Advances in battery technology

[kraeuterbutter]

and a example from the real world:
bike with A123

Gary Goodrum (Ggoodrum) from www tppacks com (he normaly sells thunderpower lipoly-batteries)

has done a e-bike conversion with A123-Fepo4-round cells..
he uses 16s6p A123 Fepo4 Pack for his e-bike

the cells weight 6816gramm
capacity: 13.8Ah
possible Amps of the pack: 540A peaks and 300A continous
possible poweroutput: 20000Watt peaks and 12000Watt continouse
(so, no bike would be a problem for that pack)

The bike has a 2500W brushless hub motor on the front wheel and uses a 48V controller. Using a 16s a123 setup matches the discharge profile for a 48V SLA configuration pretty close, which is why he uses one of the chargers typically used in this application.
He weights 250pounds, and the bike goes up any good size hill, accelerating while doing it !

Yesterday he went on a ride for about 10 miles, roundtrip, and it was very hilly. He had a WattsUp hooked up in the bike which reported that he hit a max of 2475W and used 6433 mAh, or about half the capacity. That says his 13.8Ah should be good for about 20 miles, maybe a bit more with flatter course, and/or some "collective management".

he will post pics and maybe even video next days..

2475Watt sounds like a lot for a ebike.. at least: its like nothing for the 7kg battery-pack, because they are able to be emptied within 3min putting 12000Watt out if neccessary

 

[JohnInStockie]

What does this tell us, anything?

Sorry maybe I am missing something here. I have an NiMH battery, 24V 6.5Ah. It can power a 186W motor for roughly an hour, cover approx 17 miles with me on it (weighing 16.5 stone) and my kit (another 20 lbs).

NimH batteries seem to be pretty resourceful, generally.

The only thing I can see as a difference is the charge time, and isnt that down to the type of batteries being used, not really the technology?

I am a simple man, and dont understand many things in this world, but as I cant have anything more powerful than a 250W continuous motor in the UK, I dont understand where there are any leaps here. If this mean I can recell my 24V Nimh D cell battery and get 13.8Ah or even 20 Ah, then thats fantastic. Does it mean that?

One thing though, my battery weighs only 4.5 kilos, not 7 kilo's like that one.

John

 

[Ian]

I think John, from reading between the lines that the battery pack in question is 48V so it will store twice the energy of a 24 pack with the same Ah rating.
I agree with you about NiMh though, not the lightest but they are proven and reliable.

Before I spend a lot on newer battery types I'm going to want a watertight guarantee that it will last. So far my own experience of lithium, and that of at least one other member of this forum is not promising.

 

[allotmenteer]

I agree with you about NiMh though, not the lightest but they are proven and reliable.

Before I spend a lot on newer battery types I'm going to want a watertight guarantee that it will last. So far my own experience of lithium, and that of at least one other member of this forum is not promising.

I'll second that! On my 14.89 mile commute yesterday my 6.8 Ah li-ion gave up the ghost at the 7 mile mark. Just as well I had the 8 Ah powacycle Nimh battery in my pannier! I find that the 8 Ah Nimh has so much more usuable capacity than my li-ion. The li-ion gets chemically exhausted very easily whereas the Nimh just goes on and on.
I'll not be buying any kind of lithium battery again, at least not until I hear of more positive experiences with them from forum members.

Lithium may be light, but a light, flat battery is not much good to anybody.

 

[kraeuterbutter]

i see your arguments..

i read in this forum two things:
1.) Lipos do not have the power of NiMh.. with a NimH/Nicd you have more power at 30-40A load in your bike

2.) lipos are dying very fast


This two statements made me to jump into the forum.
i have not much experiences with e-bikes (driven 3 for testing but don´t own one by myself yet)

but i have a lot of experiences with batteries..
Nicd, NiMh, Liion, LiPoly, LiMn and Fepo4
some of them also in competition-situations

the thing is: the cells you get sold in the bike-stores are very weak cells..
1C or 2C cells only ! (1C means: discharge is allowed to be as high as capacity, 2C means: dischargecurrent is allowed to be 2times as high as capacity: 2C 8Ah battery --> dischargecurrent should not be higher than 16A)

for that you can bring this LiPos or LiIons even in a (weak 500Watt) e-bike to the limits and shorten livetime of the pack..

