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back to article Nanocapacitor slab to boost car batteries

Australian company CAP-XX has announced a supercapacitor module for cars that it hopes will take a load off chemical batteries. Capacitors are common in most electronic devices, thanks to their ability to hold a small charge for a short time. CAP-XX's current schtick is making very small and thin capacitors which, thanks to some …

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Stop-Start

I always wondered what stop-start cars did when stuck on the M1 for an hour.. do they really restart the engine every 2 car lengths and are they clever enough to know when stopping it means it might not have the juice to restart it?

Now I don't know how tight a seal the piston rings make but I'd have thought stopping the engine with a cylinder fully injected at top-dead-centre would perhaps allow you to restart the engine by kicking a spark into that cylinder if the engine was warm, rather than cranking the starter motor, allowing for many more restarts. Maybe the fuel vapour condenses too fast in the cylinder when left unignited.

Perhaps that's how they work. Dunno.. Ramble ramble

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Re: Stop-Start on the M1

I suspect the charge in monitored, and if it falls below x% the engine just keeps on running (at least until x% is exceeded).

They'll probably use what my technically-challenged colleague refers to as 'computers and shit' to make it work.

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Anonymous Coward

Re: Stop-Start

My Stop-Start will restart the engine if its been left "stopped" for more than a couple of minutes with the lights, air-con on etc... it then doesnt "stop" again for a while so I presume something is charging back up or its reducing wear?

The manual says not to use Stop-Start if you are not going to be stopped for more than 30secs as it uses more fuel than just idling.

Either way most of the time I either deactivate it, or just leave the clutch up which stops it turning the engine off. Seems a pretty pointless invention to be honest..

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Flame

Re: Stop-Start

In short, yes, the fuel vapour essentially condenses after a certain amount of time. We take it for granted because they've been around for so long--and particularly with modern ones, work so reliably--but an internal combustion engine relies on some pretty tight timing for the whole thing to work.

"Flame" because, well, that's what's going on inside the engine (not "explosion" - that's bad).

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Re: Stop-Start

Thought as much. Shame as maintaining an ignitable compressed mixture at TDC could be a pretty efficient stop-start strategy. No good for diesel, though, either I spose.

Hohum, back to the drawing board!

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Re: Stop-Start

A fellow who owned a vintage Roller said (and demonstrated to me some years ago) that it was possible to stop the engine at TDC, and by simply switching the ignition back on would create a spark that would fire the engine.... Granted there was only a few minutes 'down time', but impressive none the less.

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Re: Stop-Start

If you could stop the engine with an air charge in there as a lot of modern engines are direct injection (petrol and diesel), maintaining the fuel rail pressure would be more effective.

Then squirt and ignite when required.

Engine would have to beyond tdc otherwise it may try and turn backwards.

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Re: Stop-Start

I know there is at least some leeway in how long the fuel mist will linger. After all, that's how most piston aircraft engines work: you prime the engine by manually injecting fuel into the cylinders, and then crank the starter. But if you wait too long after priming, it's just raw fuel sitting there no longer vaporized, and it's vaporized fuel that burns, not liquid fuel.

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Re: Stop-Start

I believe there was just such a trick with the Rolls Royce Silver Ghost, that would have to be hand cranked, in the pre-WW I days before electric start was common,

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Stop and start = new batteries

So we came up with some legislation to reduce carbon emissions and consequently we now have a bunch of burned out batteries to chuck into a landfill.... progress.

This capacitor milarky sounds great though.

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Re: Stop and start = new batteries

Well if they're lead acid batteries then they're recyclable. Easiest way to encourage people to recycle is to stick a £20 deposit on them which you get back when you drop them off at a recycle centre or replace them in a garage / Halfords.

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Re: Stop and start = new batteries

Yeah, and not just the batteries, and the dealers cost to replace them. What about all those catalytic converters and diesel particulate filters that never get properly warmed up and stay warmed up, so fail much sooner than they normally would? Plus all those acidic exhaust gases that now get to condense in the exhaust system and cause it to rust much quicker. Plus what does stop/start tech do to the life of a starter motor? Given that a starter motor doing a few starts a day lasts for, lets say, 120,000 miles, do stop/start ones last for only 20,000 miles?

