EV (electric vehicle) News and Discussion

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#1956133 13-Feb-2018 09:01

MikeAqua:

For something like a light urban delivery truck - perfect and will reduce air pollution too. A guy I know in Nelson just bought one for his dry cleaning business. He is doing minimal km and carrying a very light load too.

Range is still an issue for trucks outside city areas. For moving stock or logs or line hauling freight on state highways - forget it. Or you would require swap-out battery units or just swapping traction units (like formula-e).

Trucking companies tend to work their trucks hard, because margins are low so you need volume. A single truck driver is allowed to drive for up to 13 hours in a day - and many do. That equates to a daily range of something like 900km, with GCM of up to 50 Tonnes. Then you need to consider additional power for secondary plant like refrigeration.

BTW addressing grade by improving highways would help by removing some of the heavy braking burden.

If you are serious about reducing trucking pollution, there are pre-existing solutions already in place in N.Z. Rail freight (which will soon be de-electrified :-( ) and sea freight. It costs more to truck freight from Wellington to Piction than ship it from Auckland to Christchurch - capacity is the constraining issue. The sea freight companies got very busy (>100% capacity) during the Kiakora SH1 outage as people realised there has actually a cheaper option that was unaffected by the land-slides. The problem is that most peoples vision is only as wide as their wind-screens.

MikeAqua

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#1956134 13-Feb-2018 09:04

Aredwood:

Actually braking is not a problem for EVs - even large and heavy ones like semi trucks. Due to regenerative braking.

Are you sure about that. Could a 40 - 50 tonne truck going down a hill brake on re-gen alone? That is a lot of enrgey to dissipate.

Or would service brakes be required as well?

A diesel truck would use different combinations of gearing (engine braking), exhaust brakes and service brakes to manage descent down a steep hill.

I've seen articles about EV mining trucks going downhill full and uphill empty have net positive energy generation. But that's a special and very favourable case. Most trucks are going up and down the same hill with more or less the same load.

It's an interesting area

Mike

MikeAqua

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#1956137 13-Feb-2018 09:11

happyfunball:

It will be years until we see it here, but the Tesla semi (version 1.0) claims 500 mile range and 400 miles in 30 minutes of charging. Factor in lower maintenance costs, lower fuel costs, and you have more profitable truck.

With what load though? And in what conditions?

Tesla are talking about the same load capacity as a diesel semi. I can sort of believe that because they save weight with motors vs an engine and then lose weight due to the batteries.

A semi in the US is limited to 36,000kg gross vehicle mass (vehicle + load). Compare that to 50,000kg for 50Max HPMV

A semi is also a limiting format ... there are applications in NZ where a rigid body truck with a full trailer or a B train are better configurations.

Mike

tripper1000

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#1956162 13-Feb-2018 09:21

MikeAqua:

Are you sure about that. Could a 40 - 50 tonne truck going down a hill brake on re-gen alone? That is a lot of enrgey to dissipate.

It the engine and battery can overcome gravity and get the truck up the hill, then logically the engine and battery can overcome gravity and get the truck down the hill - particularly if you come down at the same speed you go up. If you come down the hill at 100 Mph and expect the regen to suddenly pull you up, that isn't going to happen no matter weather you are talking diesel or EV.

Electric trains have been doing regen braking and dissipating huge amounts of energy for years, although admittedly they are usually not putting the regen into batteries.

MikeAqua

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#1956185 13-Feb-2018 10:19

tripper1000:

It the engine and battery can overcome gravity and get the truck up the hill, then logically the engine and battery can overcome gravity and get the truck down the hill - particularly if you come down at the same speed you go up. If you come down the hill at 100 Mph and expect the regen to suddenly pull you up, that isn't going to happen no matter weather you are talking diesel or EV.

I'm not sure that stacks up ...

In an EV Going uphill the battery is sending electricity to the motor. Battery energy is used both to overcome the mass and friction inherent in the drive system and also to prevent or limit deceleration due to gravity.

Going down hill regen braking uses the mass and friction of the drive system to prevent or limit acceleration due to gravity. The battery is now passive. It can't make the drive system harder to turn without using energy to do so - i.e. active braking.

Mike

tdgeek

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#1956196 13-Feb-2018 10:40

tripper1000:

MikeAqua:

For something like a light urban delivery truck - perfect and will reduce air pollution too. A guy I know in Nelson just bought one for his dry cleaning business. He is doing minimal km and carrying a very light load too.

