From: John De Armond
Subject: The Power Quest Continues
Date: Sat, 15 Jan 2000 03:28:41 EST
A few weeks ago I posted about my quest to equip my Itasca Class C
motorhome with enough engine alternator and inverter to run all
normal 120 volt loads except the air conditioner without having to
run the generator. Specifically, the microwave and coffee maker.
My desire is to be able to achieve continuous operation with the
engine running while not dipping into the house batteries. I intend
to have two alternators on the engine - one for the engine and
cranking battery and a totally separate system for the house
batteries and the inverter. A standard cross-connect relay will
remain installed so that the systems can be cross-coupled if one
My last post had to do with making the decision between 12 volt and
24 volt systems. I wanted the 24 volt version but alas, there
simply isn't enough room for a 24 volt alternator in the engine
bay. Indeed, space is going to be the single biggest problem.
To run a 1500+ watt inverter, I need about 200 amps of generating
capacity. A quick search of the net pops up products from places
like Ample Power but at very steep prices, sometimes approaching
$1000. Too rich for my blood. Besides, the engineer in me said "do
it yourself". Another potential source was the vendors of high
output alternators sold to the kids who like to make their cars go
BOOM BOOM with big stereos. Alas, an examination of several of
these alternators revealed that they are little more than slightly
reworked regular alternators. In other words, low duty cycle and/or
short life at the higher output. It appears that they spent more
time on the chrome plating than they did on re-engineering the
I talked to a local ambulance company owner and inquired as to who
equipped their ambulances with high capacity alternators. He
pointed me to Red Hot Battery Service here in Cleveland. Dudley,
the owner, builds the special, high capacity alternators. He uses
the large frame semi truck alternators and rebuilds them to make
200+ amps as a 1 wire unit (self-exciting). The price was great
too, at $265.
Brought a bad unit home to check for clearances. Damn! Itasca
built the body of the MH so tightly around the engine that I would
have to cut away and rebuild part of the bracketry that supports the
body on the frame. Doable, but very time consuming. Back to Red
Hot. We decided to take a look at late model large car and SUV
alternators. The alternators have grown with the increasing power
demand in late model cars. Our eyes settled on a Delco alternator
for a late model Cadillac. This alternator is rated for 145 amps.
Dudley told me that he was sure that when converted for one wire
operation, it should be capable of near 200 amps. The best part is
the price for a new (not rebuilt) unit is going to be under $150.
Normally this alternator comes with a serpentine belt pulley.
Dudley knows how to convert it to a V-belt drive which I must have.
The nice thing about this alternator is that if one isn't enough, it
is small enough that another can be mounted alongside it.
OK, so the alternator is on order and will be here middle of the
week. I have a bad core unit to use to begin fabricating the
mounting brackets. I'll keep the list informed on how this goes.
Assuming everything works OK, I'll post part numbers and Dudley's
phone number. It looks like I can get the power generation side of
this system done for under $200.
I'll initially use the internal diode bridge in the alternator but I
intend to fit the alternator with larger external diodes later.
I've had great success in doing this in the past. This gets the
diode heat away from the alternator, the engine heat away from the
diodes and lets me use rugged high voltage stud rectifiers instead
of the crappy little chip rectifiers the OEMs use. More on that
The specialty deep discharge battery charging voltage regulators
such as the ones made by Ample Power (http://www.amplepower.com/)
and Cruising Equipment (http://www.cruisingequip.com/ - note: these
pricks charge for tech support!) are computer-controlled and will
very rapidly recharge large house batteries. They implement the 3
stage charging cycle and monitor battery temperature to prevent
overcharging. They are also quite expensive. They are primarily
aimed at the offshore marine market where it is desirable to
recharge the house battery with only a short engine run time each
day. I'm going to initially use a simple internal regulator. The
regulator that Dudley uses can be strapped to one of several
voltages to match the application. Then I'm going to study the
build-or-buy decision on the smart regulator. I kinda have the
urge to do another embedded microprocessor project so I have a hunch
I'll be building my regulator, particularly since I want to do some
things that neither of these commercial ones do.
