Batteries - but not the ones you're familiar with....

rog_london

Esteemed Pedelecer
Jan 3, 2009
764
2
Harrow, Middlesex
I've been reading an article about the developments in battery technology and really it's more to do with 'green' cars than anything else, but interesting, so here's a resume which might interest you:

The Nissan Leaf and the Ford Focus Electric both use lithium-ion batteries, and there are other models from many other manufacturers which do the same. However, the cost of these is so eye watering that it's likely there won't be a big market any time soon, in spite of the rising cost of road fuel. The 16kWh battery to be used in the Vauxhall Ampera hybrid car comes out at around £20,000. In spite of that the energy density is abysmal, as the battery weighs in at about 182 kilos and the vehicle has a range of around 40 miles. Recharge time is about three hours, limited more by the capacity of your average domestic power supply than anything else. From a 13 amp socket you'd be looking at more than double that.

The alternatives, while interesting, are even worse in practice. The molten salt battery has a good reputation in industrial applications, as it has a comparatively high energy density and peak power rating. It is also reliable and has a long life. It has been used in a few cars, but of course there's a big snag in such an application and the clue is in the name - it operates at around 270 degrees Celsius, and the problem with that is that some 14% of the available energy stored is used every day just to maintain that internal temperature. It would probably be viable if your car were in more or less constant use - which is why it's not uncommon in industrial applications.

Apart from that, there are technologies described as 'promising', and I suspect we all know what that means - we should live long enough to see them in the real world. They are for the most part based on lithium ion, so not too different from what is around at present.

So, we're stuck with what we know - good old reliable and relatively cheap lead acid, which is seriously heavy related to storage capacity, and of course the lithium-ion batteries we use in countless gadgets and also ebikes. Still, if you just have to drive a car, and by next year you might be paying £100 every time you fill the tank, perhaps the cost of a decent traction battery in a car won't seem quite so bad....

Personally, I'm more than happy with the motorbike, the ebike, and that most cost-effective modern aid to travel we have in the London area - the jolly old Freedom Pass, aka the Old Gits' Travelcard. Even without the expense, there's no pleasure driving in London in any case.

Rog.
 

flecc

Member
Oct 25, 2006
50,676
28,509
Yes, the molten salt batteries are so limited in application that I'm surprised that Smart and the Think car people chose to use them, but not surprised that they have only been released a small batches of selected users.

One you left out of particular relevance to e-bikes, NiMh. Many of us mourn their giving way to lithium entirely. Their very long life in occasional use applications isn't matched by lithium, except where the enregy density is very low and weight high as in the car batteries you remarked on, both factors no good for e-bikes. Although NiMh are about 50% heavier than lithium, they are still very much lighter than lead-acid.

When good very high discharge NiMh cells were still available, the eZee choice of both them and lithium was ideal, lithium with a two year life for the daily rider, NiMh with a several year life for the intermittent user.
 

rog_london

Esteemed Pedelecer
Jan 3, 2009
764
2
Harrow, Middlesex
One you left out of particular relevance to e-bikes, NiMh. Many of us mourn their giving way to lithium entirely. Their very long life in occasional use applications isn't matched by lithium, except where the enregy density is very low and weight high as in the car batteries you remarked on, both factors no good for e-bikes. Although NiMh are about 50% heavier than lithium, they are still very much lighter than lead-acid.

When good very high discharge NiMh cells were still available, the eZee choice of both them and lithium was ideal, lithium with a two year life for the daily rider, NiMh with a several year life for the intermittent user.
You're right, Flecc. Both NiMh and NiCd could have amazingly long lives if used right. That's the crucial thing. NiCds really need to be cycled fully on a regular basis, less important with NiMh. I had a Remington rechargeable shaver for about 15 years, in regular use. I never charged it until it was flat and then made sure it was fully charged. Under those conditions the usually mythical 1,000+ charge cycles becomes a reality. Ideal use - a reasonably gentle recharge cycle, and short-term medium-current loading.

Rog.
 

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