Which EV's charge the batteries as you brake?

Andy From Sligo

ELM327 wrote: »

+1


This idea of using a dynamo on an EV for some sort of perpetual motion comes up a lot when people new to EV ask me about it.
I generally explain it by comparing how hard you have to cycle with a dynamo up a hill compared to without one. Then you can see the lightbulb illuminate, energy isn't free.

on the one hand I can see that on the other hand you are not always driving up hills - so if one was fitted and only engaged on the straights and downhill (along with regen charging) then that resistance isnt going to be than negligible is it - the output driving the motor is going to be way way more powerful than the resistance a dynamo would present - if I were designing a system I think I would try and use the whole offering that are there to put charge back into the battery, using lightweight components as to not add extra weight to the car. So if that be dynamo + inverter + Regen braking + Solar power in the roof + yes indeed wind coming in through the front grille and into some kind of turbine generator that too.

zilog_jones

The car would be more efficient by just applying less power to the wheels, than applying more while trying recover some energy at the same time as consuming it. It's a bit pointless really. Regenerative braking is the only meaningful way of recovering energy - it's applied when you want to lose momentum anyway.

EV's don't need grilles, that would just create more drag. Again, wasting energy to generate some - always a net loss.

ELM327

Andy From Sligo wrote: »

on the one hand I can see that on the other hand you are not always driving up hills - so if one was fitted and only engaged on the straights and downhill (along with regen charging) then that resistance isnt going to be than negligible is it - the output driving the motor is going to be way way more powerful than the resistance a dynamo would present - if I were designing a system I think I would try and use the whole offering that are there to put charge back into the battery, using lightweight components as to not add extra weight to the car. So if that be dynamo + inverter + Regen braking + Solar power in the roof + yes indeed wind coming in through the front grille and into some kind of turbine generator that too.

Consider that regen has at least a 30% energy loss. I imagine energy loss from drag by fitting an air turbine etc is worse.


So let's imagine you are at a slight incline which is followed by a slight decline. It is more efficient to slow down going uphill and allow the car to speed up going down hill then to maintain the same speed throughout (this applies to fossil fuel cars too).


If you use a dynamo on the way down then you need more energy to power the dynamo/regen. So you use 100% on the flat , 120% to climb the hill and 80% on the way down. If on the way down you apply the regen then you will reduce speed quicker and need to accelerate tomaintain speed. Turning the 80% to 100%. Energy / motion/ work/force isn't "free" in an energy sense, you need to spend energy to move.

TheBoyConor

Andy From Sligo wrote: »

......
And also, do any EV's have any kind of dynamo/alternator or inverter system to charge the batteries as the car is moving ... even if its putting a trickle charge into the batteries?

That would be equivalent to trying to make a perpetual motion machine. It makes no sense and physically cannot work.

Same goes for anything like fitting wind turbine or similar devices on or about the car. These generate electrical energy, correct, but in doing so they also cause drag which saps the car's kinetic energy.

I hear these types of "why dont they......" proposals from time to time and all they do is demonstrate that the proposer lacks a fundamental understanding of the basic physics of energy and motion.

TheBoyConor

Andy From Sligo wrote: »

so , am i right in saying that the only way the batteries in the car can be topped up with charge is by means of the regen braking and then at all other times the batteries are discharging? and the motor can only be in a mode of either driving the vehicle or charging the vehicle (as in when braking) ?

So no other topping up of the batteries occur when the car is going forward and driving unless its braking?

Where is the engine on the EV, normally in the front is it? - if so , why could they not have put some kind of generator/dynamo/alternator on the back axle and through some kind of inverter to boost the charge so that as the car is driving forward it can send some kind charge to the battery even if it works out a trickle charge ?

You need to understand that putting a generator on the back wheels, or whereever, will absorb energy from the motion of the car which must be compensated for by drawing additional power from the battery.

Trying to do what you suggest and make your battery last longer would simply not work as you would be trying to defy the laws of physics - specifically the prinicple of conservation of energy.