I'm going to order the Statpower ProSine pure sine wave inverter,
probably the 1800 watt unit. I've had very good luck with this
brand in the past and I just can't justify the price difference
between the Statpower and the Heart and other high priced units,
especially since I won't need high power shore power battery
charging. I'm going the sine wave route because I'm tired of trying
to suppers the hash that pseudo-sine inverters generate. Really
screws up AM and ham radio. The pure sine inverter is a bit less
efficient but since my main use is to run it from the alternator,
that doesn't matter much.
I'll keep the group apprised of what is happening. This is going to
be fun! And it gives me the excuse I needed to order a new MIG
welder (the Miller 250X kicks butt!) yesterday. :-) I'll probably
end up with a writeup and some pictures on the web site when I'm
From: John De Armond
Subject: Re: The Power Quest Continues
Date: Mon, 17 Jan 2000 20:01:43 EST
Dick Lucas wrote:
> Neon John wrote in message <38803011.49AE74BE@bellsouth.net>...
> >the price for a new (not rebuilt) unit is going to be under $150.
> >Normally this alternator comes with a serpentine belt pulley.
> >Dudley knows how to convert it to a V-belt drive which I must have.
> Be careful with your conversion from serpentine to v-belt. My '83
> southwind, with a 65amp alternator regularly went through the v-belts. I
> have seen a number of posts about the same problem with that setup (454
> Chevy) and came to the conclusion that a single v-belt simply couldn't
> handle that much power reliably. 65 amps is around 1.25 HP, a 200 amp
> alternator would require about 4HP, which is a lot for a single v-belt.
> Also on that belt was the water pump and the air pump, but they don't
> consume much power. Sometime around 87 or so, the 454 switched to a
> serpentine belt. I suspect that it was just because of the belt problems.
> To reliably transmit that much power may require a dual v-belt setup.
> I got pretty good at changing the belt on the side of the road, and always
> carried at least 2 spares for the alternator belt.
yeah, me too. My 68 Fury's appetite for belts runs about 2 a
summer. :-( One of the little things one learns to put up with to
enjoy old cars, at least until the engine transplant :-) I've been
eyeing a serpentine belt conversion for my MH. I'm not sure if I
want to do that much work or not. I think I can mount the new
alternator so I can get a dual belt drive on it. If not, wellll,
then I'm pretty good at changing belts.
From: John De Armond
Subject: Re: Inverter battery capacity adequate?
Date: Tue, 21 Mar 2000 18:19:52 EST
Randy Howe wrote:
> Cool idea John. How did you mount the second alternator? Do you have a main switch on
> it so that there is no electrical load and consequently no mechanical load on it when
> not in use?
Welded up a bracket to mount where the old, long abandoned AIR pump
was. Extended the waterpump belt to fit.
I went one-wire because the alternator shop guy recommended it.
I'd probably not do that next time so I could turn the alternator
off whenever I needed to by switching only the excitation. Now I
have the second alternator hooked directly to the house batteries.
I still have the cross-over relay so that I can parallel the
batteries if either alternator fails. I'll probably put another
relay or manual disconnect in the second alternator lead at some
time in the future. The nature of the one-wire regulator is that it
does not excite the alternator until 12 volts is applied to the
output terminal so switching it off is as easy as disconnecting the
To tell the truth, if I had it to do over again on my particular
rig, I'd just put the Cadillac alternator in place of the stock 80
amp unit and be done with it. It was a LOT of work to fit the
thing in this tight engine compartment. The chassis load is pretty
low unless the headlights are on so I would have lost only a little
capacity by running the chassis on this alternator too.
Tip for fitting a different length belt to a modified drive system
without a lot of guessing. Get a belt longer than what will be
needed. Cut the belt. Pull it around the pulleys. Overlap the
ends. Mark one end where it overlaps the other. Take this belt to
the auto parts store and ask them to measure the belt on their belt
measuring tool while holding the marks in alignment. This technique
saves a LOT of headaches in getting just the right length belt, as
you don't have to worry about groove depth compensation and such.
From: John De Armond
Subject: Re: Inverter with Air Conditioner
Date: Sat, 19 Aug 2000 21:16:44 -0400
> Has anyone been able to run one A/C underway with an Inverter, if so what
> size - 2000 2500 3000watt?
> The A/C I will be using is a Brisk Air Heat Pump 15,000 btu with 15.4 draw.
