has
to be a delta to cause current flow. if you charge a battery with
a 12.5 volt source, it will never reach 12.5 volts static charge.

and when i was charging my batteries at 13.2 volts with oem
alternators, the resting voltage never exceeded 11.6 volts on
the batteries.

my batteries, measured right now with a fluke DMM are 12.55.
when i start up the van, the system voltage goes up after about
15 seconds to 14.6~14.8.

check how many people on this forum are running DC power
alternators.

now, how many are posting how their batteries are toasted?