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Building a series hybrid generator

45069 Views 118 Replies 35 Participants Last post by  JohnMogs
I know I'm thinking too far ahead as I haven't gotten my EV built yet, but I hope to make it a series hybrid one day. I know a lot of people buy an off the shelf generator and hook it up to the charger but I think that must be rather inefficient and you'd need a powerful charger to make it useful.

Therefore I am investigating what it takes to build my own generator. There are tons of small engines to use. How about the electric generator or alternator? Any low-cost options? I am building a 120V system, so say 130-135V out of the generator system. Could it be wired directly to the battery pack and the current would drive the motor or charge the batteries depending on the load from the EV controller? I know newer car's electrical systems are moving to 42V. Could an off the shelf alternator be "over-clocked" to 130V?

Low-weight would be best, of course. High-efficiency is very desireable as well. how efficient is a small motorcycle engine? How about a used rotary snowmobile engine?

Anyone have any ideas?
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I have thought about the same thing, why not take a generator and put a rectifier on the output. Run the rectifier to the battery pack and adjust generator RPM to match the current you want.

A few known catches:
Generator output would need to be close to pack voltage, this would determine whether you used a full wave bridge rectifier or a full wave rectifier. The very big diodes are going to get hot so you will need heat sinking and this will be a loss.
Your generator RPM will determine amps into the pack, now you need to watch generator temperature and pack voltage. You would not want to over charge your pack.
You would eliminate the generators regulating system that keeps a constant 110/120 voltage AC and you would eliminate the on board charger. This would not be for a novice unless you knew how to monitor generator and battery temperatures, battery voltage and generator current. Things could go very wrong if not applied correctly.
I know it is possible to generate over 120VDC with a car alternator by adjusting the field coils properly. With a high-capacity alternator and a proper voltage regulator to adjust the field it should be possible to adjust the current and voltage out of the alternator as needed. Just measure the current and voltage and it would push out max amps if the voltage was under a threshold, as when the car is driving or the batteries are low. As the voltage increases adjust the field to charge the batteries as recommended. Constant current then constant voltage for lead-acids for example. Watching the temp of the alternator so it didn't get melted down would be a good idea too. :)
How many watts is your alternator rated for? What would you use to power the alternator? Your theory is sound; we just need to work on the details.
Here ( is the kind of thing I'd be looking at. I'd go grab one from an junked truck in a pick-n-pull actually.

130A x 14V or so --> ~2000W. I'd expect that at higher voltages the current wouldn't drop as fast as the voltage, just like the current rating of a wire doesn't depend on the voltage. So maybe at 140V we could still get 50A out --> ~7000W. Almost 10 HP, just the range I'm looking for. Throw a 15 HP small engine on and you're there. The torque on the shaft and the load on the bearings would need to be considered.

I'm not sure how fast it would need to spin. I'd want to figure out the most efficient speed for the engine and the alternator and just use pulleys. I'm not sure how much power you can put across a serpentine belt. Might need larger pulleys on the engine and the alternator to get enough contact area and low enough tension on the belt.

I understand that it is trivial to hook up two or more alternators in parallel and control all of the field currents coils together. Then it would just be adding as many alternators as needed. Better cooling then.
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You are correct, wire size cares more about amperage than voltage, and the wire insulation cares about voltage and temperature. Keep in mind how automotive people rate things, unless they specify a period of time or say "continuous" you have to assume they rated it in peak power. How long would the alternator produce 130A before cooking something? The web site did not give a weight but I think it is less weight than a 2KW generator head which is also rated in peak unless specified. Based on mass alone I don't think 130A continuous would be true.

You can increase field current to raise output to higher voltage but you would need to know the max current allowed for the field. With higher voltage you might be able to squeeze some extra watts out of it.

Parallel is no problem, you would use diode rectifiers on the outputs which would block outputs from interfering with other outputs. Adjust fields individually to match outputs. If you start to string a lot of them together you would want to look at a single larger generator. For a single alternator see if you could couple the engine shaft to the alternator. Engine speed may not be compatible with this but that is where the research on alternator RPM vs. power out comes in.
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you can pick up a pretty cheap generator head on ebay, they all produce an ac current so it's gotta be rectified regardless. best to use a high capacity charger with a high efficiency (>90%) such as the Manzanita PFC-50

any ac motor is also a generator so if you're not willing to deal with the heavy-weight gen heads on ebay (Chinese cast iron)

also keep in mind that you're gonna need a bit stronger motor than it takes to move the car. i found a couple websites that help out in calculated the energy required to move a vehicle at a given speed.
If I could afford the $3000 charger I wouldn't be trying to cobble together something like this. I'm looking for cheap and simple. I don't need enough to run the car at the full highway speed 100% of the time. Even on trips I like to take breaks now and then and I'd love to be able to have my batteries charging while I'm in the bathroom or getting a bite to eat.
I just found a website that's selling engines incredibly cheap, still not as cheap per unit as you could import from china but the best prices i've seen for consumers none the less.
I have wanted to add a generator to the bed of my truck for some time. I found this:

It's a great piece of information on how he took a three phase motor and put a rectifier on top of the motor coupled to a small diesel engine to extend his range. He is shoving 30 some amps of DC right into the 144 volt battery pack. I am planning on building this as soon as my truck is on the road.
this company sells dc generators for charging battery banks in remote locations
You might be able to use one of these generators
they say it can produce up to 14,000 watts and only weighs 10 pound, I'm not sure if thats a continuous rating though.
that is very interesting. basically custom alternators it seems. they claim 275amps max which is probably at 12volts meaning only 3,300watts. stacking them up and wiring them together would take 3 for my instance which is a bit cheaper than buying a mass produced generator. I wonder what the efficiency is.
Anyone have any ideas?
I have a couple,

Look in They usually have lots of engines and generators.

Your talking about building your own, I've seen it done and the major problem with them is they are all NOISY and they VIBRATE. And when you are done, well . . . they are home built. Don't get me wrong I have lots of home built stuff. But sitting in a car for a number of hours listening to a generator run:eek:.

I think the best alternative is to shop for a used RV genset. Onan is one good one. They are silent, compact and well insulated for vibration. they are desigbed for remote starting. Many hav 220 volt taps. 3,000, 5000 to 10,000 watts are not uncommon. Voltage is clean and stable. There are diesel ones as well. They are made to fit into a confined space and just run and run (quitely). They are current and common so parts are available. Every time I've looked on ebay I have seen one or two.

I know that you can scrounge and shop and make up something cheap, but then you have a cheap generator

Just my thoughts.

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I bought a 5.5KW gen head. It has two 100W 15amp outlets with a 220W - 20Amp three prong twist plug. I says it is for belt drive however it is a keyed 3/4" shaft that mates perfectly with the 3/4" shaft of the 20 HP D&D systems motor I have for it. I am going to use it as a temporary energy supply for our well when we lose power (Which can occur a lot up where we live!) to power our well pump. I will be running it off 6 - 6V 229amp batteries for the battery pack along with an Alltrax AXE controller etc. and an Optima Yellowtop D31A for the contactor coil. I can use my initial 72VDC charger to charge the pack when it is not in use. Like I said it is only for emergency water so it is not a long term power station.
I got it for about (US$)580.
Am seriously thinking about the 10KW head... My idea is this: a hybrid pack. Take one nice sized engine of like 22HP (a Kohler horizontal also available at Northern...) the 10KW... and a nice sized AC motor... of about the 18hp size (40 peak)... I imagine if you have to pay for gas, you could effectively, with the right configuration of controller, contactor, etc., get a vast reduction in waste and perhaps get an equivalence of say 60-70 miles per gallon or more with a small car using a standard transmission/transaxle... or if you were to try something like an older Toyota or Mitsubishi van... use a 310VDC battery pack as well for alternate power with this system... at least this is the theory at the present time... I'm a-schemin':D
P.S. the use of the gas engine could be very easily effected by using ones imagination and having some sheetmetal skills... think out of the box!
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I have been looking at these diesel engines for possible use in a hybrid setup. I was especially interested in the noise suppression enclosure for avoiding noise problems associated with many aftermarket engines. THey offer both single cyclinder and twin cylinder versions. Thought you might want to check it out. Hoping to use only on longer trips.

link is to smaller engine, also check out larger.
You might be able to use one of these generators
they say it can produce up to 14,000 watts and only weighs 10 pound, I'm not sure if thats a continuous rating though.
this is my first post so if i do anything wrong let me know.
I am new to the entire ev process but really want to build a hybrid jeep. this link seems to be the answer to properly run a small c.a.r.b. diesel type generator setup. but i have a question of any qualified person on electric in general. judging from the material provided by the seller their graph shows more rpm= higher voltage and amperage but not quite enough to charge a 144v system. my question is if you conected two of them to half the battery pack and spun them to proper rpm for a little more than 72v ea. would they interfer with ea. other or would they properly charge the whole pack? also would they self regulate and not overcharge the battery's just like a standard 12v alternator? my idea is to install some kind of switching unit that would cause the diesel( to be powered by veggie oil ) to come on at 70% dod and shut off at or approaching 100% charge.
You might be able to use one of these generators
they say it can produce up to 14,000 watts and only weighs 10 pound, I'm not sure if thats a continuous rating though.
The item you referenced is not a generator, it is an 'inverter'. It is rated at 1400Watts. It takes the 12VDC xAmp input and creates 110VAC (at xAmps). They are used frequently to power things like computers/laptops, TV's, shortwave equipment, cameras what-have-you,.. from either connecting the inverter directly to the battery of a vehicle or using an adapter for the 12V outlet (cigarette lighter) in a vehicle. I have a 2200Watt adaptor that I can use for my chainsaw sharpener or a TV/computer out in the field, in my F250 or when I do an over the road in my Toyota for the camera. Handy little critters but in an EV they tend to draw a LOT of amps from the pack or the system battery. Can be practical in a pinch though!:D
no scroll down the page the link takes you to. it is a pma alternator
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