> It is the surge current I'm concerned about. Heart and Trace Inverters are
> rated about 2x for surge yet I have heard A./Cs have a surge current of 3x.
> Please don't misunderstand, I want to run 1 rooftop A/C in extreme hot
> conditions while traveling to suppliment the dash A/C rather than run the
Don't you just love it when you ask a question and you get
everything BUT an answer? So goes Usenet.
I have run a 13kbtu AC on a 2500 watt inverter and it didn't seem to
strain the inverter at all. I think that the definitive answer
would come from Heart (or whichever brand you choose.) since I'm
sure this is a common question.
On the subject of alternators, no need for a "huge oil cooled unit"
to supply the current. Here: http://www.vitalalternator.com/ is the
place to get the so-called "ambulance alternators". These are
designed for emergency vehicles that require hundreds of amps of
CONTINUOUS 12 volt power with the engine idling. It's gonna be
expensive - don't plan on getting anything back from a K note - but
hey, it's a Newmar, right? :-) I've never done business with these
guys but my friends at the local FD have, which is where I got the
If you choose to use an inverter but DON'T go this route with the
alternator, you might want to make sure that the existing alternator
is rated for continuous full output. Most aren't. With the
inverter on, the alternator will be pegged out and the battery bank
will supply the rest. You might also want to make sure that the
belting is rated for continuous full output. Experience tells me
that a single belt won't do it - tandem belts are required.
From: John De Armond
Subject: About Alternators
Date: Thu, 14 Aug 2003 23:10:57 -0400
As the result of writing a couple of short articles on the subject and the
google archives I get a LOT of questions from people who want to upgrade
alternators on their vehicles. Most have read the cruft in the car mags about
one wire alternators and think they're the berries. They're not.
Today I find this web site where the dude explains why one wire alternators
are so bad. In the process he does a very good job of explaining charging
systems in general. Read these URLs in sequence:
This one addresses another pet peeve of mine, shitty headlight wiring
I've yet to find a modern car with adequate headlight wiring. That includes
my Caprice cop special with super-heavy-duty everything. If you think your
night vision is going away it might just be your headlights.
I do one thing different from this article when converting headlights. I take
the power directly off the alternator output stud. The benefit is up to an
additional volt or two for the headlights. This makes them much brighter,
makes them dim when the engine idles down and makes them burn out faster. I
decided that the tradeoff between maximum light output and shorter bulb life
is worth it, as my night vision really is on the decline.
One other upgrade to his plan is to use magnetic circuit breakers instead of
thermal breakers. The thermal breaker has to drop a little voltage in order
to generate the heat it needs to operate. The magnetic breaker drops almost
no voltage. I use purpose-made breakers when I can find 'em. Ordinary
household breaker box breakers work well too. They have a thermal element but
it is of such a low ohmic value as to be of no consequence.
All in all these are the best writeups I've seen on the topics.
From: John De Armond
Subject: Re: Alternator problem
Date: Fri, 27 Aug 2004 01:37:39 -0400
On 27 Aug 2004 03:43:41 GMT, email@example.com (Yaabob) wrote:
>I went from a stock 42amp alternator on my class A to a one wire 135 amp. After
>all was done I started up. The alternator began producing 13.5 volts and I
>increased the RPM. It went up as high as 14volts and started dropping down.
>Then it stopped putting out all together. The motor ran on the battery and
>dropped its voltage down to 11.9
>I did upgrade the wire from the alternator to the battery with a cable as big
>as a battery jump cable to handle the larger output.
>I am at a loss why the alternator stopped producing. It is a new alternator for
>a 454 GM engine. Any suggestions of what may be stopping the output other then
>the alternator went bad. I suppose that could happen but a brand new one would
>be hard to believe. \
>Any help would be great.
Most likely smoked the diode bridge. I'm going to bet that the alternator you
bought is in the same frame as your stock one. It's been "upgraded", probably
with a few less but heavier turns in the stator. This will let the alternator
flash 135 amps (probably. Some of these are simply frauds) which impressed
the boom boom stereo kiddies but the alternator cannot produce that kind of
current continuously. You inadvertently made the situation worse with the
very heavy lead wire.
