Typical charging rate of a car battery (from alternator)

Most are only in the 150 - 200 amps. Any higher and the wiring requirements go way up.

The LN alternators are also BIG HEAVY units. Rated for high output at lower rpm than the auto units.

FYI you should have an 80 amp unit in the Fit and a 100 amp in the Frontier.

Those are MAX output with proper cooling at 2500 - 3000 rpm.

Reply to
Steve W.
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"Steve W." wrote in news:k6vppg$afo$ snipped-for-privacy@dont-email.me:

You certainly wont get proper cooling without adequate airflow and the designers were almost certainly counting on vehicle speed to provide a good part of that.

IMHO this application would REQUIRE an external alternator controller (available commercially) with a temperature sensor on the alternator housing and probably a ducted in cooling air feed to the rear housing.

Reply to
Ian Malcolm

However you do need to take the resistance of the wires into consideration.

#4 copper cable, for example, has a resistance of 0.253 per 1,000 ft at 68 degrees F. .308 at 167 F. 1 amp current through this "resister" results in a voltage drop of almost 1/4 volt. 10 amps results in a drop of 2.5 volts. or about 20% losses. Your 12 volt circuit suddenly becomes a 9 volt circuit. So at low voltage you require large, expensive, wires to avoid significant voltage losses.

A 120 VAC circuit using 1,000 ft. of #4 wire with 10 amps flowing through it would have a voltage loss of about 3 volts, or about 2.5% so with conventional AC circuits you can use smaller, cheaper, wires.

Reply to
John B.

I don't really think that's it--I just went and looked at replacement alternators listed for Chevy Lumina -- of 10 or so the amp ratings ranged from one at 85 to 140 w/ the bulk at 100-105A. I've never had any problem in any vehicle of recharging a _good_ battery from discharged condition as long as there wasn't something else wrong (like a bad regulator, etc.)

Any one vehicle may be built w/ the lower amp-output, of course, but these days w/ the advent of A/C and all the other electrical accessories as standard equipment more often than not the alternator is far larger than on vehicles of yore (say '60s/early '70s and earlier, particularly).

Reply to
dpb

But they don't put those bigger models in on basic vehicles with no AC, do they?

Reply to
Michael A. Terrell

All good to know. And I always note wire sizes in inverter specs. Always considered wire costs to be significant to reduce losses going to the inverter. But I've booster cable jumped a lot of cars, and just naturally know that cheaping out on cables is a bad move. I was looking at cables in the 1/0 - 4/0 range and it looked to me that jumping a step in cable diameter would easily compensate for the resistance increase jump from 3 to 6 feet, and still meet a particular inverter's cable specs. I just disagreed about routing heavy cables to my car interior for an non-permanent, "as-needed" inverter setup.

Reply to
Vic Smith

On 11/2/2012 9:46 AM, Michael A. Terrell wrote: ...

How many vehicles are sold in the US _w/o_ AC these days? Very small percentage, I'd wager...

But the 85A was the _smallest_ in the list of compatible for the vehicle class mentioned (out of nearly 20 choices) and there was only one of them in the first 10 or so of the list (ordered by price) that I actually paged through that was under 100A. That indicates that anything under the 80-some A class is pretty limited to me...

I'm sure you can still find 50 and 60A ratings but even they shouldn't have any problem charging a battery as long as the rest of the system (and the battery) is in good shape.

IOW, I suspect something else was the underlying culprit in the preceding comment of killing alternators...

Reply to
dpb

250 amp is pretty standard. The units Leece Neville/Presolite builds for fire trucks are 270 amp. (Series 4800 and 4900)

The AVi 160 used in school busses is a 210 amp unit.

Their largest unit is 325 amps (2270 or 2272 series)

Never seen or heard of a 500 amp alternator for vehicle use.

Reply to
clare

Those 100 to 140 amp units are only good for that kind of output for a VERY short time - untill they get hot, and die.

Reply to
clare

Those old alternators were designed & rated for continuous service. Today's 100 amp is an old 37 amp with Schottky diodes instead of Silicon diodes. They have a lower forward drop, and can handle more current in the same size package.

Reply to
Michael A. Terrell

Another thing to keep in mind is that the output of the alternator might be 325A, but if the battery is down 2 volts that's ony 650 Watts output (less than 1 HP).

Reply to
Michael A. Terrell

A bad battery will do it - REAL QUICK.

Reply to
clare

That's about the biggest *practical* unit I've seen also. They put those on the Semis when they used to plaster them with 500 marker lights and they were all incandescent.

Oh, and they did use the 300A ones on the new Disneyland Parking Lot Trams - a tractor with a Cat 3208T on Natural Gas, and a string of 7 passenger trailers with overhead lighting in all the cars. Just a little bit of alternator load...

