What is the best way to set up an alternator/battery system?

  • Auto/Motor
  • Thread starter Captain Mike
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  • #26
i found these guys' introductory page informative.
https://www.zena.net/htdocs/alternators/alt_inf.shtml



Woke me up to the cooling problem.
Might that be what burned up your first one? How was it ventilated ?

I think i'd investigate propane refrigeration, too.
The first generator setup was ventilated by several fans circulating, according to the formula I found, more than 5 times the air movement necessary. The generator worked multiple times for many hours longer, in hotter conditions than when it burned up. (After extensive reflection upon the event I've concluded it was for the best... Better than the generator burning up at a location with 200 lbs. of LP on board, me and my crew on board with 1000 or so dollars of food, the liability issues that could have happened plus the dozens if not hundreds of phones recording the bad press... so...) I'm interested in implementing something that will work all the time.
I have been reading into 240 volt alternators that can pump out the needed wattage. Would that work? A 240 volt vehicle alternator. I found one that says 100kw.
1.) Do all vehicle alternators put out DC power?(The ones I found don't specify)
2.) Would a 240 volt alternator pumping out the needed amount of watts, going to a distribution panel like in a house, being split into 120 volts be a proper thing to do? That is why I'm curious if all alternators put out DC power and if so...
3.) What would be the best course to convert that to the proper AC power?

Again, I thank everyone for their feedback and advice on the best course of action.
 
  • #27
Tom.G
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Alternators are called that because they put out Alternating Current (AC). They are also called AC generators. Generator is the generic term for something that puts out electricity, whether it's AC or DC.

In automotive usage, the electrical system is DC, 12 Volts for passenger cars, usually 24 Volts for large heavy duty trucks. Alternators are used these days because they are mechanically and electrically a bit simpler (lower cost) than DC generators for the higher output currents needed for the present vehicles. To charge the batteries, the Alternator output is fed thru a Rectifier to convert the AC to DC. Often the rectifier is built into the Alternator.

Avoid using an inverter if you can, they are expensive. In many instances, since Alternators inherently put out AC there is little point in converting to DC then back to AC. The drawback of not using an inverter is that the Frequency of the alternator output is directly proportional to speed. This means a governor is needed to keep the engine speed constant to get the correct frequency. For instance if the alternator is spinning at half its nominal speed then the frequency, instead of being 50Hz or 60Hz, will be 25Hz or 30Hz. That's OK for resistance loads like an electric heater or stove but it will burn up most motors.

The 100kW generator you found would need 130HP to 150HP to drive it at full load. That is probably around ¾ throttle of the vehicle engine. If it is self powered it would need an engine of at least 150cu.in. or 2500cc. displacement, larger if you don't want it running full throttle.

If you really need 100KW of power you are in the range of hauling around a trailer with a generator and its engine. Clumsy in city traffic.

Hope this helps.
Tom
 
  • #28
256bits
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i found these guys' introductory page informative.

.
For example: An alternator producing 100 amps produces four times the heat of one producing 50 amps. A 200 amp unit will produce four times the heat of the 100 amp model -- eight times more heat than the 50 amp model!
Wondering about what they wrote.
Shouldn't that be the "the same alternator " for a comparison of 100A and 50 A output heat production - ie I2R heat produced in the windings.

A 200 A unit should have, one would think, thicker wire than a 100 A unit, I don't think that comparison is completely justified to say 4 times more heat production.
Double the length of wire, but with thicker wire makes a larger unit, and hence a cooling problem to get all that heat out from the interior.

It should be noted that the heat production through the diodes is fairly linear with Amp output, regardless of same alternator, or different alternators.
Another heat dissipation problem.
 
  • #29
Tom.G
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As @256bits pointed out, there are some problems with that website.

For example: An alternator producing 100 amps produces four times the heat of one producing 50 amps. A 200 amp unit will produce four times the heat of the 100 amp model -- eight times more heat than the 50 amp model!

50A unit . . . 1 heat unit
100A unit . . 4 times heat of 50A, or 4 heat units
200A unit . . 4 times heat of 100A, or 16 heat units "-- eight times more than 50A unit"

Are we playing "Whack-A-Mole" here?
 
  • #30
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A PTO like what @anorlunda suggests is a good way to go using a truck engine as power source. I'm having a hard time envisioning fitting the required number of off-the-shelf alternators under the hood, and belting them to the engine shaft. If not a truck engine-driven PTO then an externally driven genset may be the best option.

1.
Mounting the generator on the outside is NOT an option. No-one will be able to hear anyone order anything.
Is a low noise requirement the only one nixing having the generator on the outside?

