Lithium technology (and others).

[Vikki]

What is the current state of lithium technology? It wasn't that long ago (a few years but not many) that lithium batteries were only any good for light duty but long life. They had a high mAh rating but couldn't supply much in the way of current. Now we have lithium batteries that can bang out enourmous (ish) amounts of current. Even Energiser are now coming out with high power lithium batteries (Lithium Ultimate) to power gadgets and cameras. Normal alkaline batteries have a capacity that is dependant on the load drawn over time. Look at the Duracell datasheets and they will not give a capacity, they show a graph with capacity against load.

It tunrs out that at low currents you get (say) 2000mAh. Double that current and you might get 1800mAh. Draw heavier current like some motor driven toys require and the capacity can fall to 600mAh. Now, Energiser have a graph that shows this but also shows that their lithium batteries have a stable capacity regardless of current drawn so they will state the mAh capacity of their batteries. Frankly I was amazed at what I found out about alkaline batteries and their variable capacity.

Bit of preamble here: I design electronic control systems for fire and smoke curtains. We needed to do a bumper bar sensor that fitted to the bottom of a curtain so that it would stop the curtain from coming down for 10 seconds if it hit something. I decided to use a small transmitter in the bottom bar and a 24V receiver near the control box. The transmitter runs on two 3V lithium AA size batteries and the life expectancy is 9 years with intermittent use. That's 1 year short of the shelf life. However, these particular cells couldn't provide high current unless in very short bursts. Now we ask ebike etc., lithium cells to provide high current for long periods of time. To me it seems like there's been a big leap in the technology and I wonder just how robust a technology it is at this time. It is apparent that lithium technology is advancing in leaps and bounds. This is evident in comments I've seen that say lithium batteries from a few years ago died relatively quickly while new batteries are showing signs of longer life. Is Lithium technology becoming more robust or are they about to hit the wall with it? Mix that in with Energiser who suddenly bring out high current Lithium AA cells and you wonder are larger batteries out before they really ought to be. Energiser have obviously taken time to get to the point where they feel confident in their new battery.

So, where exactly is lithium technology? Is it going to be the be all and end all of battery technology or is it a technology that has been released too soon. Too soon, there's a thing to conjusre with. It needs to be in the market place to provide the cash from early adopters to spur further research and provide better batteries. At what point do we get robust and reliable batteries? Are we there now? Am I blowing bubbles?

Discuss

Vikki.

 

[Alex728]

I do think its "getting there" but I think one very important factor with ebikes (which I also mentioned in another thread) is that the bulk of the market (and therefore investment) is concentrated amongst affluent areas of South China

Here the weather is warm/tropical - and SLA batteries from the first generation e-bikes also have short lives (a year if people are lucky?) due to this phenomenon.

So even the current lithium batteries with a 2 year service life aren't seen as such a hardship at this time. It may be only be as the European market develops and more early adopters feed back their gripes at the high total cost of ownership that there will be more impetus for manufacturers to improve.

It might be galling for Westerners to realise they are playing "second fiddle" here but I think this is definitely the case with overall ebike development.

As flecc has mentioned many times the production of decent NiMH batteries appears to have ceased - I expect the wider market forces (for batteries as a whole) play a part here as there isn't much other use for high discharge NiMH cells other than in ebikes, but the demand wasn't enough to keep production going.

I think its not all doom and gloom worldwide - comparing the cost of ebiking with single occupancy petrol vehicles may mean its still popular - and the possibility the Asian ebike markets will remain in good shape (I also expect Chinese consumers don't have their bikes/batteries waiting in containers for months!)

Hower the battery issue as well as the economic depression may well push the European e-bike market back to the lower end - with more people going for SLA based ebikes even if they are heavy and clunky - or maybe lower powered 24V bikes... at least until/if the economy improves. Perhaps maybe this (as well as the safety regs) might give competing manufacturers an impetus to co-operate on projects like Energybus (the common battery/connector project) - surely companies working as a consortium like this could have more "clout" with battery manufacturers (and provide more investment) to encourage improvement?