i was using 2C Lipos 5-6years ago.. they were very fragile.. often they were dead after 30-50cycles !

the Point is for the A123 Fepo4
that are 20C cells.. (can put out 20times of amper then there capacity-rating)
yes, that is power (several 1000Watt) you don´t need in a e-bike
but for that: in a e-bike the batts are not at all stressed..
(so you can expect more than 1000cycles with them)

the other point is:
Calender Life-time (i don´t mean cycles here):
normal lipos and many LiIon do degenerate after 2-4 years.. so: damaged/dead after 2-4years because of a intern chemical reaction..
NiMh do hold longer.. there the mark is around 6years..
newer, higher-capacity NiMh are unfortunatly more fragile (they answer too deep discharge much more with damage than the older, not that high capacity-nimh did)

the A123 is rated for over 10years, so far over the battery-life-expectancy of Lipos and also over NiMh

and for cycle-life:
over the last 3-4 years our internet-community has tested several doozends of different lipos for lifetime..
resüme is (we stress the batts much more than it will happen in a ebike)
so far we had never a battery that made so many cycles at such cicumstances like the Fepo4
cheap china-lipos often fail after 50cycles
good and expensive lipos hold around 100-150cycles
Kokam LIpos there are many with holded even over 200cycles at same conditions
than there are the Konion, LiIon-round-cells on Lithium-Mangan-basis which managed to get 250-300cycles at same condition (they are also the only cells on the market sofar, which realy don´t needs any balancer unit and are very safe (no fire, no termal runaway))
and then there are the A123 that showed a battery-life of over 800cycles at same conditions (and over 1000cycles at little lower discharge-currents)
for Nimh: they loose after around 50-100cycles at such circumstances power/punsh and single cells in the pack start to fail after 200cycles
no pack reached ever more than 300cycles (many fail before they reach 100cycles)

this cells were all tested at much higher currents than you will see in a e-bike..
so in a e-bike they will live longer because less stressed..

A123: they have a very high Power-density
(count with around 1800Watt continouse power/kg for A123 Fepo4
compared to around 150-250Watt/kg of the best Lipos you get for your bikes (2C Lipos).. many bike-lipos even don´t manage to reach that)

downside of A123: energy-density
its not close to that what we are used to get with Lipos..
A123 have a energydensity more comparable to NiMh than to Lipos

 

[kraeuterbutter]

@John in stocky:

Sorry maybe I am missing something here. I have an NiMH battery, 24V 6.5Ah.
NimH batteries seem to be pretty resourceful, generally.

.....If this mean I can recell my 24V Nimh D cell battery and get 13.8Ah or even 20 Ah, then thats fantastic. Does it mean that?


....


One thing though, my battery weighs only 4.5 kilos, not 7 kilo's like that one.

well: your 4.5kg battery replaced by A123 would mean:
8 A123 Fepo in series (would result in ~27Volt noload and 24Volt under load-voltage)
and the cells paralleled 7times..
the cells will weight then 3,9kg (+ 600g casing we are at 4,5kg)

so: better voltage than your 24Volt-pack (which will under load be only around 22Volt i guess)

and not 6,4Ah but 16,1Ah
unlike Lipos you can empty the A123 pretty far without damage..
emptying this pack down to 16-20Volt would be ok
when you charge immediatly after you have emptied them even a empty-voltage of 8Volt on that cells would not do much harm to them !!!
but its of no point, because when the pack would go under 20Volt there is barley 1% capacity left..

so to summ it up:
at same weight you would get 16,1Ah instead of only 6,4Ah
at better voltage and Power (7000Watt continouse poweroutput would not stress that battery )
(with the lipos you get int he bike-shops you have to fear to stress the pack to much when going up a steep, long hill - fear to damage the battery
==> not with the A123...)