If so, perhaps a noise reduction enclosure brings an external generator back into the game. This isn't an endorsement, but went poking around, and found a manufacturer, Zombie Box, that serves this market. The Duromax XP12000EH generator is rated for 74 dB or less of noise production. Their X-Large noise enclosure provides a minimum 16 dB reduction.

2.
I DID have a gasoline/propane generator that had what they said an "internal failure" and it burned down half of the old vehicle.
Is it possible to find out the nature of the "internal failure"? Was it on the fuel system/engine side, or an electrical issue?

About how many hours of run time did the generator have? The manual calls for various inspections and component replacements on 150 and 300 run hour intervals, which is roughly every 3 to 6 weeks for an 8 hour operating day.

3.
Chest freezer, freezerless fridge, hotbox, steamtable, heatlamp, hoodvent, fridge/freezer, sandwich table cooler, the small amount of power for the water heaters electrics (It's fuel is LP), lights, and 2 water pumps (one of which is gray water and won't be used when we are serving so I didn't count that. It works out to roughly 9,375 W with everything running peak (that is with the chest freezer in the higher amp "startup" and the hood vent motor on high which on our last vehicle we didn't need it on high)
12000W peak/9500W continuous rating applies to generator operation using gasoline for fuel, and derates to 10200W peak/8075W continuous running on propane.

Electrical loading was close to generator rating, and may have exceeded it upon occasion.

4.
The generator did have a low voltage trip.
Was this added later? No mention of a low voltage trip is made in the XP12000EH operator manual, it isn't shown in the electrical schematic, and none of the photos show a low voltage trip indicator.

Can't say for certain, but with a generator running close to full output the possibility exists it could run hunky-dory so long as only one or perhaps two of the fridge/freezer compressor motors turned on at the same time, but if all three turned on at the same time for voltage to drop enough to prevent one or more of the motors from coming up to speed, continue to pull high startup current, and (without undervolt protection) cause generator and/or motor failure.
 
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  • #31
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A generator is the combination of an internal combustion engine (ICE), an alternator and an electrical system to transform the current into something useful (voltage, for example). You need everything except the ICE. So if you can get the alternator and the electrical system from a generator that is known to work well and safely, all you have to do is connect this alternator to your truck engine while making sure the alternator will turn at the proper rpm. That's it. You don't have to customize your own system and wonder if you have the correct parts. The electrical system (alternator included) already works with the ICE, it will also work with the engine truck.

You may not have talked about a generator for the food truck, but others have mentioned it. I was just giving a real life example of a safety issue for anyone reading this thread and thinking it is a good idea.

It all depends on your needs. A quick search shows that the largest alternator for a truck is 320 A @ 12 V. That is 3840 W (= 12 X 320) of power. Is that enough power for your needs? You still need some electrical system to convert that current to something useful. I doubt you are using equipment working with 12 V direct current, which is the alternator output. If so, great, you only need to change the current truck alternator to a bigger one!
I wondering if that 12V 320AMP alternator you've mentioned, suitable for any truck, how do I find out that I can use some model with my truck?
 
  • #32
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I wondering if that 12V 320AMP alternator you've mentioned, suitable for any truck, how do I find out that I can use some model with my truck?
It's a bit expensive (~$725 USD) -- I'm thinking about buying one for my 1985 4.8L inline-6 Chevy P30 Step-Van -- look up '6-phase versus 3-phase' if you're interested -- you might need a different regulator, too -- as others have pointed out, it may not be the best way to generate electricity -- I have a 3.5 kw gasoline-powered generator with a Honda engine (less loud than some others), but I think it's probably a good way to do it if you're going to use your truck's engine to do the side job of providing electricity -- https://www.droppinhzcaraudio.com/p...f-exciting-chrome-w-march-1-75-pulley-and-fan

1584440508475.png
 
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  • #33
anorlunda
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I'm thinking about buying one for my 1985 4.8L
That's an impressive alternator. You will also need a special 6 groove serpentine belt and a new crankshaft pulley to match. The description says that it is designed to work at 800 RPM idle speed.

I'm not a M.E., but I would guess that this must stretch the limits of pulley-belt power transmission with its small diameter, low RPM, and high power.
 
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That's an impressive alternator. You will also need a special 6 groove serpentine belt and a new crankshaft pulley to match. The description says that it is designed to work at 800 RPM idle speed.

I'm not a M.E., but I would guess that this must stretch the limits of pulley-belt power transmission with its small diameter, low RPM, and high power.
Yeah -- there's a lot that goes along with it -- but that engine can produce enough power -- you make some adjustments, and it'll work -- I'm looking at a 2-alternator option set as well . . .
 

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