Manufacturers seem to love to spend OUR money on waste of space technology, 'cause it reduces their CO2 figures by a few g/km or saves £50 a year road tax, but adds hundreds, if not thousands onto the total costs of ownership of a car over its lifetime. And don't even mention the hassle of having it go wrong at the most inconvenient moment..... Having a lazy starter motor is one thing when you are sitting in a car park and take a few attempts to get it engaged and going, it's another entirely when you are stop/starting along a busy motorway or at a busy set of traffic lights.

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Anonymous Coward

Re: Stop and start = new batteries

I designed a 1KJ super cap pack for one of my (our) systems that needed to operate from a temperature range of -40C to 85C. Total BOM cost was around $60 for quantity 5. At volume it would be near $10. Not talking about start stop but super cap packs mean don't need as large batteries and they be designed to cycle more deeply without failing since the caps provide the instantanious current needed to start shit. This is useful tech.

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Re: Stop and start = new batteries

Automotive is -55c to +125c

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Joke

Capacitance in uF or...

it didn't happen :-)

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Re: Capacitance in uF or...

rated at at least 14 volts and 150 farads according to the linked video.

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Anonymous Coward

Re: Capacitance in uF or...

And 4.7mΩ ESR. So at 800A cranking current, that's about 3kW dissipated /inside/ the capacitor. Hope it stands up to heat well as I wouldn't want to see that one go pop.

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800A ?? Shocking (eeew crap pun)

Eh?

On my old Honda the starter motor fuse is 60A, dunno what the Jag is, will be more but I'm pretty sure you don't need 800 amps to turn a V8 over, either. Unless you mean *literally* flip it over...!

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Anonymous Coward

power

800 amps in 5 feet of 6 awg wire would dissapate ( (800 ^2) * 3.2mΩ ) = 2KW. Consiering the mass of the wire that seems fine. 800 amps seems high to me but I know jack shit about cars.

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Anonymous Coward

Re: 800A ?? Shocking (eeew crap pun)

Unless I misheard, he says peak recorded cranking current was 800A towards the end of the video. That's a Subaru flat four unless I'm mistaken, so expect a big Aussie V8 to be a bit more than that.

Also, just FYI, cars don't have a fuse in the starter motor circuit due to losses caused by the enormous currents involved. The thought always makes me slightly nervous when I drive a big Beemer or Jag where the battery is at the opposite end of the vehicle to the engine.

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Re: power

Remember, this pack is intended to power all the electric accessories (including electric cabin climate control) while the ICE is powered down, and still have enough power left to start the engine multiple times (7was mentioned, but I would assume that that is if you haven't been sitting around for ages running your car's AC). In normal use, you wouldn't see that much power used "in one shot," anymore than you would drain a fully charged car battery completely dead just turning your traditionally configured car over once.

-d

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FAIL

when in doubt, complicate.

batteries dont work. Not enough range.

So lets add an engine to charge the battery.

Of bosoms,. battery wears out with all that cycling.

Lets add a capacitor as well!

Yewoo! Now we have a car that weights twice as much as it used to, and on any significant journey uses more fuel!

Gotta love green solutions..

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Re: when in doubt, complicate.

- Significantly extend battery life time, especially in pathological cases.

- Capacitors of a similar size to a battery typically weigh a lot less.

- Capacitors typically have a much larger operating temperature range.

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Re: when in doubt, complicate.

Super and ultra caps have much less temp range than Al-Elec. You can get -40 to 85 C but you have to be very careful with the voltage at the high temps.

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Mushroom

I think the real answer

Is the internal combustion nuclear fusion engine.

Instead of drving the wheels, the battery drives a high power laser that hits a spallation target at top dead center causing a pulsed fusion reaction that drives the piston. ....

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Re: I think the real answer

....... must be the flux capacitor. Added advantage that it doesn't matter how long the journey takes, you still arrive on time.

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Anonymous Coward

Stack of DVD cases

Is that a new standard unit for measuring the physical size of a capacitor? What's that equivalent to in Areas of Wales or Elephant Tadgers?

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MJI
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Car life

I reckon stop start will kill engines

Not getting as hot, exhausts will rot.

