Super-fast EVCPs?

Jon Steward:

Lithium batteries tech is very young. Lead Acid chemistry gives 1.2V per cell and requires smart conditioning to stop early death from over and under charging.

 

At the risk of appearing a bit of a nit pick, not quite so.


NiCd (nickel Cadmium) and NiMh (Nickel Metal hydride) are the ones that are more like 1.2V per cell, (oh and NiFe (Nickel Iron) but there will not be many of those left ,except perhaps on very old milk floats)

All batteries of these families have alkaline electrolytes.

These can all be constant current charged at a rate of C/10 or less, as once fully charged, the water electrolyses to hydrogen and oxygen, but the nickel catalyses their recombination back to water, just making the cell warm, so a few 100% overcharge at low current rate is not usually an issue, nor is leaving flat for a few weeks. The problem is that they are quite heavy for a given capacity. The NiCd was Invented in the 1890s,  various forms these have been around commercially since between the wars, but modern 'chip fabrication' methods now allow plates to be thinner and textured to give more area, so that capacity per cell size is about 3 times what it was in 1970. NiMh have largely driven out NiCd from common use in the last 25 years or so.


Lead Acid is sulphuric acid based and manages about 2-2.3 volts per cell. The original  wet cell concept is about 150 years old, but the modern compact ones use lead coated plates made of other things, and may have the acid in a gel or glass-fibre mat to allow it two work when not upright. Lead -acid cells must not be let to go flat, or the plates dissolve ('sulphation') and there is no cure for that. Sealed cells must be charged up to a voltage limit, and then the current cut back, or they outgas, and can blow up. Open cells may be allowed to outgas, but then you need to add distilled water to compensate. At one time all garages had a hygrometer to measure the acid strength to see how much water to add.. Now most are sealed.


Various Lithium based batteries at 3.5 to 4.2 V per cell have been around since the 1980s appearing first in a military setting, but have only really come out commercially in the last 20-25 years for phones  (where 3V CMOS allows a 'one cell' design) and laptops where sticks of 3 cells in series to give 10-12V or 4 cells for 12.5-16V  are the popular configurations.


The modern ones do not have exposed lithium inside, and the electrolyte is not a liquid but a flexible and conductive polymer, so the fire risk is not as high as the early metal plate ones (though the polymer burns nicely, it does not self ignite.).

Like lead acid they must not be allowed to go flat - falling below 2,5V off load is usually fatal, nor overcharged, so a mix of voltage limited and current limited charging is needed, with the limits being cell temperature dependant. Modern electronics can handle this surprisingly well,and if the cells are only charged to 4.1V not 4.2, and not run fully flat or over charged, you may look forward to a 10 year life or many thousands of charge cycles which ever occurs first. (for best results,  series sticks need a 'charge balancer' to leak charge from whichever cell reaches 4.2V first, so charging can continue for the other cells without over-charging that one - making the 10 cell stacks used in electric bikes quite a thing, as connections are needed to monitor each cell in the stack. Quite often this is the same chip that locks the battery off if any cell gets to the lower voltage limit, or the total charging voltage is too high.)


M.




 

 

Or just make the battery packs hot-swappable (like many a small UPS) - then you can charge them as slowly and inconveniently as you like and still fill the vehicle in a minute or two (think Formula 1 pit-stop but changing a slide-out battery rather than the wheels). I'm sure the klankeys could even automate the process so it would be a bit like driving into an automatic car-wash.

   - Andy.

I agree, a 'calor gas bottle' business model would have a lot to recommend it, the distributors  could take them to the power station to be refilled, or at least to a place with an arterial sized feed. Who knows the load could be used for grid balancing.

As far as I know, the only folk looking at battery standardisation and removable modules  are electric motorbike makers

here    and an agreement between Japanese manufacturers  here   


and  demostrated here


i cannot help feeling the current solutions are a short-lived stop gap.

Perhaps cars could be re-jigged to take 6 or 8  standard motorbike rechargeable batteries as a removable pallette  when the original batteries are no longer made.


Mike

Geof


Could you not put the generator on a trailer and tow it behind the vehicle thus avoiding having to stop to charge up the vehicle? Could be the answer to all our problems having a trailer with a generator behind every new vehicle. I cannot understand why no one has thought of doing this already?

Problem with standardizing batteries is that you would have to standardize cars. One of the problems with batteries is that they are heavy. A lump of them cannot just be put where the ICE used to be. Look at the size of the boot of battery and ICE versions of the same car. AFAIK, the cells are distributed so as to minimize loss of useful space and maintain weight distribution.


Standardizing a battery pack which is the size of a briefcase or even smaller is a different matter entirely.


If Japanese manufacturers are aiming to standardize their motorcycle batteries, good for them!

Sparkingchip was part way there with his suggestion of mini wind turbines on the vehicle roof!


I can't believe I'm admitting to this, but my first car was a Daf, the rubber band jokes were many......


Regards


BOD

P - Yes that could work quite well I think ?.


The street I live in has 30 or so houses and I am the only one with solar panels.  Most of the people who live in the street still have to go to work for a living (not me i am too old!).


If I had an electric car I would want to charge it at home and I suspect most of the other people in the street would want to do the same.  So we all install 7kW chargers and the 2 to 4 kW per dwelling that the DNO allowed when these houses were built goes out the window.


I am sure that, given the will, the required energy to power all of the cars in the UK could be obtained from renewable energy.  Especially if we made use of the fact that we live on a shelf on the east side of the Atlantic Ocean and we get a tidal pulse twice a day which flows round the country in two directions - giving us tidal peaks that occur at different times around the coast.  All of this regardless of the weather.


I can also believe that we could reinforce the national grid to deliver this energy around the country.  


The bit I don't get is digging up every residential street in the country to reinforce the DNOs networks so that energy becomes available in my street.


Hydrogen has much to commend it and, given enough development, could provide realistic long term solution.


Regards


Geoff Blackwell 

Not just cars and lorries that will need to have large batteries:- https://www.aspistrategist.org.au/wp-content/uploads/2019/08/Paul-Greenfield-Appendix-to-submarine-battery-article.pdf 

Some large capacity batteries envisaged there, never mind the jump leads........

Clive