Electric Transport-Charging Times-what am I missing.

[Kudoscycles]

What am I missing.....If we have a 10Ah battery and a 2 amp charger,it takes 5 hours to recharge.....If we have 2x5Ah batteries and 2x2 amp charger,we can recharge in 2.5 hours....If we continue,why can't we have cells or at least a group of cells that have an inbuilt individual charger and put 10Ah into the battery in say 10 mins.
This is so relevant with electric cars,why can't we charge them quicker? Why does it take overnight to charge the vehicle.
Obviously I don't understand something otherwise I am sure the Nissan Leaf would have 30 minute recharges.
KudosDave

 

[Deleted member 4366]

Cells have a maximum charging rate, which depends on their chemistry. Your example is not correct. Assuming that your 5aH and 10aH batteries have the same cells and that you're charging them at the maximum recommended rate, the 5aH one would have to be charged at half the rate, or the 10aH one could be charged at double the rate, so the charging times would be the same.

 

[RobF]

I don't understand the physics, but one of the good things about my Bosch bike is it charges in three or four hours.

My Brompton Nano seems to take an age.

 

[Kudoscycles]

D8veh....if you charged one individual cell,do you know what is the minimum time for charging that cell,at maximum rate?
KudosDave

 

[Deleted member 4366]

It depends on the cell. The charging rate used to be generally, now 0.4C is becoming more common. A123 cells can go as high as 10C, so if you went to the expense of a 90 amp charger, you could charge a 9aH battery made with these cells in 6 minutes.
A123-3.3VB Lithium Ion 2300mAh Single Cell Battery
The problem is that the charger would cost £500, so it'd be cheaper to have a spare battery charged and ready.

 

[RobF]

Wasn't there a very fast charging battery from, I think, Toshiba?

Something rings a bell about it being fitted to a Schwinn ebike.

Again from memory, it charged OK but didn't perform well on the bike.

 

[Yamdude]

I've always thought it was bad for the batteries to be charged too fast..... seeing as even mobile phone batteries take at least an hour to charge.
Also, I now only use rechargeable aa and aaa batteries in radios, bike lights and torches. When I've charged these in fast 15 or 30 min chargers they get incredibly hot, so I use the slower chargers now.

 

[banbury frank]

Hi Headway cells have a max charge rate off 10 C so ther 10 AH cell can be chargerd safly at 100 amps so in 10 min Or a pack off cells say 48 volt 15 AH the same 150 amps max total yes they get HOT and the battery life is halved from 2,000 charges been ther done it BUT the cells are to big and heavy we have bikes out ther using 60 volt 16 ah cells Pack with controller 16 kilos one customer has 2 on the rear rack 100 miles NO pedaling top speed 43 MPH 15 AMP chargers still going strong after 3 years

so a BMS charger 48 volt 60 amps will charge a 15 ah 48 volt pack no time

Alloy Shell 4KW LiFePo4/Li-Ion/Lead Acid Battery EV Charger - BMSBATTERY


Frank

 

[patpatbut]

Hi Headway cells have a max charge rate off 10 C so ther 10 AH cell can be chargerd safly at 100 amps so in 10 min Or a pack off cells say 48 volt 15 AH the same 150 amps max total yes they get HOT

so a BMS charger 48 volt 60 amps will charge a 15 ah 48 volt pack no time

Alloy Shell 4KW LiFePo4/Li-Ion/Lead Acid Battery EV Charger - BMSBATTERY


Frank

Hi Frank,

Just wondering such a high charging current would it reduce the charge cycle of the battery?

Pat

 

[banbury frank]

Hi Pat just updated the post yes it will cut the life in half

our new 70 volt 15 ah battery is only 5.5 kilos we use a 8 amp charger this is aprox 1/2 C so safe we can charge at max 1 C

Frank

 

[flecc]

Wasn't there a very fast charging battery from, I think, Toshiba?

Something rings a bell about it being fitted to a Schwinn ebike.

Again from memory, it charged OK but didn't perform well on the bike.

Yes, it was a lithium-titanate battery, trade name SCiB (SuperCharged ion Battery). Charging in about half an hour, it's big disadvantage is that it has only half the capacity for a given bulk and weight. It was fitted to a Schwinn Pacific with a Tongxin Nano front hub motor and low power controller to get enough range from it's small capacity.

In fact this is true for almost all batteries, the faster the charge wanted, the lower the cell content density necessary to prevent chemical stress and overheating when charging, and therefore the lower the capacity.
.

 

[flecc]

This is so relevant with electric cars,why can't we charge them quicker? Why does it take overnight to charge the vehicle.