Generators don't just spin freely and pump out power - they take force to turn. Ever plug a kettle into a generator and switch it on? - You'd notice that when you swtich it on the engine will labour heavily. This is because the electrical load the kettle draws makes the generator more difficult to turn and the engine must provide this extra effort.

mr chips

There is a German EV startup whose name escapes me which has put solar panels on a city car, but in reality this isn't very practical or cost-effective, even now after the cost of solar PV has fallen so much from where it was 8-10 years ago. Panels have to be big enough to generate a meaningful amount of power, something that the surface area of an average car just can't provide. They also need to face the sun at the correct angle to achieve maximum efficiency. If you had panels on the bonnet and roof and even the boot lid, then parked for several hours on a steep slope so that the roof is slightly more angled towards the sun, on a bright summer's day you might get 15-20 km worth of juice.

Just for comparison - my solar array at home has the same surface area as maybe six or seven large saloon cars (a unit of measurement whose recognition is long overdue ...), is ideally positioned to capture the maximum amount of sunshine throughout the day and is never shaded apart from one corner for maybe half an hour at dawn in the middle of June. Now at that time of year, if the house consumption was zero, a full day's sunshine would provide enough juice to fully charge a 24kWh Nissan Leaf, maybe even a 28kWh Ioniq, but not a 30kWh Leaf. However on the cloudiest days in the third week of December, it wouldn't provide a quarter of that.

In terms of PV, it's better to have a proper array of panels mounted on the ground or on the roof of your house, out of the shade, and have a battery which can store any surplus energy generated. This way, you'd have the option to continue meeting your domestic electricity requirements after sunset, and/or partially charge your car with "free" energy if your panels have produced more than your house needs. That's my long-term plan, anyway!

Andy From Sligo

TheBoyConor wrote: »

That would be equivalent to trying to make a perpetual motion machine. It makes no sense and physically cannot work.

Same goes for anything like fitting wind turbine or similar devices on or about the car. These generate electrical energy, correct, but in doing so they also cause drag which saps the car's kinetic energy.

I hear these types of "why dont they......" proposals from time to time and all they do is demonstrate that the proposer lacks a fundamental understanding of the basic physics of energy and motion.

well ... you cannot expect us to all be physics, mathematicians and scientists now can ye?

unkel

mr chips wrote: »

There is a German EV startup whose name escapes me which has put solar panels on a city car, but in reality this isn't very practical or cost-effective

The Sono Sion. We have a thread about it here:

Linky


As you can see from that thread, I agree with your sentiments

mr chips

Ah yeah, that's the one. The only real value I can see in the panels is (a) if you had a commute of say 6-8 miles, in which case it could suit someone without access to home or work charging so long as they could park it in direct sunlight from 9-5, meaning they wouldn't constantly have to worry about the availability of public chargers, or (b) if you were heading off on holidays and had to leave it at the airport - you park it even as it went into turtle mode and come back to a fully charged car, so long as you were taking a two-week break ...

Andy From Sligo

mr chips wrote: »

Ah yeah, that's the one. The only real value I can see in the panels is (a) if you had a commute of say 6-8 miles, in which case it could suit someone without access to home or work charging so long as they could park it in direct sunlight from 9-5, meaning they wouldn't constantly have to worry about the availability of public chargers, or (b) if you were heading off on holidays and had to leave it at the airport - you park it even as it went into turtle mode and come back to a fully charged car, so long as you were taking a two-week break ...

do Solar panels still need bright sunshine these days to work? - i thought we had come on a lot since they first were invented and that they work with any kind of daylight?

mr chips

They still work on a dull day, but they work even better on a bright day! In total, my array produces as much power as my house would use throughout the year, including most of our water heating for showers etc, and if I had an affordable way to store all of the surplus I'd probably be able to go off grid entirely. While we generally go through 8-11 units a day depending on the time of year (more in winter, less in summer), the panels will provide as little as 3 or 4 on a really dark December day, so they can generally only supplement our needs for that month. By contrast, the highest output I've seen in summer was 28. Unsurprisingly, most of the year the output is not at either of those extremes so we don't end up sending the majority of it to the grid over the course of the year.

Thankfully I live where I was able to get a feed-in tariff, so from a financial perspective the net effect is that we're better off in the medium and long term. Nevertheless, the amount of energy needed to propel a 1.7 tonne car at 120kph for 300 kilometres is probably double or even triple what my solar array can provide on even the longest, brightest summer's day. And the array has a much greater surface area available to absorb solar energy than any car does.

unkel

mr chips wrote: »

Nevertheless, the amount of energy needed to propel a 1.7 tonne car at 120kph for 300 kilometres is probably double or even triple what my solar array can provide on even the longest, brightest summer's day.