To give you an idea of what I'm talking about, consider the following photo:
This photo shows a continuous duty Leese Neville 100 amp alternator as used on
semi trucks next to a 90 amp rated compact car alternator. The Leese
alternator will crank out 100 amps until the cows come home. That little
alternator, which I have subsequently used on a small Cordless Battery
Charger, will flash 90 amps for a few seconds but quickly drops to around 50
as everything warms up. I hold the current to 50 amp in my application and
the alternator is happy.
You also saw another effect, one that makes a one-wire alternator
inappropriate for any application other than a race car where there are no
accessories. That is, the high voltage output. Since the one wire alternator
must, by definition, regulate its voltage at the output terminal, the
regulator must be set high enough to guarantee sufficient voltage to charge
the battery and run the accessories at the other end of who-know-what kind of
hookup wire. The one-wire alternators I've had an opportunity to test have
had the terminal voltage set in the range of 14.1 to 14.5 volts. With a heavy
duty connection with little voltage drop like you made, this high a voltage is
bad on both the battery and the lamps. Plus the partially discharged battery
drew enough current at this voltage to damage the alternator.
A conventional alternator regulates the voltage at the point where it gets its
excitation voltage, usually either the back of the ignition switch on older
vehicles or the main 12 volt relay on newer ones. The regulator drives the
field to generate whatever output terminal voltage is necessary to maintain
the sense point at the setpoint, usually somewhere in the range of 13.8-14
volts, depending on the ambient temperature. This maintains a constant
voltage on the electrical system which is good for the battery and great for
lamp performance and life.
Since a conventional regulator only requires one more wire, a source of 12
volts from electrically central point of the system, there is no reason to go
with the 1 wire option. I discourage the use of 1 wire systems even on race
cars, as the high voltage can make ignition and engine management systems act
up. Further, in my experience, the one wire regulators are not nearly as
reliable as the OEM parts.
What I suggest doing is finding a good automotive electrical shop, one where
the guy really knows alternators. Have him recommend a larger frame
alternator that will fit on your mounts. This will probably be an "ambulance
alternator". This is what I do. Our local auto electrician has been doing
this since the earth was hot and know most interchanges without having to look
at a book. If all else fails you can call mine, Red Hot Battery Sales in
From: John De Armond
Subject: Re: Motorhome alternator question
Date: Fri, 19 Nov 2004 18:56:09 -0500
On Fri, 19 Nov 2004 04:33:32 GMT, Sandy A. Nicolaysen
>Mike: I don't know why charging your house batteries would fry your
>alternator. It just doesn't make sense.
Yes it does. Conventional alternators are not designed to output their
rated current for very long. Both the general cooling in general and the
diode cooling in particular are inadequate.
>You can put a dead short across an alternator and it won't self
>destruct because the field collapses and the alternator outputs
That's irrelevant. The maximum heat is generated when the alternator is
at full output - current and voltage.
>Heat also reduces the output of an alternator because as temperature
>rises, the resistance of the stator also rises, reducing the output.
>A 100 amp alternator at 25C typically drops to 50 amps at 100C.
>My guess, and this is just a guess, is that a heavily loaded
>alternator gets hot and burns out the diodes. This was more of a
>worry back in the 60's than now. If your alternator has an internal
>regulator, that may be a factor too. Silicon hates heat.
>FWIW, my truck has two Leece Neville alternators from the factory. In
>8 years, I have replaced the alternator for the starting battery. The
>alternator for the house batteries is still intact, and I do a lot of
>boondocking with a block of golf cart batteries as a power source.
The Leece Neville alternator is designed for continuous output. Major
difference. Here is a photo that graphically illustrates the difference:
Both are nominally rated at 100 amps. The little alternator will output
100 amps for a minute or two. By the time the temperature equilibrates,
the output is down to about 50 amps and the alternator is HOT. The
Leese-Neville, OTOH, outputs 100 amps all day long and barely gets warm.
>If you are still giddy about the alternator, install a self resetting
>circuit breaker like the ones used for power windows.
That won't do a bit of good. You can't size a circuit breaker that will
protect the alternator from heat while also withstanding the peak output.
there are several things one can do. One, mount a remote thermometer on
the diode bridge and shut down the charging when the temperature gets too
Two, remove the regulator and diodes from the alternator. Mount the reg
in a more benign location. Replace the diodes with stud-mounted ones on a
larger heat sink mounted in the air stream. This will enable a
conventional alternator to generate almost its rated current indefinitely.
