Battery Advances, the Myth and the Reality

[kraeuterbutter]

but the bear !!
the bear would not be cool anymore..
so -> lithium XX batts int he fridge is no good idea !



i wonder about your calculation:

The need for the eZee models that I use is 36 volt with a minimum of 10 Ah, but preferably about 13 Ah, weighing the same or less than the present Li-ion manganese 4.4 kilos.

thats REALY heavy..
are there charger-electronics, balancing-curcuits, etc. included ?

as said, my cells will give this:
37Volt (= 42Volt after charging) with 29,4Ah !! at only 4900g
(cabable of around 300A current continously and around 500-600A substain possible)
(in reality i would get (at 10C discharge) around 27Ah out of the batts..
then considere: if you only discharge to 80% for much longer battery-life, 20Ah-25Ah are usable)

on the other hand: this are still (for now 2 years) the lightest cells on the market (highpower-cells i know)
since then, for the last 2 years all manufactors seem to have started to make more powerfull cells (i know: 300A is powerful enough for a e-bike ), witch are now about 15-25% heavier, but also twice as powerfull and longer lifetime

for motors which where also mentioned: i have no experiences with such slow-turning motors and if there are still much improvments possible...
i have build some outrunners myself (up to 600Watt continous power and 1000Watt peak)...
at least for motor with high rpms (10.000rpm - 80.000rpm) i can say:
with 300g motor there are 500Watt continously and peaks to 2000Watt absolut no problem.. motor will not overheat
so i think - also the rpm on a bike are so much slower - that there should be still some potential...
2,5kg for only 250-500Watt sounds heavy to me...

for NiMh: are there any good chargers sold with the bikes as well ?
you can improve life of NiMh with some advanced charging-processes, like
Reflex-Charging
so there should also be an eye about this...
of course, such a charger will not be possible for 30-40 Euro..
but the 50-60Euro more payed for the charger, will be safed money on the longer living battery in the long-run

 

[flecc]

but the bear !!
the bear would not be cool anymore..
so -> lithium XX batts int he fridge is no good idea !

We have a something of a reputation for warm beer in the UK!

i wonder about your calculation:

thats REALY heavy..
are there charger-electronics, balancing-curcuits, etc. included ?

Yes, all the balancing and charge electronics are part of the battery, these used with a simple stabilised charger. There's also the case, mounting arrangements and connectors, it all adds to the weight.

for NiMh: are there any good chargers sold with the bikes as well ?

Only DT/dt ones at present, some not very good, but a few are excellent. The Taiwanese Metco one used with my Lafree Twist has taken the NiMh batteries to four years and still performing well, with just the inevitable capacity loss.

I recelled one of these and the old cellpack had all the cells well within 1% voltage variation, not bad after four years. I'm using that old cellpack for other purposes and it maintains it's voltage extremely well. The Chinese higher capacity replacement charger I've identified for these batteries is also a good one with very accurate control of the temperature cutoff point.

So no complaints from me on those, hence my satisfaction with NiMh at present. A to B magazine have also reached 4 years and still working well on an eZee NiMh battery and charger. NiMh is a good reliable technology that does the job with no problems.

Compare that with my own and some others' Lithium experiences on bikes. Total failure at 4 months, 37% capacity loss in the first year, frequent cutting out under load, burnt down house, caught fire on bike.

And still you wonder why I like NiMh.
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[Baboonking]

We have a something of a reputation for warm beer in the UK!

burnt down house, caught fire on bike.

And still you wonder why I like NiMh.
.

Flecc, are you aware of this actually happening to anyone yet?

 

[flecc]

Flecc, are you aware of this actually happening to anyone yet?

Warm beer, yes from past personal experience of British pubs.

Burnt down house, only from the reported case in Germany.

Battery catching fire, from reading some reports and allotmenteers case of fire in one cell of his bike's battery reported in this forum.

Two out of three certain is good enough for me, also two of the Li-ion battery in use experiences are mine and a third reliably verified.
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[allotmenteer]

See http://www.pedelecs.co.uk/forum/electric-bicycles/195-dangers-li-ion-batteries.html for further information on my li-ion pack failure.

 

[Baboonking]

serious stuff. house fires not nice. I'm a bit skeptical about li-ion cobalt packs being sold as a consumer product.. So many differnet ways for them to explode. I suppose a good question to ask before buying a lithium battery bike is 'would your liability insurance cover if me if my house burned down'

 

[flecc]

serious stuff. house fires not nice. I'm a bit skeptical about li-ion cobalt packs being sold as a consumer product.. So many differnet ways for them to explode. I suppose a good question to ask before buying a lithium battery bike is 'would your liability insurance cover if me if my house burned down'

I suppose bike batteries could easily include a sparklets style small CO2 cylinder with heat sensor to cool the content instantly and extinguish any burn, with thermal fuses tripping main connections.
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[Baboonking]

apparently co2 wouldn't work. U need a type d fire extinguisher!

Laptop Battery Fire Video

 

[flecc]

Yes, I knew about that one, but inside a sealed battery case the extreme cold of the discharging CO2 would chill the contents, dropping the temperature very rapidly and would extinguish fire in the absence of oxygen.

CO2 in free air conditions is often completely ineffective, it has to be confined to the fire zone.
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[Baboonking]

Sounds good,

I don't think I'd be comfortable with a li-ion cobalt battery unless it had a physical method of preventing fire in the case of a thermal event, its simply too risky to rely only on the BMS. Something like your co2 chiller. The other trick I've seen is liposack LipoSack.

 

[flecc]

That seems like a good idea, but the best bet will always be a steel or other fireproof box or cabinet.

But as I've been saying to kraeuterbutter for a couple of weeks now, NiMh does it for me. These newer technologies either catch fire, are too weak to deliver the current without dropping to voltage cutoff point, and are often finished after less than two years.

I'd rather just carry the extra one kilo, get there and back without stopping through cutoff, and then sleep peacefully, assured of my battery and bike safety and the fact that NiMh lasts four years for me and others, and is cheaper to buy as well.
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[Baboonking]

Same as, I've had really good experience with nimh. It just worries me that companies are selling li-ion cobalt batteries

 

[flecc]

Same as, I've had really good experience with nimh. It just worries me that companies are selling li-ion cobalt batteries

And now Lithium-ion Polymer (Li-poly), which as kraeuterbutter observed are capable of a total lithium burn if the management control is less than perfect. Three or four kilos of lithium going up in flames would be something to really fear.

I think that some companies might have to learn a very hard and costly lesson over the next couple of years.
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