 

[flecc]

The main problem with rechargeable lithium-ion batteries has been the cathode material. There's around a dozen materials with some degree of suitability, and the easiest and best of those at first was cobalt which worked moderately well. Unfortunately under some circumstances these cells could "grow" metallic particles with a jagged formation which could puncture the insulating layers and cause shorts with fires of varying seriousness, even to the point of explosions.

Clearly that was not acceptable so there was a rush into the safer manganese cathode material that we knew how to use. Unfortunately manganese is a few steps lower down the efficiency scale of cathode materials, so these cells were unable to deliver current at the same rates as the cobalt ones had, and that coincided with the point where many e-bike manufacturers were switching to lithium from NiMh, hence the premature failures. In any case, both cobalt and manganese variants could only expect around 500 charges maximum and deteriorate with age whether used or not.

The best element of all for lithium battery cathodes is iron, but solving how to use it has been a long and arduous process,though we are getting there now with lithium iron phosphate cells ( LiFePo4 ). The first of these are already on the retail market and promise around 2000 charges with a minimum of 1000 charges virtually certain and a possibility of 5000 charges. The latter would make these effectively a lifetime battery for electric vehicles. It's not entirely good news though, for these cells are both bulkier and heavier than the previous lithium types, taking us back to the weight of NiMh and slightly greater bulk. So far no major e-bike manufacturer has been sufficiently satisfied with the reliability of those from trial mass production runs, and the only e-bike using them so far has been a low powered one with a very tiny form of this battery type. I think we probably have another year or two to go before we see them on major bike brands, in part due to manufacturers not wanting to be burnt twice, and in part due to the current economic climate slowing activity.

For the present we will have to use the polymer variants of the maganese type.
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[Vikki]

Hi, Alex.

I think SLAs would do rather well on the Wisper since the efficiency of the motor system is so much higher than my old Powabyke. It used to kill my batteries quite quickly. Mind you, they were of slightly lower capacity than the originals that lasted 14 months. Consequently I ran them to a greater depth of discharge than was good for them over time. Recall what I said about alkaline batteries, it is true of SLA as well except in a different way. The deeper the discharge between chargers the lower their real capacity. They start off at 12Ah but rapidly (over months) lose that capacity. Keep the depth of discharge to above half full and they last very much longer.

Quite agree with "getting there". Over the last couple of years it is apparent that they are improving. Let's hope that by the time I need a new battery they will "be there"

Battery technology really needs to move forward by a huge amount. We're all going to need high power, ultra high energy density batteries before long.

Vikki.

 

[flecc]

Battery technology really needs to move forward by a huge amount. We're all going to need high power, ultra high energy density batteries before long.

Vikki.

See my post just above Vikki.
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[Vikki]

Hi, Flecc.

That was an interesting post and I learnt a lot from that.

Edit to take in Flecc's last post:

I'm thinking of when oil becomes too expensive and rare for us ordinary Joes and Joans. Battery technology is going to become critical.

 

[Bigbee]

There appears to be huge investment in the far east,especially Japan ,in battery technology.The big car manufacturers working with major battery companies to create electric vehicles.This development must filter down to other products such as ebikes.With regards to lithium its interesting to see it coming into every day items like power tools,look out for the adverts in the papers.SLA on a Wisper Vikki is a huge backward step and should and wont ever happen

 

[flecc]

There appears to be huge investment in the far east,especially Japan ,in battery technology.The big car manufacturers working with major battery companies to create electric vehicles.This development must filter down to other products such as ebikes.

The two are not really compatible. Battery research for cars is for ultra fast charge to enable quick recharge in minutes during a journey, with bulk and weight of lesser importance.

E-bikes need a very different technology with low weight, small bulk and good range being important and ultra rapid charge not needed.

The two paths now are probably SCiB for cars and lithium-iron (LiFePO4) for e-bikes, though lithium-iron is still a contender for cars at present.