The increase in the resistance of the copper windings with temperature
becomes the limiting factor. This is a proven technique that works well.
>think Monaco is full of baloney.
Someone at Monaco might be full of baloney but in this matter they are
From: John De Armond
Subject: Re: Motorhome alternator question
Date: Sun, 21 Nov 2004 22:11:56 -0500
On 21 Nov 2004 12:52:29 -0800, firstname.lastname@example.org (dave martin) wrote:
>I did not intend to imply that Neon John's reply is incorrect. He is
>right on the mark. If you try to take full rated output from a normal
>automotive alternator for any length of time you'll fry it.
>I meant to point out that in most practical battery charging
>circumstances you probably won't be drawing to much current; at least
>that's what my measurements on common Delco-Remy internal regulator
Thanks Dave. I agree with your second paragraph. But. There are
situations where that can happen even with a TT/5th and truck setup and
the attendant high resistance path to the RV battery.
An example, I had a mid 90s T-bird in my shop a few years ago where the
owner was complaining about a weak battery that would not stay charged.
Of course, AutoZombie told him it was the battery and sold him a new one.
I did some measuring, looking at the alternator output current, the
battery current and direction and various voltages. What I found was a
basic design oversight. This guy had optioned the car to the hilt.
Heated seats. Thin film defroster, etc. With everything turned on
including the headlights, the 120 amp alternator was outputting about 110
amps (very good, considering how hot it was.)* About 10 amps was flowing
OUT of the battery. IOW, the car load was about 10 amps more than the
alternator could output. The system voltage was down to about 12.6 volts
and was steadily dropping.
Someone at Ford had simply screwed up when they set up the option and
power draw matrix. He could not get Ford to acknowledge the problem so he
did two things. He stopped driving with his lights on in the daytime and
he routinely charged the car's battery.
This is what one must be careful of, an alternator running near or at its
rated output before the RV is hooked up. I know the design margin on most
vehicles has improved over the last 10 years but still, one should check
before frying the alternator.
In my MH, the rather marginal alternator wiring gave off a variety of
interesting smells once too often so I cut it out and wired the alternator
directly to the house/cranking interconnect relay. This relay is wired
with #0 cable so it is the same as a direct battery connection.
My alternator is rated at either 80 or 90 amps (can't recall at the
moment). My E-meter shows 75 amps to the house battery after a day's dry
camping. I don't know what the chassis draw is but I'd bet at least 20
amps, more with the AC blower on.
I've smoked 5 or 6 alternators since I've had this RV. I finally removed
the diodes and reg as I described earlier and so far so good. That Leese
Neville alternator in that picture I posted is destined to go in the rig
just as soon as I get a round tuit and get some mounting brackets
* Ford DID put a huge alternator on this car, obviously heavy enough to
handle its rated output continuously. Probably because of the thin film
From: John De Armond
Subject: Re: Propane vs diesel generator
Date: Fri, 30 Sep 2005 20:35:06 -0400
On Fri, 30 Sep 2005 19:30:54 -0700, "(PeteCresswell)"
>Per Neon John:
>>I installed a separate deep cycle battery for the inverter. I also
>>have a 200 amp alternator on the truck so keeping up with the thing
>>isn't a problem. Keeping up only really matters if you're running a
>>large load for a long period of time. For stuff like running a circle
>>saw and the like, the battery provides the surge current.
>>If you need to run a heavy load for an extended period, you can get
>>"ambulance alternators" up to about 250 amps that will fit on the same
>>mount as your old one. A serpentine belt will handle the load. V-belt
>>setups generally need two belts.
>Are there implications for the alternator in running an inverter? I've blown a
>few alternators just giving people jump starts.
Yes. Car alternators generally (huge generalization) can't handle
much more than half their nominal rating continuously. If that kind
of service is anticipated then some sort of heavy-duty arrangement is
required. One thing I've done in the past is to move the diodes and
regulator out of the alternator case to a place where they can run
cooler. The semiconductors are the weak points. The windings
themselves can handle the load.