Indeed, but there's another side to it as well. The average Irish car does 17k km per year. My car has a battery of 28kWh and a range of 240km

In other words, my car uses just 5kWh per day based on average mileage

From your production figures I guess your solar array is about 4kwp? If so, it would be able to produce 5kWh on about 250-300 days per year?

liamog

Add about 10% to for charging losses, but the principle is sound. You'd probably also want some local storage at home.

Would a Solar (DC) to Battery (DC) to Car (DC) be more efficient than the converting to AC?

ELM327

liamog wrote: »

Add about 10% to for charging losses, but the principle is sound. You'd probably also want some local storage at home.

Would a Solar (DC) to Battery (DC) to Car (DC) be more efficient than the converting to AC?

Car has an AC motor though so that would be the first (and only) conversion needed.


If you charge now at home you take DC from the sun, convert to AC during EVSE/domestic charger to charge the car, then convert to DC (onboard charger)to put into the battery, then convert to AC to drive the AC motor.


Solar direct to battery in DC would be more efficient, this is one of the many benefits of home DC charging. I often post my theory that if we do shift en masse to EVs then home charging will be done in DC

mr chips

unkel wrote: »

Indeed, but there's another side to it as well. The average Irish car does 17k km per year. My car has a battery of 28kWh and a range of 240km

In other words, my car uses just 5kWh per day based on average mileage

From your production figures I guess your solar array is about 4kwp? If so, it would be able to produce 5kWh on about 250-300 days per year?

Yeah, just under - 3.92 kwp. It produces more than 5kWh most days, tbh - even now it's usually still at 7 or 8, and I think I worked out the annual average at over 9 per day. If the output could be spread across 24 hours instead of just during daylight, it would meet or surpass our daily usage for nearly 10 months of the year. So I'm keen for battery prices to come down!

This is a bit of a sidetrack to the thread, but ... when our PV array was installed, the old analogue meter was supposed to be replaced with a digital import/export meter within a few weeks. Instead, it was nearly a year and several emails before they got round to it (I live in NI so the utility responsible is NIE).

In the meantime, the analogue meter went forward at night of course, but generally went backwards during the day - quite slowly when it was cloudy, quickly when it was bright. The only exceptions to that were when the kettle, toaster or microwave were switched on - even on a bright day, the meter would still go forward, but not race like it would when e.g. boiling a kettle after sunset*. Of course, from April to August there were a lot more hours of daylight to just keep driving it backwards, or at least continue meeting our electricity needs in the evening. Plus of course our evening usage would be much reduced at that time of year - little need for lights, spending more time outside instead of in front of the telly etc.
(*getting solar panels installed turns you into your dad!)

Anyway, the net effect of this was that by the time NIE finally installed the import/export meter, the meter reading was actually lower than it had been at the time the panels had gone live, eleven and a half months previously. And not just a bit lower, something like 200 units lower. Which was nice. Since then, we've replaced a lot of spotlights with LEDs, replaced a very old fridge-freezer with much more efficient separates, learned to not have kettle and toaster on at the same time etc so we import a fair bit less from the grid now. Even though the period of surplus really only runs from late March to early October (especially as we now use electricity instead of oil for hot water), we still exported over 800 units last year.

Back on topic - yeah, I get what you're saying about the average power requirements for driving an EV. Very few people do 200-300km every day. If I had the likes of a Powerwall - and an EV to go with it! - I could divert any PV surplus into it and use it to run the house and top up the car at night. So in theory our annual surplus which we export to the grid would meet most or all of an EV's charging needs. But since so much of that surplus is generated in the summer rather than being spread evenly across the year, we'd have to do hella more mileage during that time to actually use it all!

unkel

Nice post, particularly this bit:

mr chips wrote: »

*getting solar panels installed turns you into your dad!

hi5

Regenerative suspension should be coming eventually, would be great on some of the roads around where I live.

nsi423

KCross wrote: »

There are Plugin-Hybrids... parallel hybrid.
...
There is also the likes of the BMW i3... series hybrid

Right, of course, I didn't think of it like that before. Makes sense when you put it that way!

Is any other manufacturer doing series hybrid? It's been argued here before but I think it is a great solution while batteries are less than, say, 60 kWh. Then again I'm biased!