Range is still an issue for trucks outside city areas. For moving stock or logs or line hauling freight on state highways - forget it. Or you would require swap-out battery units or just swapping traction units (like formula-e).

Trucking companies tend to work their trucks hard, because margins are low so you need volume. A single truck driver is allowed to drive for up to 13 hours in a day - and many do. That equates to a daily range of something like 900km, with GCM of up to 50 Tonnes. Then you need to consider additional power for secondary plant like refrigeration.

BTW addressing grade by improving highways would help by removing some of the heavy braking burden.

If you are serious about reducing trucking pollution, there are pre-existing solutions already in place in N.Z. Rail freight (which will soon be de-electrified :-( ) and sea freight. It costs more to truck freight from Wellington to Piction than ship it from Auckland to Christchurch - capacity is the constraining issue. The sea freight companies got very busy (>100% capacity) during the Kiakora SH1 outage as people realised there has actually a cheaper option that was unaffected by the land-slides. The problem is that most peoples vision is only as wide as their wind-screens.

If shipping is cheaper, why doesnt a company pursue that? That would also mean trucks can be more short haul and then have a better viability for EV

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wellygary

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#1956198 13-Feb-2018 10:43

tdgeek:

If shipping is cheaper, why doesnt a company pursue that?

Because it is generally slower,

tdgeek

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#1956207 13-Feb-2018 10:55

wellygary:

tdgeek:

If shipping is cheaper, why doesnt a company pursue that?

Because it is generally slower,

I think its about 24 hours CH-AK going by past horse float days. Add in weather, etc. If the companies are used to and like a 24 hour shipment, what would they do if trucking was not an option? They would get used to 72 hours. If it was 8 hours to AK and a truck takes 24, they will say thats too long, they need to smarten up and adapt. If we had a good shipping service, which is cheaper, and it uses less FF, and allows EV trucks to be viable, that seems the way forward. What Im used to isnt always the best option

Aredwood

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#1956267 13-Feb-2018 11:39

MikeAqua:
tripper1000:

It the engine and battery can overcome gravity and get the truck up the hill, then logically the engine and battery can overcome gravity and get the truck down the hill - particularly if you come down at the same speed you go up. If you come down the hill at 100 Mph and expect the regen to suddenly pull you up, that isn't going to happen no matter weather you are talking diesel or EV.

I'm not sure that stacks up ...

In an EV Going uphill the battery is sending electricity to the motor. Battery energy is used both to overcome the mass and friction inherent in the drive system and also to prevent or limit deceleration due to gravity.

Going down hill regen braking uses the mass and friction of the drive system to prevent or limit acceleration due to gravity. The battery is now passive. It can't make the drive system harder to turn without using energy to do so - i.e. active braking.

It depends on how much power the battery can absorb while charging. Look at the claimed recharge rates listed for EV trucks and buses. That is some serious regen braking. And having very active regen braking is also an easy way to increase range without needing to also increase battery capacity.

Of course if you don't mind wasting that power. You just dump it via a large resistor bank. (heating elements)

It also makes sense from a safety point of view. If the service brakes are only needed for an emergency stop.

happyfunball

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#1956276 13-Feb-2018 11:55

MikeAqua:

Going down hill regen braking uses the mass and friction of the drive system to prevent or limit acceleration due to gravity. The battery is now passive. It can't make the drive system harder to turn without using energy to do so - i.e. active braking.

If you turn an electric motor, it will generate electricity. The more you draw electricity from it (to put into the battery, or wherever) the harder it becomes to turn the motor. EV cars experience much less brake wear if they employ regeneration, as would EV trucks.

An alternator in a combustion engine works exactly the same way, the more electrical load there is in the system, from charging the 12v battery or elsewhere, the harder it is to turn the alternator, using more fuel.

tripper1000

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#1956313 13-Feb-2018 13:00

MikeAqua:

I'm not sure that stacks up ...

In an EV Going uphill the battery is sending electricity to the motor. Battery energy is used both to overcome the mass and friction inherent in the drive system and also to prevent or limit deceleration due to gravity.

Going down hill regen braking uses the mass and friction of the drive system to prevent or limit acceleration due to gravity. The battery is now passive. It can't make the drive system harder to turn without using energy to do so - i.e. active braking.

