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

[Captain Mike]

Hello, I am a food truck owner and I recently had a situation which made me rethink my power needs for my kitchen on the food truck. I have a 2001 Workhorse forward control Stepvan and I wanted to run an alternator, batteries, and an inverter setup INDEPENDENT of the trucks own alternator and electrical system. I first thought of using a high capacity alternator and just running everything off of that because I was reading about how difficult it may be to couple two alternators together, however the best option for my needs would be to have two separate electrical systems. I am hoping someone can help me figure out the best and safest course of action. Thank you for reading and I thank you in advance for any advice.

 

[russ_watters]

[moved to DIY Projects]

Hello, I am a food truck owner and I recently had a situation which made me rethink my power needs for my kitchen on the food truck. I have a 2001 Workhorse forward control Stepvan and I wanted to run an alternator, batteries, and an inverted setup INDEPENDENT of the trucks own alternator and electrical system. I first thought of using a high capacity alternator and just running everything off of that because I was reading about how difficult it may be to couple two alternators together, however the best option for my needs would be to have two separate electrical systems. I am hoping someone can help me figure out the best and safest course of action. Thank you for reading and I thank you in advance for any advice.

Welcome to PF!

Could you explain more about your requirements (120V? kW required? How many kWh per day?) and the idea you have for meeting them? I see several ideas there that don't appear to go together well.

...the obvious choice, to me, would be to buy a normal stand-alone generator. It's certainly more efficient than an idling van. The only reason I could think of for using an inverter and batteries is if the daily requirements are so low you can get away with using one or two deep-cycle marine batteries to power the kitchen. I don't think that's likely, but it may be possible.

 

[jim hardy]

however the best option for my needs would be to have two separate electrical systems.

Simplicity is usually a good thing.
Separate systems eliminates need for interfacing them
but the physical task of mounting a second alternator is daunting to those of us without access to a machine shop.
Fortunately the audio guys with their preposterous subwoofer amplifiers have created a market for such a thing.

try a search on "dual alternator bracket"

 

[gleem]

I agree with @russ_watters . a portable generator. 1KW is equivalent to 1.3 hp. You don't need to run a 200hp engine to produce a few kws of power. It is probably bad for the engine too.

 

[jim hardy]

You don't need to run a 200hp engine to produce a few kws of power. It is probably bad for the engine too.

yep.

There do exist propane fueled generators for RV's
their exhaust is less annoying than gas or diesel
and you likely have propane on board for the kitchen anyway ?

 

[anorlunda]

I'll fourth the vote for a separate generator.

Among other reasons, many localities forbid sitting with the vehicle engine idling.

But @gleem's reason was the best. Your $10,000 engine idling has about the same lifetime (measured in operating hours) as a $1000 generator. That makes it a no brainer.

(There is a counter-example of NYC Checker Cabs that got 700000 miles on their engines because they never allowed them to cool off. But I think that example is so ancient that its validity today is doubtful.)

 

[Captain Mike]

I appreciate the feedback. I'm not saying what I wrote is correct or the actual parts I need. I have read articles of people who have used the idling engine, high capacity or coupled alternators, and battery banks to power their food trucks, many with solar panels to help supply power. I also will NOT be using a regular stand alone generator.. again. Seeing as the first one had an "internal failure" and burned down half of my previous food truck. That $1000 generator burned down 25,000 dollars worth of stuff and cost a year of work and "progress". Plus I need roughly 10kw to run the entire kitchen at any given time. The propane generators for RV's that I have found are roughly $1 per watt... $10,000 dollar generator will not work for me. I've read a few things on people that use the alternator, batteries and idling engine method and it works well for their purposes, and is MUCH quieter than the easy, traditional, and annoyingly loud generators sitting on a bumper. However all of these texts just say "high capacity alternator, or coupling alternators" but they don't specify where or how they had that accomplished. Maybe it was a converter and not an inverter? I'm not saying I have the proper terminology, I'm just inquiring about more detailed information on a system I know people use and works well.

 

[anorlunda]

Plus I need roughly 10kw to run the entire kitchen at any given time.

10000 watts/12 volts = 833 amps. The biggest alternator I find online is 300 amps. You would need 3 of those, plus your existing alternator. 300 amp alternators are about $700 each. I'm skeptical that you could mount 4 of them in your engine.

Short answer, 10KW is too much for an extra-alternator solution.

I see on Amazon that you can buy a 12 KW propane/gasoline portable generator for $1059, not $10000.

Portable generators should be located outside the structure because of CO and fire hazards.

Are you running electric stoves? That is far less efficient and expensive than using propane stoves or ovens. Electric stoves/ovens are a poor match for mobile applications.

 

[jim hardy]

I need roughly 10kw to run the entire kitchen at any given time.

sounds like you're using electric cookers ?
How do you power the present setup ?

The propane generators for RV's that I have found are roughly $1 per watt... $10,000 dollar generator will not work for me.

yeah, a fellow needs to find something that's made for the masses.

my first Google hit

 

[russ_watters]

Seeing as the first one had an "internal failure" and burned down half of my previous food truck.