Now that they've gone to LED's it cut the power draw by about 75%, and they can get by with the normal factory-option 'heavy' alternator in the 200A range.

The best way to make an Inverter Rig like that for your house is to get a larger gasoline engine, like perhaps a 13-HP to 18-HP Briggs with the flyweight speed governor for generator set use, find a sheave to fit the crankshaft, and couple that to a truck alternator and a big deep-cycle battery - preferably two GC-2 Golf Cart batteries in series.

The governor part is very important, you can't chance setting the throttle by hand - if the belt snaps and the load dumps from the alternator you can overspeed the engine and blow it up. The air-vane governor on a Lawnmower-duty engine will work kinda sorta, but they'll 'hunt' and 'surge' on you while working. But most small car engines that you would repurpose into a prime mover don't have any sort of governor built in at all - you have to add one.

For small overnight loads you can run off the batteries, but you want the engine running before you crank up the microwave oven, or start charging your cellphones and Laptop battery.

Put it on a cart with wheels, add a pair of 4/0 Truck-sized Jumper Cables (and a 300A or 500A circuit breaker in case of an "Oopsie!"), and you can boost-charge and start almost anything from a Semi to a D-9 Dozer to a Liebherr mining dump-truck or a Locomotive.

Note that when the engines get really huge they are often 24V electrical systems. Or they have an Air-Starter, and you need a gas-engine air compressor on a cart to give them a jump-start.

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Reply to
Bruce L. Bergman (munged human readable)

Yeah, that was mentioned -- big bummer too.

Good points, more big bummers.

The devil is in the details, and what initially seemed like a slam-dunk no-brainer has become quite problematic. I'm looking to replace my (stolen) BlackMax with a tri-fuel -- just bite the bullet, and go thru all the sound-proofing, plumbing, and electrics to the panel. And put a chain on it... I'm still going to fool around with a big-ish inverter, just to see what can be made of it.

A good fraction of the Sandy victims will not have power 'til Nov 11 or so.... holy shit.... And more salt-in-wound: Linemen from other states have arrived, to a massive gas shortage, and are essentially immobile.... it just never ends.

Reply to
Existential Angst

I'd like to see the rectifier and regulator for a 500 amp unit!

When we got the latest rig (E One built on a commercial chassis with no electrical upgrades!) I stuck a spare LN unit I had on it. The original dept was always complaining that the low voltage alarm would go off and they had to rev up the engine to bring it up (which is SOP in most departments anyway, even the big units don't put out enough at idle to power all the lights on the new rigs)

Only real problem I had was the crappy wiring that I replaced with heavy duty stuff. Just bugs me to see low grade crap on an emergency vehicle.

Reply to
Steve W.

Use the GC2H - 235ah - one inch taller than a GC2 and the price difference is less than the capacity difference at my local supplier.

Reply to
clare

I worked as a engineering tech with Autolite in the mid 1960. They originated the commercial automotive alternator for Chrysler. I can honestly tell you that if an alternator was rated at 60 amps at 14.2 volts it will put that out, for about the first 5 seconds of testing, thereafter degrading quickly because of heat and in most cases were not capable of continues max um output for longer that 1/2 or 1 hour without sever over heating.

Reply to
KG

I just did a couple quick calc's and here's what I got. Assuming a regular setup first with the battery sitting at 12.5 volts, which is reasonably well charged, and with an internal resistance of 0.08 ohms. V=IR, doing the math gives you 25 amps if the alternator spins fast enough to put out 14.5 volts while it's charging the battery. That's based on the 2volt difference between the battery voltage and the alternator voltage. Add a second battery with the same state of charge at 12.5v and the parallel resistance value calc's to 0.04 and the math gives you 50 amps from the alternator.

If the two batteries were down to 12.0 volts, which is a fair discharge level, you get a final value for both batteries charging of

62.5 amps. If those assumptions are in the ballpark it doesn't seem to me that adding a second battery that's 50% discharged would be that big a deal IF charging the batteries was the only thing going on. If you are driving around and using 30 amps to run the car, stereo, AC system then you are pulling over 90 amps and I suspect most standard alternators don't like cranking out that much power for very long.
Reply to
Ashton Crusher

FWIW, CoorsTek, a major ceramics company, is a different company from Coors Brewing. They used to be under the same parent company and the ceramic business derived a large percentage of its income from support services for the brewery but they separated in 1986. I remember back in high school in the late '60s thinking it humorous that the crucibles we used in the chemistry lab were labelled "Coors".

Reply to
J. Clarke

The 1" Sony VTRs we used at Ch. 55 (WACX), a Christian TV station in Orlando, Fl. were bought from Coors marketing unit where they produced their commercials.

Reply to
Michael A. Terrell

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