It sounds like you don't quite understand regen braking. The battery is not passive. Mass and friction of the drive system is not the main braking force (these are low in an EV, contributing to their efficiency) - what is, is the motor acting like a generator, and the generated electricity recharging the batteries. One of the design factors when choosing a battery for most EV's is that it can be recharged quickly - this means that the battery can easily absorb all the electricity generated by the motor in regen mode. Varying degrees of braking force is achieved by varying the amount of current feed from the motor/generator back to the battery, which enables the one-pedal system seen in the new Leaf.

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MikeAqua

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#1956335 13-Feb-2018 13:43

tripper1000:

It sounds like you don't quite understand regen braking. The battery is not passive. Mass and friction of the drive system is not the main braking force (these are low in an EV, contributing to their efficiency) - what is, is the motor acting like a generator, and the generated electricity recharging the batteries. One of the design factors when choosing a battery for most EV's is that it can be recharged quickly - this means that the battery can easily absorb all the electricity generated by the motor in regen mode. Varying degrees of braking force is achieved by varying the amount of current feed from the motor/generator back to the battery, which enables the one-pedal system seen in the new Leaf.

Still not following ...

Are you saying that the charge rate of the battery creates an additional physical force or some sort of field the generator must overcome to turn?

Mike

Linuxluver

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#1956343 13-Feb-2018 13:57

happyfunball:

Aredwood:

Then there is the contrary view - Since running an EV is far cheaper than running an ICE car, it removes alot of the incentive to take public transport instead of driving in a private car. (more-so since EVs can use some of the T2 onramp lanes). And when autonomous cars become more common, Instead of driving to work, parking at work, then driving home. You will drive to work, tell your car to drive itself home and park there, Then have your car drive itself back to your work, and pick you up again. (Double the distance per day - double the average number of cars on the roads) Or if you only need to be somewhere for a short time. You will get your car to drop you off, your car will keep on driving round the block by itself, until you are ready to be picked up again. (as paying for the electricity of fuel usage will often be cheaper than paying for parking). So in the medium to long term, it is likely that far more roading investment will be required.

As well as disrupting the business model used by Wilsons parking, and the income stream that airports make from parking.

Autonomous cars are supposed to decrease traffic because most traffic is caused by bad driving, not too many cars on the road. We could fit a lot more cars on the road if there were less hunting for parking (25% of Urban traffic is caused by people looking for parking spots), adaptive cruise control (cuts out tailgating), and many other driver errors. So even with more cars on the road, you'll get there faster. Its counter-intuitive but models show traffic will improve dramatically. Less car ownership (taxis are now much cheaper with no driver) means less cars parked on the side of the road.

Also, take away the buses (transport will be so much cheaper and no parking needed) and you'll have extra lanes.

Buses can carry 70 people in the space occupied by 3 cars....so buses won't be going away. Instead, what we might see is restrictions on the sort of silly behaviour @Aredwood (quitely right, IMHO) expects to be likely. A RUC might give people pause for thought if their car is out there circling the block all day waiting for them to go home. Emergency services will also want to be able to override direction to autnomous vehicales in the event of any emergency (pull over and get out of the way......or go somewhere outside a 5km radius of whatever location....or just go home and get off the road....or similar)

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MikeAqua

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#1956349 13-Feb-2018 14:12

Linuxluver:

Buses can carry 70 people in the space occupied by 3 cars....so buses won't be going away.

Urban EV buses should have impressive potential. 40 people are only around 3,000kg and on an urban bus there is minimal baggage.

So much room (physical and mass) for battery capacity. Minimal distance covered really, and generally low speed with lots of slowing and stopping (regen).

Supposedly we are getting some double decker EV buses in Welly. I'll be interested to see (assuming it actually happens) what routes they go on.

Mike

wellygary

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#1956355 13-Feb-2018 14:28

MikeAqua:

Supposedly we are getting some double decker EV buses in Welly. I'll be interested to see (assuming it actually happens) what routes they go on.

Tranzit's Double decker EVs will run on the Island bay-Churton Park route from July. ( they are installing an overhead fast charger at the Island bay terminus)

Going up the gorge fully loaded in a howling NWester will be interesting thou

Double Deckers in Wellington are tunnel restricted so cannot be used on the Karori-Seatoun route...

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