Explaning ESS to a middle schooler

[Fudster]

You’re overthinking it. ESS is simply one of the many ways that auto manufacturers use to meet the government’s near impossible fuel economy standards. If not for those f/e standards, ESS would not exist in any vehicle. There’s no real benefit to the consumer.

Maybe...like you I'd certainly not trust the manufacturer to do right by me, but the SAE has found such systems to save gasoline... https://www.roadandtrack.com/new-ca...303/automatic-start-stop-useful-fuel-savings/

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[mwilk012]

.but that higher efficiency battery is charged by a low efficiency engine. That battery can't really shine if its power is derived from a poor power energy conversion mechanism right? (i.e. the engine, which takes the chemical energy of fossil fuels and converts it to mechanical energy , which is converted to electrical energy in the alternator, which is converted to chemical energy in the battery.)

The additional energy used by the alternator and therefore the engine to recharge the batteries is very small, compared to the engine not operating at all.

 

[J0E]

You are forgetting a major component and that is the AUX battery which has a very short lifespan. They can start failing as early as 2 years and if you've got the original one still at 4 you are an enigma.
So you need to factor in how much gas you are really saving for the year. It's pretty pathetic I'm guessing and then factor that against the cost of the AUX battery which resides in your Jeep to power that $hitty ESS system. This is real life, something the dip$hit ECO morons don't consider.
Everything looks wonderful and all warm fuzzies on paper but in real life there is always a trade off.

That's the problem with CAFE standards, they don't look at the whole picture. Most consumers need to pay a shop to replace the ESS motorcycle battery. Theirs's a carbon footprint for every dollar. The ESS system is a net loser in carbon footprint when you look at the whole system.

ESS is also about emissions.

And people on this forum could argue forever about if the emissions from gasoline are better/worse than battery production.

It's 99% about fuel efficiency. The emissions from replacing the ESS battery far outweigh the savings from ESS.

I actually love the ESS since it never goes on in my climate (low to mid 80's). But it's trained me to use MSS (manual stop start) on the trail. We often stop to pick a line and I always use MSS, the rest of the folks keep their engine running. I do save save fuel.

You’re overthinking it. ESS is simply one of the many ways that auto manufacturers use to meet the government’s near impossible fuel economy standards. If not for those f/e standards, ESS would not exist in any vehicle.

Exactly

There’s no real benefit to the consumer.

But there is a real downside.

 

[YJdude]

Holy shit... This JLForum became JLMC²Forum overnight! Seriously.. there are some very intelligent folks here.
ASS is the dumbest thing ever in a Jeep, PERIOD. It's like bringing toilet paper scuba diving.
I disabled mine on day one.
Sadly, to truly explain ASS things would get political.

 

[bigfoot21075]

The alternator does not get harder to turn because of an increased load. The Kinetic Forces do not change. The wires may be hotter but that is it.

 

[Mikester86]

Not to mention there is nothing keeping the oil at the top of the engine. ESS is dumb!

 

[Fudster]

The alternator does not get harder to turn because of an increased load. The Kinetic Forces do not change. The wires may be hotter but that is it.

Robert, I'd tend to agree with your assessment as it relates to earlier model vehicles on the road today. But the JL, and many other vehicles today incorporate the use of a smart alternator which allows the alternator to produce varying electrical loads based on demand, in turn reducing mechanical load on the engine in times of such lower electrical demand by vehicle appliances and batteries.

 

[bigfoot21075]

Robert, I'd tend to agree with your assessment as it relates to earlier model vehicles on the road today. But the JL, and many other vehicles today incorporate the use of a smart alternator which allows the alternator to produce varying electrical loads based on demand, in turn reducing mechanical load on the engine in times of such lower electrical demand by vehicle appliances and batteries.

FUDSTER!!! Thanks for the education my friend. I appreciate your post. Even an old guy like me can learn ? I am a hot rod/classic car nut, but I have to say it could be argued that RIGHT NOW may in fact be the golden years of the automobile......

 

[keeperman13]

If I were explaining it to a middle schooler, I would start by calling it auto start stop (ASS) and go from there.

Bingo, gotta get them invested first!

 

[driventoadventure]

One thing that I haven't yet seen regarding the charging efficiency etc, is that the engine produces WAY more power than the vehicle consumes - the only exceptions being when accelerating or climbing hills etc (basically all forms of acceleration.) This is where ESS comes in.

During the vehicle's least efficient periods (when it is stopped and idle) it uses a battery and electric motors (which are several multiples more efficient) to drive the few things (including AC on vehicles with electrified AC and heating on vehicles with electrified heating) that are still needed. Modern vehicles are able to start fast enough, that anyone who is paying attention can get the engine restarted and running before they need the power to accelerate, then when you are cruising to the next light or driving down the highway and your vehicle is using very little of its power, it uses some of the spare power (since it has a minimum amount of power per RPM, and those RPMs are speed fixed by your transmission) to recharge the efficient battery it was discharging.