But I reckon starter motors wil fail regularly

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Re: Car life

This entirely depends on how well the engines are designed for it. A huge number of tricks, ranging from pumping the oil for a second before sparking the engine to using fairly complicated logic to determine when it is appropriate to stop-start the engine can eliminate much of the actual engine wear we would normally associate with this sort of usage. MUCH larger starter motors, in the "small traction motor" range, can provide stop-start capabilities while actually extending the life of the engine by doing a better job at smoothly pulling the engine up to idle speed - all while outlasting the engine itself (if not overloaded, well-built electric motors are very durable).

Exhaust systems are probably going to be the biggest long term bugaboo, and even on those, a lot of start-stop systems don't kick in the stop-start feature until the entire system is "hot" just for engine and exhaust life - again, good algorithms make the difference. That said, a very real question is just how much real return we'll see from all of this. In some areas, probably quite a bit - but I can't help but think that for most people, in most places, we'll just be paying for greater complexity that we don't need, because we simply don't do that much stop-start driving anyway.

-d

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Re: Car life

Are manufacturers such as BMW using additional electric oil pumps with their Efficient Dynamics enabled cars? The engines sound like they start as soon as the driver pushes the gas pedal. That doesn't give time for the oil squirt you are talking about. Considering a huge percentage of engine wear comes from starts... I mean it is not a completely dry start since the engine is warm and the oil is just draining away, but it sure isn't up to operating oil pressure.

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Happy

Re: Car life

Stop/Start on my car.

Doesn't operate below 4c.

Doesn't operate when engine is cold.

Doesn't operate when AC is on.

Doesn't operate if you travel less than 100 metres since last triggered or you don't exceed 20kph

Doesn't re-start engine if you undo drivers seatbelt or open a door.

Re-starts after about 2 mins anyway, about the max time a red traffic light displays.

Currently at 95,000 miles in a little less than 2 years. No signs of battery problems.

The trip computer average mpg reading is better driving through city centres with stop/start activated than without. On testing it over a week or two when it was new, I found my 55mpg average over a 95 mile journey, the mpg average dropped on the final 5 miles of city driving by up to 3mpg. With stop/start enabled, that drop was never more than 1mpg.

That's about 20 miles of range difference per tank of diesel on three tanks per week.

Probably not a big economic difference if you do an average 30-40 miles round-trip daily commute, but noticeable if you are a relatively high mileage driver. Road fund licence, £30.

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Happy

Re: Car life

Thanks John, I have always wondered what real world numbers were for start/stop cars.

I'm old school, the first thing my high-school auto-shop teacher told us was "the engine has it's hardest time during start-up, due to the lack of oil circulating." So I always wondered if it was worth it.

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Re: Car life

I see what you're doing there, that's a haiku - yes?

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One billion dollars

If you try to buy prototype capacitors from CAP-XX, you'll find that they're tiny surface mount components. 2.4F; 2.75V; ESR - 26 mΩ; 39.00mm x 17.00mm x 1.85mm; -40°C to +85°C, $16.25 USD. Those are great specifications, but the price is crazy. BTW, 1990 posted to a BBS that it wants its video back.

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Boffin

Automotive electronics companies provide *special* kit for stop/start options.

Revised EMU, beefed up starter/alternator, deeper discharging battery. It's a bit more than a switch wired to the clutch and a motion detector.

I believe catalytic converter heaters are SOP on high end cars these days to *avoid* the poisoning and poor efficiency that comes from running them cold, something more common in Europe, where certain pollution control options were outlawed in favor of the cat.

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Total stored energy is the same as a low cost cell phone's battery

Some numbers from the video:

Voltage at beginning: Vb = 14V, Voltage at the end: Ve = 5.9V, Capacity: C = 150F

A little calculation gives this:

Stored charge: C*(Vb-Ve) = 150As/V * 8.1V = 1215As

Stored energy: Q = C * Vavg = C * (Vb+Ve)/2 = 1215As * 9.95V = 12089Ws = 3.36Wh

The total stored energy in that huge (& expensive) capacitor bank is comparable to energy stored in a 900mAh Li-PO (or Li-Ion) cell of a low end cell phone:

For comparison energy stored in batteries:

Samsung Galaxy S2: 6.1Wh

iPad2: 25Wh

new iPad: 42.5Wh

small car battery (55Ah): ~550Wh

large car battery (100Ah): ~1kWh

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Meh

Capicitors. It's not about energy stored, it's about *rate* of release

That's the *tough* part.

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