Schwinn Bicycles who are always prone to any marketing gimmick have introduced the Tailwind bike with the very unsuitable SCiB type battery, presumably in the hope it's potentially longer life will compensate for it's low energy density, but it's a dead end route for e-biking.
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[Schwinnfan]

misguided approach

Flecc, I agree that the Tailwind approach by Schwinn is the wrong one. It assumes that we all cycle point to point with a charge point available at each one.
As a general view on all the above points of view, there is one area of concern unmentioned. We are (i think) and excepting the odd crazy ebiker , rational and apparently educated peeps. But, assume for a minute the Panasonic 10A battery was 40A, an immediate discharge would be a serious explosion.
Taking my ambling thought process to ..........the United States. Over Christmas we sailed up the Rhine met some American technical peeps from Boeing in Portsmouth (UK). We discussed US armed forces, who are already limited to what Amperage per kg energy cell they can use, apparently some states definition of explosive has limited AA rechargables to max out at 1800mah, we can buy 2400 in UK in Tesco.

 

[flecc]

As a general view on all the above points of view, there is one area of concern unmentioned. We are (i think) and excepting the odd crazy ebiker , rational and apparently educated peeps. But, assume for a minute the Panasonic 10A battery was 40A, an immediate discharge would be a serious explosion.

I don't think this will be a problem though. At present the standard Panasonic unit in a typical bike has a range from 30 miles upwards, which at a typical average speed of 12/13 mph is 2.5 hours at least. A 40 Ah battery isn't needed since that would mean at least ten hours cycling.

Owners will always opt for a compact battery covering almost all of their journeys, and for those who want the odd longer journey, a second battery weighing just over 2 kilos does the trick.

I think the largest capacity we'll see will be about 15 Ah, the +40 mile range Wisper 14 Ah battery getting close to that.

Of course there is another approach to keep capacity in check, using a higher voltage. The Vectrix scooter for example uses a much higher voltage with low capacity to achieve the same ends of good range with adequate power, and it could be that future e-bikes will follow that path.
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[Mussels]

Of course there is another approach to keep capacity in check, using a higher voltage. The Vectrix scooter for example uses a much higher voltage with low capacity to achieve the same ends of good range with adequate power, and it could be that future e-bikes will follow that path.

I thought I read recently that as well as a legal weight limit on ebikes there was also a legal voltage limit of 48V, I can't remember where I got that from though.

 

[flecc]

I thought I read recently that as well as a legal weight limit on ebikes there was also a legal voltage limit of 48V, I can't remember where I got that from though.

I don't know anything of that, either in the UK or EU regulations. However, even using 48 Volts would allow a 33% increase in range for a given capacity of previously 36 Volt battery, and doubling of course on a previously 24 volt system. We'd be speaking of a 60 to 100 mile range on a Panasonic motored bike with the same 10 Ah, plenty for most.
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[Alex728]

I thought I read recently that as well as a legal weight limit on ebikes there was also a legal voltage limit of 48V, I can't remember where I got that from though.

I think its an EU reg applying to all electrical equipment, not just bikes - 48 volts is a normal safety limit on any piece of electrical equipment (Safe Extra Low Voltage) above which more safety testing / insulation is required.

48V kit is very common in telecoms...

 

[Vikki]

SLA on a Wisper Vikki is a huge backward step and should and wont ever happen

Not to the poor sap who's bike is stuck in the shed 'cause they can't afford or justify £400+ for a lithium. An SLA option could get them back on the road. Mind you, they'd need an SLA charger (not too bad for me since I have the one for Old Faithful).

I'm just thinking options (not the orange one - no, not the chocolate one either ).

I'm looking forward to a long life on my Liths and I'm putting the pennies by to cover my battery when I need it. I didn't realise in starting this thread that it would end up pointing out to me the true running cost of Bikey. 6p a mile is ace, though

Best regards.

Vikki.