[flapjakpat]

Has anyone ever tried to split the power demand for the electric motor between an alternator and the batteries?

I have some questions regarding this. I am trying to do a diesel electric hybrid, and originally I was going to use 10-12 batteries to get the voltage and amperage demands. However it will cost less, and weigh less, if I can get away with using less batteries.

My thought then is to hook my alternator to the controller, and the batteries to the controller. Would the controller share between the two sources to get the voltage and amps required? (ie, because the alternator will only provide 12V and 150A, the batteries will provide the rest, only when needed?)

Another method I was considering would be to wire the alternator into the battery pack (bypassing the charger?), and have the controller pull from the batteries. Would I need a full battery pack, or would the controller still pull from the alternator while bypassing the batteries, in order to prevent the batteries from being discharged?

I would love to be able to speak with an expert on this subject in more detail. I also would need to know how to do all this safely.

Thanks for all the help!

 

[Ziggythewiz]

What you're proposing is how most hybrids work, but they use a dedicated generator instead of a typical alternator. If the motor is pulling more than the generator puts out, the batteries supply the difference. If the motor pulls less than the generator puts out the batteries get charged.

 

[flapjakpat]

Well that's what I am thinking. What I want to know I guess, is whether or not this works based on way I want to wire it, or does it work like that for some other reason (ie some computer management system)?

Is there a resource I can use to see how other people have wired it? (ie wiring diagrams ) or are there parts lists I can gander at?

Thanks again,

 

[Ziggythewiz]

how exactly it works depends entirely on how exactly you wire it. The connection is pretty straight-forward, the only real variable is how you're turning the generator on and off.

If you can find someone who's done a DIY hybrid, I'm sure they'll be happy to share their details. Most of us don't consider it a very efficient setup. We prefer all electric.

 

[MN Driver]

Either you are trying to do this to add an additional 12v to your system, which is going to be inefficient and you would be better off adding another 12v of battery to your system, not to mention what happens when you try to pull more than the alternator is supposed to put out. Alternators are quite inefficient and using a DC-DC instead will be a better choice.

...or "Another method I was considering would be to wire the alternator into the battery pack (bypassing the charger?), and have the controller pull from the batteries. Would I need a full battery pack, or would the controller still pull from the alternator while bypassing the batteries, in order to prevent the batteries from being discharged?"

It almost sound like you think you are going to extend the range with the 'in order to prevent the batteries from being discharged'. Is this what you are thinking?

I might not be reading what you are saying properly but you'll end up with less distance traveled versus just using the 10-12 batteries you are planning to use either way. Lower nominal voltage but you'd get better range. If you want more voltage, use slightly smaller batteries and hopefully you can fit enough to get the same taget capacity.

If this is just to replace the 12v battery that runs the lights, contactor, etc. you are better off using a DC-DC converter to do that than an alternator. I still prefer the idea of having a 12v battery to buffer that load, even if its a $20 wally world mower battery.

 

[flapjakpat]

Well what I am doing is using a diesel generator to charge the batteries, and power the electric motor. I don't want to directly connect the diesel shaft to the electric motor's shaft because, besides the complexity, I want to run the diesel at its most efficient rpm.

I will be able to travel much more distance using less batteries because I will not have the weight. I will use the diesel fuel to travel much greater distances than an all electric setup. I want to use the batteries as a buffer for the energy created by the diesel.

Also electricity in Fairbanks, AK, is much more expensive than most other places so it is not cheaper, and the way it is produced makes it not any great deal less polluting.

I haven't seen an alternator for an engine that puts out high enough voltage, so I might end up using a generator? I am not sure how this works either. Can I use a 12V alternator to power a 144V system?

I was just planning on running the IC engine manually. My concern though is that when the batteries are topped off, and the motor is not being used (traffic) then I will burn up the alternator.

 

[McRat]

If it's a diesel pickup, many have a dual alternator option.

Also, note that some (most?) have a PTO option on the transmission. The PTO is how high power devices are hooked into a transmission.

Now, the biggest 12v alternators are 200 amps (aftermarket), so figure if you run TWO of them, you can make 7HP worth of electricity. Why bother?

Now, any digital fuel injection cars/trucks cannot survive voltage drops. Most will shut down the engine if it hits 10vdc. When you draw current from batteries, (especially lead acid), the voltage drops. Try to pull 40HP from a diesel pickup via an electric motor, and the engine will shut down in short order.

IMO, you should NOT combine the systems. Run 1 alternator for the engine, and 1 for your recharging, but now, you have 3.5HP worth of recharging.

Best bet is to do it via the PTO, which can handle a serious generator/motor.

 

[McRat]

I'm going a different route though. I don't want to suggest it because it might be dangerous for street applications.

 

[GizmoEV]

If the generator you use will max out at a particular voltage and you size your battery pack so that it is full at that voltage then you won't run the risk of overcharging the batteries.

As for efficiency, if Fairbanks gets its power the same way Glennallen did then I doubt your rig will pollute less than a pure EV. I don't know about cost. When my parents lived in Glennallen they paid about $0.18/kWh. I'm sure it has gone up since then.

A pickup like an S-10 will use 300-500Wh/mi. Taking the high side of 500Wh/mi would mean that at $0.18/kWh the electricity cost would be $0.09/mi. What do you think the fuel cost is going to be to run your hybrid?

 

[McRat]

Things to consider about a diesel hybrid:

Diesels are already 20% more fuel efficient than gasoline for the same HP output. The number is higher if you can run steady state at the torque peak. 40%?

They have no throttle, hence very little engine braking. The regen power on a downhill side of a mountain would save the brakes and generate significant power. A typical diesel pickup weighs over 7000lb and is often towing 10,000+ lbs.

Currently, they are doing transmission tricks, and using VNT (variable turbine) technology to burn off the huge load on the brakes going downhill.

For light diesels? In the US there is little if any market for them. Few companies are making any serious money selling small diesels. Over 90% of the consumer market of diesels is heavy duty pickups.

For industry, diesel-electric propulsion is very common. Too expensive for the consumer market, and currently too heavy.