i got to thinking the other day and what if VEX somehow developed an alternator system much like a car has. With a car, it does not run purely on the battery, it uses the alternator to charge it thats why it lasts a few years and i think if VEX made an alternator for our robots, our batteries would not die quite as much and wont suddenly die while we are in a match. just an idea. let me know what you all think 
Where will we mount (on the robot) our internal combustion engines that we will use to turn our alternators and thereby convert stored chemical energy (presumably stored in hydrocarbon fuels) into mechanical energy into electrical energy into stored chemical energy (stored in the battery chemicals)? 
Blake
I can see where you are coming from, but this is starting to sound a bit like perpetual energy.:o
Unfortunately, the amount of energy in the universe is a constant. So, if you put some amount of energy into something, you canāt get more out. What the car is doing is converting energy from gasoline into electricity. On the bots, the power is already in batteries stored as electricity. If we ran a motor than spun an alternator that recharged the battery, then factor in the inefficiencies of the system, we would end up with less energy. So, you end up wasting battery power.
Believe me, hundreds of people have tried systems like this. Look up āBedini Motorā and see how people fail to make it work - and a lot of hoaxes claiming they got it to work.
im talking about making a chain driven one that would get power from the wheels as the robot drives. an alternator does not convert gasoline into electricity, it simply takes the power the motor produces and uses a belt to spin a metal wired coil around a magnet to create electricity that runs back into the battery. its a very real idea, it might cost a pretty penny for the robots but i think it would be worth it
But you have to remember that the energy powering the wheels is coming from the motors which get energy from the battery, which would create an endless cycle by what you are suggesting.
An alternator is essentially a generator. A generator converts mechanical energy into electrical energy. therefore, it is impossible to gain energy in this scenario, because there is no new source od energy other than the main robot battery.
i never said that the robot will have to run forever on one charge, that would just be ludicrous, but it would be nice to put some of the power exerted into the robot and have it partially recharge the battery
But it wouldnāt even partially recharge the batteryā¦
Turning the coil in the generator would require energy (ever try spinning a VEX motor?), which would drain the battery fasterā¦
i think there is a way to do it. im not quite sure how but where theres a will, theres a way
the reason that this wouldnāt work quite the way i think you want it to is because an alternator requires a decent amount of torque in order for it to spin when it is charging batteries. Therefore if you were to add an alternator to your robot you would also have to add more motors to your drive to compensate and in the end you are fighting an impossible battle. An alternator isnāt really anything more than a motor that is being spun rather than doing the spinning.
One of my favorite little cartoons that relates to this was a little drawing that my engineering teacher drew on the board and it was a man on a sailboat blowing into the sailboats sailā¦ just think about it and how it relates.
If it were possible to us an alternator the way described in the OP every robot on earth would have oneā¦ or ten on them.
~DK
Well, there are those systems in hybrid cars that generate electricity from the wheels. They only run while the car is braking, slowing the car down faster, and recovering some of the energy. Unfortunately, Vex doesnāt have brakes, it just stops on the resistance from the motor and friction.
If i am not mistaken when the robot is rolling forward as you described (no motor power just coasting forward due to momentum) you are actually using the motors as generators. I mean we have all manually pushed down our robot arm when the motors are plugged in and seen how the micro-controller lights light up, i am not sure about the wiring inside of the micro-controller but it is possible that we are actually charging our batteries a bit when we coast to a stop.
I donāt know exactly how many FIRSTers there are here but my team joked around this year about our mini-bot charging up a bit every time it coasted down the pole after the off switch was triggered at the top of the pole.
~DK
Instead of using a combustion engine, I would use a pneumatic āmotorā made from pistons to power a generator. Or, you could just plug the batteries into the chargerā¦
Realistically though, does anyone know how much voltage a motor actually generates when the robot is ācoastingā to a halt? And is it even possible to charge the battery like that? Itās very impractical, but itād be interesting to know.
Now that i think about it a bit the voltage generated has to be less than the voltage that is fed to the motors to drive it up to the speed that it is stopping from (I am pretty sure) and this would mean that it would not be greater than the battery voltage so it wouldnāt charge itā¦ (I think)
~DK
The reason that the alternator would not work is simple.
Lets visualize the following scenario.
You have 1 motor hooked to the battery and 1 alternator (which is essentially another motor) hooked to the motor.
Lets say that just by free spinning the motor you use 1 Watt; Now you have taken 1 watt away from your battery. If you want your Watt back in the battery you need to charge it. So lets use the alternator to charge it.
If the alternator was perfect you would need to put 1 watt in Horse power which is 0.0013HP to the alternator for it to produce 1 watt in electrical energy Remember 100% efficiency means ( Pin = Pout )
So Now you need to put 1 watt into the alternator so it can produce 1 watt but the motor takes 1 watt just to rotate.
And you end up using 1 watt just to move the motor and 1 watt to get 1 watt out of the alternator.
What happened? you use 2 watts and you get 1.
That was the long way of explaining it.
The short way is, (You can never get more energy out of something than the energy you put in. )
For an alternator to produce 1 watt, you need to feed it 1 watt + the losses from the conversion of mechanical energy into electrical.
In a real world an alternator can be up to 60% efficient so if you want 1 watt you will need to feed it 1.66 Watts.
And that, Iām afraid, is where you are mistaken.
(In the presumed automotive scenario) Hydrocarbons are the internal combustion engineās fuel, and that engine is the prime mover for the mechanical systems that are linked to the alternator and that consequently cause the alternator to turn.
An automobileās alternator doesnāt spin just because it is feeling whimsical and wants to get dizzy :). Something has to make it move, and that something requires an energy input in order to be able to produce the energy output that becomes the reason the alternator core is spun.
Blake
Thats one way to say it but Literally the alternator converts Mechanical energy into Electrical energy.
The combustion engine is the one converting from Hydrocarbons to Mechanical energy.
In the car is a three step process. but looking only at the alternator is a two step process.
Hmmm, That sounds like what I read in Post # 2 of this thread.
Post #2 appears to be more pedantic than post #15; and #15 appears to have been written to drive home the big picture that #2 describes in more detail.
Without expanding āthe system of interestā to include ancient dinosaurs and the rest of the universe; it is sensible to say that chemical energy extracted from gasoline is used to (re)charge a typical automobileās battery.
Blake
Yes, but the point I am trying to make is that you donāt necessarily need the chemical energy from gasoline, you just need mechanical energy for the alternator to work, so you could power your alternator from an electric motor or a wind turbine
Yes, but the point Im trying to make is that you dont necessarily need gasoline to power your alternator, you could power it from an electric motor or a wind turbine
that is EXACTLY what im trying to say