Portable generators should be located outside the structure because of CO and fire hazards.

Not much to add except to second that.

...also, there is no battery+solar solution that can provide 10kW all day for a food truck. It's way too much energy. Perhaps people who have done that are using propane for the grilles and only using the electricity for the other appliances. I'd bet 80% or more of the energy a food truck uses is for the cooking surfaces.

 

[CWatters]

Most mobile food vans in the UK use a free standing portable generator a few meters away from the van. One advantage is that if a power socket is available you just plug into that instead of the generator.

The other approach is to use batteries for lighting and gas cylinders for cooking.

 

[CWatters]

10000 watts/12 volts = 833 amps. The biggest alternator I find online is 300 amps.

I think it would need to be at least a 48V system.

A 10kw continuous duty inverter won't be a super cheap item. Only one I could google was US $3000.

I'm wondering if there are alternators for catering vans that produce 220V directly. No battery or inverter required. There would need to be some sort of throttle control.

Think this route is a job for a specialist conversion company.

 

[anorlunda]

I think it would need to be at least a 48V system.

A 10kw continuous duty inverter won't be a super cheap item. Only one I could google was US $3000.

I'm wondering if there are alternators for catering vans that produce 220V directly. No battery or inverter required. There would need to be some sort of throttle control.

Think this route is a job for a specialist conversion company.

That works too. https://www.ebay.com/itm/WinPower-PTO-Powered-Generator-10kw/163439582159?hash=item260dc21bcf:g:MwkAAOSwOcpcGbFs is one that works from a power take off. About $1500. I presume it is an induction generator. For 10 kW, PTO sounds more practical than belt driven.

 

[gleem]

Regarding the failure of your first stand alone generator and the subsequent damage it caused. That should never have happened if you had proper breakers or fuses installed.

What do you need 10KW for? Are you using an electric grill/stove?

Another point I do not understand is the desire for batteries I assume for backup If you need 10kw and maybe need one hour storage you would need 9 - 220AH ^† batteries with a total weight of over 1000 lbs. at an approximate cost of about $2700. not including inverter and cables/hookup. Even if you only need the battery for an orderly shutdown say of less than 7 minutes you still need about nine batteries to be able to deliver the 833 amps assuming you can only draw about 100 amps from each without damaging the batteries.

† It is recommended for standard flooded cell batteries you do not discharge them more than 50% capacity in order to maintain the longest operational life.

 

[Captain Mike]

I am using propane for the stove/oven, fryer and the water heater. I DID have a gasoline/propane generator that had what they said an "internal failure" and it burned down half of the old vehicle. The generator Jim Hardy suggested is the exact one that failed. Mounting the generator on the outside is NOT an option. No-one will be able to hear anyone order anything. We tried it with that last generator. The generators I am talking about roughly a dollar per watt are RV internal propane generators, RV...RV... not stand alone generators... Not the ones you wheel out and put next to your vehicle. Also with the information I was reading they converted the power to AC. (Hence the inverter or converter question.) Similar to a boat. CWatters I was reading about 48 volt systems. I hope people understand that I'm asking for what would work and not claiming that the idea I have is valid. I appreciate the concern but how about everyone please stop worrying about how much it costs, initially, and fuel costs. (Those are my problems.) I GREATLY appreciate all the feedback! Thank you everyone!

 

[gleem]

So what do you need 10KW for?

 

[Captain Mike]

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) The grilltops/oven, fryers, and water heater are L.P. … So if I am running the system I wouldn't NEED batteries? I was planning on having them to provide at least a few minutes of battery backup if something should happen. (Planned on 3) Gives us a few more minutes to get the support truck there to empty the food. Plus, all the inspections and opinions I received before and after the fire from professionals and non-professionals on the generator claim that all the wiring, fuses and all were done properly throughout The pros determined it was a fault within the generator. Implying to me that it wasn't built 100% right.

 

[gleem]

Wow. Anyway you would want to carry on service for the current orders. Turn off all unnecessary appliance to take care of current customers re-figure your power requirement to determine the required back up batteries.

Getting back to adding alternators to your truck, something not mentioned is that the output of an alternator depends on the rpm. To get a decent output you would need to run the engine at a higher than idle rpm.

For a portable generator,a power management system that could prioritize the equipment's power use,would seem like an answer by inhibiting some units from starting up at the same time since start up current draw can be three to seven time greater than the running current. I do not know if such a system is commercially available. but if available could significantly reduce you power requirement.

I received before and after the fire from professionals and non-professionals on the generator claim that all the wiring, fuses and all were done properly throughout The pros determined it was a fault within the generator. Implying to me that it wasn't built 100% righ

Did they tell you that low voltage can burn up an AC induction motor. If you load a generator its voltage will drop. Listen to the a generator when you plug something into it. You would have needed an under voltage trip

 

[anorlunda]

I still think the power-take-off generator sounds best. See #13.