This is the same principle behind why modern vehicles are using gearboxes with more and more gears, and the same principle behind hybrid vehicles. This is also the same reason why Hybrids are SO MUCH more efficient in city usage than they are in highway usage. It is why on highway usage, hybrids are only mildly more (if not less depending on weight/power, aerodynamic, charge-vs-dicharge profile, etc) efficient than gasoline engines - because when properly geared and the power is properly distributed, you are wasting and/or using less power being converted to acceleration. You are also more efficiently using the power that is already being converted to heat.

To those people are talking about the generator drawing power, while it is true that mechanical energy is harvested, the load that is putting on the engine is so insignificant compared to the change in its thermal energy (at least in any of these Jeep engines) that the power 'loss' is nonzero (I am using the mathematical term here for being so uncountable that it is basically zero, but it does exist.) You can't forget that the mechanical output of your engine is not only small compared to its actual generation, but that to a certain point, your engine is actually producing more mechanical energy per joule as its conversion mechanism (the pistons/rods/etc) gets loaded.

 

[Heimkehr]

How hard would it be to have the ESS system removed from your Jeep Wrangler...

Disabling ESS electronically is dead simple. Install an eliminator harness, or purchase a Tazer and activate the related functionality.

As for removing the small battery, there are separate instructional threads on the matter.

 

[Fudster]

One thing that I haven't yet seen regarding the charging efficiency etc, is that the engine produces WAY more power than the vehicle consumes - the only exceptions being when accelerating or climbing hills etc (basically all forms of acceleration.) This is where ESS comes in.

During the vehicle's least efficient periods (when it is stopped and idle) it uses a battery and electric motors (which are several multiples more efficient) to drive the few things (including AC on vehicles with electrified AC and heating on vehicles with electrified heating) that are still needed. Modern vehicles are able to start fast enough, that anyone who is paying attention can get the engine restarted and running before they need the power to accelerate, then when you are cruising to the next light or driving down the highway and your vehicle is using very little of its power, it uses some of the spare power (since it has a minimum amount of power per RPM, and those RPMs are speed fixed by your transmission) to recharge the efficient battery it was discharging.

This is the same principle behind why modern vehicles are using gearboxes with more and more gears, and the same principle behind hybrid vehicles. This is also the same reason why Hybrids are SO MUCH more efficient in city usage than they are in highway usage. It is why on highway usage, hybrids are only mildly more (if not less depending on weight/power, aerodynamic, charge-vs-dicharge profile, etc) efficient than gasoline engines - because when properly geared and the power is properly distributed, you are wasting and/or using less power being converted to acceleration. You are also more efficiently using the power that is already being converted to heat.

To those people are talking about the generator drawing power, while it is true that mechanical energy is harvested, the load that is putting on the engine is so insignificant compared to the change in its thermal energy (at least in any of these Jeep engines) that the power 'loss' is nonzero (I am using the mathematical term here for being so uncountable that it is basically zero, but it does exist.) You can't forget that the mechanical output of your engine is not only small compared to its actual generation, but that to a certain point, your engine is actually producing more mechanical energy per joule as its conversion mechanism (the pistons/rods/etc) gets loaded.

Excellent!

Now to boil it down to that a 6th grader understands. I'm going to try, anticipating in hypothetical, and I hope you correct me where needed:

"Son (my 6th grader), in order to not only get the vehicle going, but going faster, it needs to have a relatively large power plant that applies stored energy to the wheels. Most commonly this involves the combustion of fossil fuels to turn the chemical energy stored in this liquid fuel's chemical bonds into mechanical energy.

But once going, keeping the vehicle at a reasonable speed, particularly when not on inclines, is a far, far less energy intensive process due to Newton's first of law of thermodynamics: which states that a body in motion at a constant velocity will remain in motion in a straight line unless acted upon by an outside force.

(If I'm asked why Newton's 1st law is true--I'm afraid I'm going with Tom's @40Caliber "it is what it is" explanation.)

Of course in the real world there's plenty of those "outside forces." There's friction, and energy lost to sound, for example, which is why keeping the vehicle going at a constant speed on a flat road still requires fuel and the vehicle won't run forever without a visit to the gas pump. But keeping a vehicle going 30 mph on a flat surface, once at 30 mph, requires so little of the power plant that some of that power plant's capacity can be used for other things, like charging batteries used to keep appliances on when the engine isn't needed at all, like when stopped at traffic lights."

Son: "but rather than ESS couldn't the engine by taxed less when running the same speed on flat road?"