and battery-life is for sure also greater than on your NiMh..
when you realy get 1hour drivetime with your NiMh (so only low discharge-currents) you can be expecting to get FAR over THOUSAND !!!! cycles with a A123-battery! (we have now some selfmade tests with over 1000cycles but on much higher loads..
when we can trust the claims of A123-Systems on a low load like on your bike it should be even several thousands of cycles !!)

very good thing on the A123 is that also when getting older and after many cycles there is only a slow loose of capacity.. (we measured 6% after 400cycles)
and inner restistance is unlike other batteries (Nimh, Lipos) barley increasing at all !!!
the first 100-200cycles the battery even becomes better and better !

at halfe discharged and 35°C cell-temperature we measured ~9mOhm of inner restistance
this value stayed at this low value for the first 500cycles !
which other battery do you know which can do that ?!?

what does that mean in reality:
when you drive your bike lets say 200days a year, every time empying the battery completley,
you will see after 2 years about 6% less possible distance to go (so instead of maybe 20km only 19km
but SAME power as on the beginning !!
here they are differnet to most NiMh and Lipos i have tested..
none of them would show after 400cycles same inner restistance !

 

[JohnInStockie]

@ kraeuterbutter

OK, so let me get this right in my mind. If A123 re-cell my NiMh battery with 8 A123 Fepo in series.....

1) It will be the same weight.
2) It will work the same as a Normal NiMh
3) I will get many many more charge cycles.
4) I will get 16.1Ah (instead of 6.5Ah)
5) It will not damage my controller or my motor??
6) I can use my current charger??

Is that what you are saying? If yes then I obviously have one other question, How Much?

John

 

[kraeuterbutter]

ad 1)
not neccessaraley.. you can make a Fepo4-pack with 6,9Ah with lot less than 4,5kg as well and still more power

ad 2)
what do you mean by that ?

ad 3)
yes, for sure

ad 4)
depends on how many cells you combine

ad 5)
the battery will not function as a natural limit like some week batteries do..
that said:
if you short your motor and it pulls 500Amps !
the battery will deliver that 500A (only going down with voltagae to about 19-20Volt)

a full charged 8s Fepo4 will be at 28,8Volt
a full charged 20cell NiMh (24Volt nominal) will be at 28Volt fresh from charger
(depending on peak-level)
so: motor will not be damaged, and controller.. depends on your controller but most likely: no, will not be damaged

6) of course not

how much:
when you make a pack by yourself:

8s3p with 6,9Ah, more power and around 1,7kg bare-cellweight: ~240$-260$

8s7p with 16,1Ah, more power and around 3,9kg bare-cellweight: ~600$

or a light-weight setup for short distances:
7s2p and slightly less voltage than 24Volt Nicd
(but still ~21Volt at 30A)
with 4,6Ah and only 990g bare-cellweight would be around 140-150US$

this 1kg light pack would still be capable to put out around 1000Watt continousely and over 2000Watt for short

 

[coops]

@ JohnInStockie

Hi John I think what kraeuterbutter means to say in answer to (6) is that, since a A123/FePO4 battery is a type of lithium battery, they need a different charger from a NiMH battery - at least I think that's it?!

@ Kraeuterbutter

Thanks for the update on these new batteries: they do sound promising.

I'm definitely interested if they give some weight, power, charge speed and lifetime advantages over current Li and NiMH in ebike use, with no apparent disadvantages except cost.

Some questions if I may: 10 years life is claimed, but what is currently the longest term use (in time, not cycles) at rates similar to ebikes e.g. 20A max and 36-48V? Also, from your experience, how technically difficult and dangerous is it to try to make an A123/FePO4 cellpack and use it (i.e. should it be made professionally)? and lastly, how quickly could one charge a cellpack like this for ebike use e.g. around 36-48V 10-15Ah min, (1) for best lifetime (2) in case speed-charge is needed and how portable would the charger be (could it be carried on a bike?)?