Even BMW are giving up on it with the new bigger battery i3, at least in Europe
https://electrek.co/2018/10/05/bmw-i3-all-electric-gas-range-extender/

zilog_jones

Mazda have been working on something for some time now, using a rotary engine of course: https://www.autoexpress.co.uk/mazda/98958/mazda-confirms-return-of-rotary-engine-as-ev-range-extender

mr chips

Huh ...

Mazda’s EVs form part of its plan for 95 per cent of its sales to be electrified by 2030, with 5 per cent being pure EVs.
Speaking at the 2017 Geneva Motor Show, European R&D boss Matsuhiro Tanaka said: “[A fully electric car] is one of the possibilities we are examining. A small car is best for an EV because bigger vehicles get too heavy with bigger batteries, and that doesn’t make sense for Mazda.”
While Tanaka didn’t go into detail on the new model, it’s expected to be a rival for the Renault ZOE.

unkel

The Japanese just don't get it. The only one that sells EVs is Nissan and they haven't been Japanese since they nearly went bankrupt and Renault bought them about 20 years ago.

Toyota, Subaru, Mazda, Suzuki, Daihatsu, Mitsubishi, etc. are all for the history books if they aim to just have 5% pure EVs by 2030. The only one that seems a bit more committed to EVs is Honda and they don't have anything close to going to market anytime soon. The Koreans are going to stamp all over the Japanese and it's unavoidable that the Chinese are coming at some stage.

zilog_jones

The Honda Clarity Electric has been out for about two years... in two states in the US... for lease only...

ELM327

zilog_jones wrote: »

The Honda Clarity Electric has been out for about two years... in two states in the US... for lease only...

Another compliance car, in the same vein as the Fiat 500e
I'll eat my hat if the two states aren't CA and OR

unkel

zilog_jones wrote: »

The Honda Clarity Electric has been out for about two years... in two states in the US... for lease only...

There's what, about 10 of these prototypes on the road?

Let's hope they are no good, otherwise Honda will end the leases, confiscate the cars and crush them. And if they are any good, why on earth would Honda want to destroy them? Oh wait.

ELM327

unkel wrote: »

There's what, about 10 of these prototypes on the road?

Let's hope they are no good, otherwise Honda will end the leases, confiscate the cars and crush them. And if they are any good, why on earth would Honda want to destroy them? Oh wait.

Don't think Chevron will be able to buy the patent this time :pac:

unkel

That was a lame excuse. EV1 was fine on lead acid batteries too. Still a lot to say for them today, but more so as home attached storage. How about a 44kWh battery for a bit over 2.5 grand? Literally weighs about a ton

Linky

n97 mini

zilog_jones wrote: »

The Honda Clarity Electric has been out for about two years... in two states in the US... for lease only...

The Clarity Electric is way behind the game. Lower range than a Leaf 24 despite being a generation newer. I don't know why they brought it out. At least you could see some sort of appeal to the fuel cell version.

zilog_jones

unkel wrote: »

There's what, about 10 of these prototypes on the road?

Over 1,500 of all Clarity variants, they're well out of prototyping. But still not generally available, and not very good.

ELM327 wrote: »

I'll eat my hat if the two states aren't CA and OR

Your hat is safe for now

unkel wrote: »

That was a lame excuse. EV1 was fine on lead acid batteries too.

Did you have shares in Chevron or something? The Ni-MH batteries for the EV1 increased the range by over double, while reducing weight at the same time. Lead-acid batteries were old hat 20 years ago, for the application in vehicles.

unkel

zilog_jones wrote: »

Over 1,500 of all Clarity variants

Yeah, and almost none of them BEV. Honda seems very shy about this, I couldn't find figures when I had a look, but I'm getting the impression it's not much more than a dozen.

unkel

zilog_jones wrote: »

Did you have shares in Chevron or something? The Ni-MH batteries for the EV1 increased the range by over double, while reducing weight at the same time. Lead-acid batteries were old hat 20 years ago, for the application in vehicles.

I know. Lead-acid batteries are crude and heavy, but the lead-acid still made the EV1 into a viable car with a reasonable enough range. And that was back in 1997. Many, many years later brand new generations of EV like the Nissan Leaf did not have a ranger longer than that of the EV1 on lead-acid. Say no more.

As I said, the Ni-MH patent was just an excuse to withdraw the car and get on with cosy high margin ICE business as usual. I'm not one to fall for conspiracy theories, but this is as close as it gets to a good one