Two ways to obtain very fast charging Dave. One is to have low cell content densities which has the disadvantage of a much larger, heavier battery, the other to use loads of very small cells. The Tesla sports e-car uses this latter method with over 6000 cells, the disadvantage being very complex charging arrangements and very high cost.

Toshiba have intensively researched fast charging for many years and in their hands lithium polymer batteries were a fast charge type at first before they gave that up in favour of trying other methods.

All fast charging is a dead end though, we couldn't supply the vast currents needed to charge 10 cars pulling into a refuelling station at any one time.

Ten little Nissan Leafs charging in 15 minutes would need over 5000 amps from a 220 volt supply. In practice every "filling" station would have to be fed with very high voltage supplies from the national grid and have their own large substation with huge oil cooled transformers etc.

Hopelessly impractical, not to mention the trebling of power stations we'd need for e-vehicles to take over from i.c. ones.

 

[KirstinS]

Very interesting thread

I always thought lithium chemistries could only be charged fast up to about 80% and then a tapred charge was required - so true fast charging to 100% was not inherently possible ?

 

[trex]

the only way to fast charge is via fuel cell. That's where the future of ev is.

 

[Geebee]

The problem with fuel cell technology is that there is an extra step in the generating to using proccess and at the moment it is an expensive step.http://www.spiegel.de/international/world/toyota-develops-new-fuel-cell-car-a-930834.html

"As tempting as the short refueling times and large ranges of a hydrogen fuel cell vehicle are, this energy footprint is also a substantial deterrent. To be climate-neutral, hydrogen has to be split from water using green electricity. Then it has to be transported, condensed to the enormously high pressure value of 700 bar, converted back into electricity by the fuel cell in the automobile, and then converted into motion.

About 70 percent of the energy is lost along the way. In an electric car, which is charged slowly, thereby saving electricity, more than 70 percent of the energy is utilized. But from Toyota's perspective, this enormous benefit is worthless if the result is not a fully-operational car capable of traveling longer distances."

Plus fuel cell construction is still expensive.

"TOKYO -- By the time Toyota's first hydrogen fuel cell vehicle goes from this year's early prototypes to serial production in early 2015, the company expects to cut the cost of producing the powerplant in half -- to about $51,000 -- and to halve it again by 2020, a top executive said.

That cost reduction will allow Toyota to start selling the vehicle for between $50,000 and $100,000, said Satoshi Ogiso, managing officer of Toyota Motor Corp., who oversees alternative vehicles, powertrains and chassis development.

Read more: http://www.autonews.com/article/20131014/OEM06/310149959/toyota-predicts-big-cuts-in-fuel-cell-costs#ixzz2lc0ZMsHW
Follow us: @Automotive_News on Twitter | AutoNews on Facebook"

I personally like the Mega pixel concept, a decent electric range and a tiny extender generator, I think from memory they were talking 100+ km ev and 900+ km extended range, plug in over night would do 90% of usage but the range is there for a full day trip.

As for bike recharge time, do most need more than a single charge range every say 8 hours? if so there is always the option of a second battery if it is not one of the stupidly expensive ones.

 

[trex]

as flecc pointed out, the problem is the power grid. You can easily transport chemical fuel around the country, a petrol station serves thousands of cars a day and fill £50 worth of petrol in a minute. That's a lot of power, about 20MW per car.
To serve a similar amount of cars, you'll need a substation attached to the petrol station and increase the capacity of the grid enormously or have the generator built into the gas station. Whichever way, until you have Star Trek technology, we are stuck with chemical energy as distribution medium.
The fuel will be produced with solar energy in deserts. It may be hydrogen or liquid metal but it will be cost competitive against fossil fuel.

 

[mike killay]

Another thought re hydrogen,
Why not just burn it in an internal combustion engine?
No need for a fuel cell

 

[Electrifying Cycles]

Personally I think hydrogen is a better fit for cars, yes there are issues but if adopted you could top up in a short time like petrol. Also some new cars with the system being developed, Japan does appear to lead the way at the moment in this area.
http://www.washingtonpost.com/business/technology/toyota-unveils-hydrogen-car-for-2015-at-tokyo-auto-show-as-competition-steps-up-in-fuel-cells/2013/11/20/594a26c4-51c2-11e3-9ee6-2580086d8254_story.html

 

[trex]

Another thought re hydrogen,
Why not just burn it in an internal combustion engine?
No need for a fuel cell

You get a lot better yield converting H2 directly to electricity with fuel cell than burning H2 in an ICE.

 

[flecc]

We've had eight Mercedes hydrogen fuel cell buses in regular service in London now for three years. Used mainly on tourist routes for obvious reasons, they've had the odd teething problems but have been good enough for there to be a desire to expand that fleet.

Cost of bus and current fuel are the main problems, the single decker buses are one million pounds each, which would buy three normal double deckers.