Apologies if any of this information has been posted elsewhere, I did not find these specifics .

Thanks,

Stuart.

 

[JohnInStockie]

Thanks Coops, I dont really understand this technology too well.

Can anyone advise:-

1) What does 8s7p mean? Does it mean 8 x serial and 7 x parrallel ? Does that mean a total of 8 x 7 = 56 batteries ? So that would be 8 x 3.3V = 26.4V and 7 x 2.3Ah = 16.1Ah Is that right?

2) Which model of battery would this be, the M1?

3) Would these batteries physically fit into a Twist battery case, how big are they?

4) How much are the chargers?

5) Who can advise a non-technical person (such as me) as to how these would need to be assembled, or is there a company that will do it that anyone can recommend?

6) Where can you buy the batteries and the charger from?

And mainly to you manufacturers, have any of you tried these batteries? Are you/ would you consider putting these into your bikes?

From the info given, if I get 16.1AH, that would vbe well about 45 miles per charge for me (and my mass), and about 70 miles a charge for Flecc and other human sized human beings.

That would be market-leading...

John

 

[coops]

I dont really understand this technology too well.

You & me both! Your welcome though, John Though I'd like to enjoy any benefits to be had, I don't think its something to dabble in or undertake without knowing exactly what you're doing: messing with batteries of ebike capacity can be dangerous enough if care is not taken; lithium ones have had a reputation for being moreso!

There is some more discussion of these newer lithium batteries in this thread from about midway through.

Can anyone advise:-

1) What does 8s7p mean? Does it mean 8 x serial and 7 x parrallel ? Does that mean a total of 8 x 7 = 56 batteries ? So that would be 8 x 3.3V = 26.4V and 7 x 2.3Ah = 16.1Ah Is that right?

2) Which model of battery would this be, the M1?

3) Would these batteries physically fit into a Twist battery case, how big are they?

4) How much are the chargers?

5) Who can advise a non-technical person (such as me) as to how these would need to be assembled, or is there a company that will do it that anyone can recommend?

6) Where can you buy the batteries and the charger from?

1) yes 8s7p is short for 8 series 7 parallel and yes 56 cells would be used to make such a 16.1Ah battery like you said: you could make one smaller or bigger; I think the more cells in "parallel", the lower the current draw of a motor per cell, but that doesn't seem too great an issue for these cells so you could quite possibly make much smaller cellpacks than 56!

2) Sorry, I don't remember that one John, rings a bell though...

3) & 5) As has been said, some or all lithium batteries involve more complex setup & charging than NiMH, and recelling or making a cellpack is quite technical by the sounds of it, so what I said above holds. You may well be able to use a Twist case for such a battery, but it would be a task for someone very experienced/professional in electronics etc. . Lets hope if these cells are good for our bikes that somesuch folks start to make such mods & tell us how, eh John

4) & 6) I think there's some info on costs etc. either in this thread or that other one linked above. Kraeuterbutter buys in Europe & mentioned 280 Euros for one battery if I recall, not sure what size, and something like 120 Euros for a charger? Sounds steep I know, but if these batteries can last 10 yrs, work well & can be recharged in minutes not hours, then I'm game!

Flecc said some ebike makers have been trying these sorts of batteries, but I have no more information about conclusions, good or bad.

From the info given, if I get 16.1AH, that would vbe well about 45 miles per charge for me (and my mass), and about 70 miles a charge for Flecc and other human sized human beings.

That would be market-leading...

Probably about 30 miles for me then, John

Stuart.

 

[JohnInStockie]

You may well be able to use a Twist case for such a battery, but it would be a task for someone very experienced/professional in electronics etc. . Lets hope if these cells are good for our bikes that somesuch folks start to make such mods & tell us how, eh John

Absolutely !!! Do you think if we just start posting batteries randomly to Flecc he might just get curious and do it for the fun of it

if these batteries can last 10 yrs, work well & can be recharged in minutes not hours, then I'm game!

not being funny, but count me in!!!