Me:"It is. Not only does the engine run slower, but more and more of this excess energy capacity needed to accelerate the vehicle is being captured and preserved in modern vehicles in more efficient gearing systems, hybrid vehicles and regenerative braking systems where the vehicle's energy in motion (kinetic) rather than converted completely into the heat and sound of brakes, faces in part the friction/resistance of generators that turn/store this energy back into the chemical bonds stored in batteries. You have to build a lot of capacity into the engine, much of which often isn't needed, where it can be somewhat saved in reduced idle, and somewhat tapped for battery storage."

 

[entropy]

The small battery costs about $120~$150 depending what you end up buying aftermarket. This system also taxes the big battery because they are connected in parallel and the small battery has a huge resistance, like 10 ohm. The big battery costs anywhere between $200~$400 depending what brand you get.

If you use your Jeep for off-roading as it is intended to be used and tax the electrical system with a high volume compressor + winching things your batteries wont last. Ask me how I know. And you'll have to deal with reliability issues constantly "ESS not ready battery charging", "Battery protection mode" etc...

You will never recover the pennies saved from ESS or your mental health lost to the issues the system causes. My 2020 Camry does not have ESS. Toyota knows it is just something else that can go wrong.

ESS is not about saving the consumer money. It is about emissions at a large scale. About the thousands of wranglers stopped in traffic in Los Angeles.

After 3 years of dealing with it. I bypassed my aux and disabled ESS. I have 0 issues since then and my Aux battery can be used to start the jeep in case of an emergency

 

[driventoadventure]

Excellent!

Now to boil it down to that a 6th grader understands. I'm going to try, anticipating in hypothetical, and I hope you correct me where needed:

"Son (my 6th grader), in order to not only get the vehicle going, but going faster, it needs to have a relatively large power plant that applies stored energy to the wheels. Most commonly this involves the combustion of fossil fuels to turn the chemical energy stored in this liquid fuel's chemical bonds into mechanical energy.

But once going, keeping the vehicle at a reasonable speed, particularly when not on inclines, is a far, far less energy intensive process due to Newton's first of law of thermodynamics: which states that a body in motion at a constant velocity will remain in motion in a straight line unless acted upon by an outside force.

(If I'm asked why Newton's 1st law is true--I'm afraid I'm going with Tom's @40Caliber "it is what it is" explanation.)

Of course in the real world there's plenty of those "outside forces." There's friction, and energy lost to sound, for example, which is why keeping the vehicle going at a constant speed on a flat road still requires fuel and the vehicle won't run forever without a visit to the gas pump. But keeping a vehicle going 30 mph on a flat surface, once at 30 mph, requires so little of the power plant that some of that power plant's capacity can be used for other things, like charging batteries used to keep appliances on when the engine isn't needed at all, like when stopped at traffic lights."

Son: "but rather than ESS couldn't the engine by taxed less when running the same speed on flat road?"

Me:"It is. Not only does the engine run slower, but more and more of this excess energy capacity needed to accelerate the vehicle is being captured and preserved in modern vehicles in more efficient gearing systems, hybrid vehicles and regenerative braking systems where the vehicle's energy in motion (kinetic) rather than converted completely into the heat and sound of brakes, faces in part the friction/resistance of generators that turn/store this energy back into the chemical bonds stored in batteries. You have to build a lot of capacity into the engine, much of which often isn't needed, where it can be somewhat saved in reduced idle, and somewhat tapped for battery storage."

That is pretty good way to simplify it where your child can ask more if they want to and understand if they do not want to.

A nitpick that can help you refine your model and thought (and this doesn't NEED to be elaborated on unless someone wants to dive much further in): your vehicle is turning chemical energy into thermal energy, and the generation of that thermal energy is what is creating the mechanical energy. This is part of why your vehicle has power bands - (what follows is at a very, VERY basic level) at certain speeds, there is not enough time (too much time from slower speeds is a different issue all together) for that energy to fully transfer (in the case of ICE mainly through expansion). In the case of steady-state cruising, your are much closer to the rpm at which that energy transfers most efficiently, and back to my previous comment, the difference in potential is small enough that its overall effect can be negligible. The caveat to that being that the alternators on these vehicles are very small compared to the energy potential of these engines.

For what it is worth, there are many nuances that vary from power-train to power-train, and I am trying to reference the core physics behind the process. The principle remains the same and is why a properly utilized and designed ESS is quite measurably beneficial not only from a fuel economy but from a pollution perspective, but just like in (ex) Economics there is a human element which adds an impossible-to-quantify variable to the equation.

(edit) PS: If your child doesn't accept the very apt "It is what it is" you can also point out that energy can't be created or destroyed, that is why Inertia behaves as it does. Once you put energy into a system, it doesn't just disappear.

 

[kah.mun.rah]

I would tell a middle schooler,

“When you get older be careful who you vote for or your car will continue to have useless design features to satisfy political regulations. In the meantime, be a pal and press that button for me that looks like the Avenger’s logo…”

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