Help with Hybrid Prototype

What is your projected range on 5 liters of petrol?

Hi Haris,

While this isn't my area of speciality, I just wanted to check you haven't made a fundemantal mistake.

You've mentioned the weight of the vehicle won't exceed 70 kg, and lower you discuss the power requirements and torque required to provide motive force to drive the 70 kg's.

Does the total vehicle weight of 70 kg's include the driver ?

Kind regards and good luck,

Anthony

No !! driver weight is not includeded!!

Unless I misunderstand your project, I think the driver weight should be included. As the moter has to move not just the weight of the car, but also the weight of the driver and any cargo the vehicle is carrying.

Good Luck

There are many hidden assumptions that are built into any answers you'll get for this type of question.

So, perhaps it's useful to consider one end of the possibilities eg "The pushbike". You know the typical system weight, its acceleration and hill climbing are known to be acceptable (since people keep using them) and the power input is known (200-300W from memory).

So your solution is in the right ball park, now it comes down to details of gear ratios, power bands, efficiencies, weights etc.

It might turn out to be more efficient to leave the electric bits off and just use the IC motor.

Go check out this CR-4 thread from earlier this month. Many similarities in that project to yours. You will find useful numerical info there.

vehicle power calculation 01/17/2010 3:09 AM

http://cr4.globalspec.com/thread/49269#newcomments

Ed Weldon

Some of the numbers seem out of proportion here. One HP = 0.746 KW, so a 1 KW (1.34 HP) generator would be about right for a 1 HP motor, allowing some reserve.

However, why have a motor at all? Just let the engine drive the bike mechanically, saving the weight of the motor and one step of efficiency loss.

No battery has been mentioned so far, so I'm not sure this can be called a genuine hybrid. The idea of a hybrid is that much of the time vehicle does not need the full rated HP, so the generator can be a bit more than the average HP required. When passing or going uphill, the battery supplements the generator to give full HP. When going flat or downhill, the generator has more capacity than needed, so it recharges the battery.

If the generator is 0.8 KW, and there is a battery, this should be about right for a 1 HP motor. To size the battery, you need to estimate a worst-case hill or headwind, how much extra energy that will require above the generator capacity, and then convert to amp-hours needed for the battery.

Some things you must do yourself:

-- Decide upon the performance required. Hill climbing speed, payload, maximum speed on level ground, tire type and their rolling resistance, etc.

-- Decide upon energy management strategy: parallel hybrid, series hybrid, plug-in hybrid?

-- Based upon desired performance, what sort of body and therefore what sort of aero Cd and what frontal area will the car have?

-- What overall characteristics do you want the vehicle to have, and therefore how big will it be and much will it weigh? Is there a comparable vehicle you can use for a yardstick to see if your estimates are reasonable?

Then, you can calculate the hp required to accomplish the goals of the vehicle. At that point, this post would be helpful.

Here's another.

And another.

The simple answer to your question is that almost any motor can move almost any vehicle... it's just a matter of how fast, at what rate of acceleration, and/or up what grade. (A small electric-motor-assisted hand truck can be used to move a very large airplane... on a level surface and at very low speed.)

The motor driving the wheels must be able to supply the peak hp requirement for the anticipated most difficult condition (e.g. going up a 20% grade hill for 2 minutes, etc). The generator must be able to supply the averaged, long term hp requirement, assuming you are using a battery bank to store energy when the vehicle is using low power (as in cruising at medium speed). To determine that ratio of average to peak, you have to look at the anticipated driving cycle: certainly, if the vehicle goes very slowly on the level most of the time, and rarely has a burst to top speed for an instant, then the ratio of average to peak could be low. If the vehicle operates at top speed all the time, then the ratio would have to be 1:1 (plus some for losses) -- in which case, hybridization would not make sense. (For this reason, you are unlikely to see hybrid airplanes.)