So I was checking out a Toyota Prius hybrid car, and the salesman told me that it recharged the battery whenever the car’s breaks were applied, hence never needed recharging like a pure electric car does.
That raised the question, why not recharge the battery like regular cars do, using the energy from the gas engine via a belt? Seems this would allow frequent recharging and maybe up the mileage. Is there some technical reason this is unfeasible? The salesman for the record, did not know.
The Prius can do that.
It just also uses the normally wasted braking energy to recharge the battery.
You’re going to take an efficiency loss to use engine power to charge a battery. There’s no way you get the more, or even the same amount of energy out of the system. So yeah, you could charge the battery off the engine, but it would result in less power ultimately making it to the wheels. Gas powered cars charge their batteries simply because they need a charged battery to run the starter and the accessories when the engine isn’t running. It wouldn’t be a way to add efficiency to the drivetrain.
Charging while braking is essentially free energy - that energy is going to waste, so you might as well recapture it.
the salesman was an idiot (but I repeat myself.) Most/all hybrids recharge the traction battery by regenerative braking and/or having the gas engine spin the motor/generator. Pure electric cars need to be plugged in simply because they have no gas engine to spin any generator.
Charging when you brake is called regenerative braking. The Prius also charges its big battery from running the engine, although it uses the electric motor as a generator and transfers that motion through the transmission instead of through a belt driven alternator. Regenerative braking does a lot more of the charging IME.
yes, he said it used regenerative braking, but why do it that way when using the gas engine power would also do the trick and I imagine deliver a lot more energy? I mean, I know there will be some power loss to recharge, but possibly a negligible one. Do 12 V batteries use up a lot of engine power?
What’s the benefit you’re thinking it would provide?
There are plug-in hybrids that have a small gas engine to recharge the battery. But it’s a measure to increase range, not efficiency. If you already have an engine driving the wheels directly, then using that engine energy to charge the battery and then using the battery to power the wheels is going to be less efficient. There’s one more step in there to lose energy.
The appeal of regenerative braking is that the energy is going to waste anyway. But having the engine charge the battery (which makes the engine work harder than simply driving the wheels) ultimately gets you less power to the wheels for the same amount of gas.
The Prius does do this. It uses the internal combustion engine at appropriate times to charge the batteries. It does this as well as using regenerative braking.
IT DOES BOTH!!!
look, conventional braking is nothing more than wasted energy. You push the pedal, the calipers press the pads against the rotors, and everything gets hot as the brake components dissipate the car’s kinetic energy as heat. And that heat doesn’t do any other useful work. Hybrids and EVs will switch the electric drive motor into generator mode when you press the brake pedal to try to recover as much of that energy as possible.
And that’s the key. the electric motor that hybrid cars use can also be a generator. So, hybrids also will fire up the gas engine to spin the motor as a generator when the traction battery needs recharging, and there’s no braking or coasting to try to recover energy from.
What? I don’t think you even know what question you’re asking. The battery that supplies the Prius’s electric drive motor is about 300 volts. it does also have a conventional 12 volt battery but that’s tied to the 12 volt accessory system. it has nothing to do with moving the car.
The OP is making a classic mistake.
The energy that the engine uses to recharge the car’s battery is not free. In fact, it’s rather inefficient - if you used all the engine’s power to recharge a battery, and then ran an electric motor off of the battery, it would be less efficient than just running the car directly from the engine.
So, the Prius tries to recharge it’s Hybrid battery from wasted energy as much as possible - it only uses the engine to recharge it if it absolutely has to.
the OP seems to think “hybrid” is a magic bullet, given the thread OP has posted in IMHO.
OP doesn’t seem to realize that batteries are a storage medium; they can’t create energy.
I think the mistake is actually that he thinks well, the engine is already spinning, might as well attach a belt to it and capture some of that energy. Not realizing that the engine will have to work harder to keep up with the increased load.
You could use a gas engine to charge batteries, then run electric motors from them.
But it would be more efficient to leave the batteries out of that scenario.
I don’t think the OP is falling into the “free energy” trap, but that he’s listening to a clueless salesman. there’s a disconnect in that the “battery” in a conventional car has a limited role. it’s there to start the car, and be a reserve in case the alternator fails. Otherwise, during normal operation, the alternator supplies all of the electrical power the car needs (which it gets by conversion of the mechanical power from the engine.) Hybrids have two batteries of interest; the “storage” battery which is the bog-standard lead-acid 12V battery which is tied to the accessories, and the ~300V traction battery which supplies the propulsion motor. When you drive a hybrid, if you’re running on EV power you’re drawing from the ~300V battery, and when braking, the motor/generator recharges the ~300V battery.
No, it’s not negligible. It’s enormous.
Is there a science or technology museum near you? If so, see if they have a hand-cranked generator exhibit. If you crank the generator with no load attached, so it’s not doing anything but generating a voltage but not driving a current, it’s very easy to turn - all you’re doing is overcoming the inertia of the rotor. Then you put a load across the generator - usually a light bulb so you can see what’s going on. It immediately becomes MUCH more difficult to turn the generator. Keeping a 100W bulb fully lit is damn near impossible for more than few seconds. And that’s what a gasoline engine needs to do to charge batteries in a hybrid. They have to generate the same amount of energy as the batteries will be called on to provide - more actually, due to losses.
Clearly the salesman didn’t explain that regenerative braking is free energy (figuratively). In regular cars that energy is lost in the braking process. When the batteries are recharged from the gasoline engine it’s an inefficient process and should be minimized.
The energy to charge the main batteries can’t be negligible. Those batteries are substantial enough to be able to propel a car. To recharge them in real-time, then, you need to use the full output of an engine that’s substantial enough to be able to propel a car. If it were negligible to charge the batteries, then you’d also only be able to get a negligible amount of energy out of them.
The Prius has a generator in the “backside” of its transmission. This generator adjusts its load on the transmission’s “back-force” to effect a real continuously variable transmission, so that the ICE can operate at optimal efficiency (and does not have to be as big). The power out of that generator either goes into the battery or into an electric motor that can provide additional power to the drivetrain (or can be the primary power source). The Prius battery (the big one) is kept half-full so that there is a place to put the braking or back-force electricity is the electric motor is not taking all of it. A few people who live in the city have modified their Prii to operate as an electric plug-in for short trips, but the electric range is necessarily limited by the fact that you just cannot fill the battery to the top because it needs to be used to catch excess juice.
They actually do make “serial hybrid” vehicles, where the motor runs a generator that drives the wheels. One example of this is the Chevy Volt, which can run in pure battery power or can use its ICE to generate electricity to run the electric motor. The primary advantages to serial hybrids are that the ICE can run most of the time at an optimal speed, braking energy can be put into the battery, and battery power can be held in reserve to even the load on the ICE when more power is needed. A serial ICE can be considerably smaller than the same powerplant if it were driving the wheels. But if you have never seen a Volt (I do not know of having seen one), you almost certainly have seen another serial hybrid pulling freight down the rails.
I have a hybrid Camry. If the gas engine is part of the drive train, why would it ever absolutely have to charge the batteries from the gas engine? I don’t know anything about the batteries that are used–do they have to be kept at a minimum level of charge, regardless of whether they’re needed to propel the car?