It is located outside the vehicle; thus fire safety. (Alternators under the hood can start their own fire.) There is no external engine, so no audible noise to bother customers. It is AC, no inverter needed. It is disconnected while driving. It beats multiple alternators on simplicity.

Are there kits to add a PTO to a truck engine?

Edit: I added an AUTO/MOTOR tag to this thread. That might bring in some members more knowledgeable on the AUTO aspects.

 

[jack action]

All you need is the 'generator end' of a generator. This way you don't have to worry about what is the 'correct' electrical system, since it is already set up. Whether it is turned by the generator engine or your truck engine, it doesn't matter. You need to find the appropriate pulley ratio to match the idling rpm of your truck engine to the alternator designed rpm. The truck engines should try to maintain its idling rpm by adding more fuel as the alternator demand increases.

Edit: You may want to provide a way to disconnect the generator from the engine when you're on the road, i.e. not idling. As the generator will turn too fast in that condition.

As for a generator inside a food truck, one person died this year in my hometown because of that. Something to think about.

 

[Captain Mike]

Wow. Anyway you would want to carry on service for the current orders. Turn off all unnecessary appliance to take care of current customers re-figure your power requirement to determine the required back up batteries.

Getting back to adding alternators to your truck, something not mentioned is that the output of an alternator depends on the rpm. To get a decent output you would need to run the engine at a higher than idle rpm.

For a portable generator,a power management system that could prioritize the equipment's power use,would seem like an answer by inhibiting some units from starting up at the same time since start up current draw can be three to seven time greater than the running current. I do not know if such a system is commercially available. but if available could significantly reduce you power requirement.
Did they tell you that low voltage can burn up an AC induction motor. If you load a generator its voltage will drop. Listen to the a generator when you plug something into it. You would have needed an under voltage trip

The generator did have a low voltage trip. The generator made numerous test runs on a full load during the months before the fire and everything was more than fine. That is why it was surprising to me. The "portable generator" will NOT be an option for our situation.

 

[Captain Mike]

All you need is the 'generator end' of a generator. This way you don't have to worry about what is the 'correct' electrical system, since it is already set up. Whether it is turned by the generator engine or your truck engine, it doesn't matter. You need to find the appropriate pulley ratio to match the idling rpm of your truck engine to the alternator designed rpm. The truck engines should try to maintain its idling rpm by adding more fuel as the alternator demand increases.

Edit: You may want to provide a way to disconnect the generator from the engine when you're on the road, i.e. not idling. As the generator will turn too fast in that condition.

As for a generator inside a food truck, one person died this year in my hometown because of that. Something to think about.

What are you talking about "generator end"? and as for the last part. Generator inside a food truck? When and where was that said on my end? The only "generator" of power I am looking to use is the engine for the truck.

 

[Captain Mike]

I understand the engine would need to be running a higher rpm and the pulleys and alternators and such will need to be calibrated to each other. I think there is room for a dual alternator bracket that I'm looking for. I've seen food truck running their engines and no other generators... maybe some solar panels to help. I thank all of those people who are telling me the physical properties and such of what I'm trying to accomplish versus those who offer the cheapest or easiest solution to just "half-ass" my problem. I'm hoping to find the way to give my customers and my crew the best experience. Even if it is a little more expensive or a little tougher to figure out. Thank You ALL for your input and imparting your knowledge my way.

 

[jack action]

What are you talking about "generator end"? and as for the last part. Generator inside a food truck? When and where was that said on my end? The only "generator" of power I am looking to use is the engine for the truck.

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.

I've seen food truck running their engines and no other generators... maybe some solar panels to help.

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!

 

[jim hardy]

i found these guys' introductory page informative.
https://www.zena.net/htdocs/alternators/alt_inf.shtml

Typically, the largest single continuous duty alternator that can be fitted into the engine compartment of a large vehicle is one producing a maximum current of around 200-250 amps. Small vehicles seldom have alternators producing much more than a maximum of 100 amps.

Why? The waste heat that alternators can produce when heavily loaded increases dramatically as alternator output current increases. To deal with this heat, the alternator must become larger -- and, in some cases, also revert to liquid cooling.

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!

To deal with all this heat, a 300A air-cooled alternator balloons in size to be over a foot in diameter, and over eighteen inches in length -- much, much larger, and heavier, than a typical automotive alternator. This forces manufacturers of such ultra-large alternators -- typically used in busses and similar vehicles -- to resort to liquid cooling in order to make them small enough to fit into the very large engine compartment spaces found on this type of vehicle.

This is why most emergency vehicles resort to split electrical systems using two, or even three, large alternators -- one dedicated to the non-stock electrical equipment installed on the vehicle and one (or more) dealing with the load of the vehicle itself -- OR to very complicated isolation mechanisms that allow the output of multiple alternators to be combined to supply power to a single large load.

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.

 

[Captain Mike]

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.

 

[Tom.G]

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

 

[256bits]

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.

 

[Tom.G]

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?

 

[Asymptotic]

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.