 

[flecc]

No way! I'm a critic of new battery types and the way they are hyped. They are always wonderful until they are tried, and we only have to look at many's Li-ion experiences to see that.

The problem with using cells in parallel is that they cannot be charged like that. Therefore a very complex charging setup is needed which deals with each parallel cell channel separately, while leaving them interconnected for use.

The e-bike companies are trying out the new types all the time, but in practice they rarely deliver. eZee have tried Li-poly for example and have found the results in their words to be "terribly disappointing".

They were also experimenting with Fepo4 several months ago, but still nothing has come to light yet.
.

 

[JohnInStockie]

I must admit this is all very confusing to me. If I were to invest in these batteries then I am either gullable, or shrewd, there is no middle ground.

I suppose if the e-bke compaines experts would explain their reasons for discounting them that would help as if their reason was ONLY cost, then you could buy with relative confidence. If not, then dont buy at all.

I am as keen as the next person to push improved battery technologies, but I cannot afford to waste money either.

john

 

[coops]

Do you think if we just start posting batteries randomly to Flecc he might just get curious and do it for the fun of it

Its worth a try... just make sure all packages are puncture resistant to avoid explosions! You got money burning a hole in your pocket, rather than the li batteries then, eh?!

Only thing is, how long will the tests take to conclude whether they work & last?

The reason I've stuck with NiMH so far is my lack of confidence in Li durability: if I'm to pay a hefty premium for Li, I want to know they have practical advantages (weight, charge time, power supply, no depth of discharge issues, no resting discharge, recycleable (?) and better useful lifetime). All I've heard from Li so far, other than these newer ones, is possible rapid capacity decrease over 1-2 yrs, used or not, accelerated degradation if battery is often near fully discharged, and some problems with power cut-outs on heavy demand: this poorer utility & shorter life for much more than NiMH prices and not much weight saving or performance gain?!

I hope that info is wrong & Li are more durable for ebikes, but that's one question only time can tell.

 

[coops]

I'm slow posting today, just seen the last 3 posts after writing my last reply!

I'm a critic of new battery types and the way they are hyped

Absolutely, we need clear & real results, not hype. E.g. 10 years lifetime claim - all very well, but would the maker give a guarantee for even 5 years if they're confident? After all, if high discharge rates, high depth of discharge, recharge speed & current etc. don't greatly affect long-term performance, and cells remain well-balanced even if charged/used in parallel, then why not give a guarantee? Short of piercing the cells, I don't see how they could be seriously damaged under normal use??

If they were guaranteed like that, and there was consumer evidence to show they have such durability, I might give it a try

P.S. The undesired occasional "side-effects" of Li and some of their apparent peculiarities & complexities still worry me somewhat, as to whether they can ever be considered reliable & safe... especially in ebike type capacities.

 

[kraeuterbutter]

charger:
yes, a charger for Nicd or NiMh will not work..
but charging itself is easier than with Nicd/Nimh cells (no delta-peak-measuring needed)
there are peple charging them with notebook-powersupplies, or
regulated power supplies which many people already have at home for hobby-purposes

chargetime: when you can manage to charge with 10C, the cells are fully charged in 5min..
a friend of mine charges a 4cell-pack from his 12V-car-battery with a homebuild charger (~20-25$ for the parts) he made himself..
chargecurrent: 26A
the batts are full after around 5min charging and get 40°C warm during charging which is ok..
a A123-technischan said to us, that with that chargecurrent he will not see 1000cycles.. (but maybe 300-500 )
thats said for charging

Some questions if I may: 10 years life is claimed, but what is currently the longest term use (in time, not cycles) at rates similar to ebikes e.g. 20A max and 36-48V?

well, the batts are not that long on the market that we can say that excactly..
fact is: its about 1year we have that cells now in our community and the oldest (1year old) work same as the new ones

A123 Systems says:

A123’s Nanophosphate™ technology delivers exceptional calendar and cycle life. At low rates our ANR26650M1 cells can deliver thousands and thousands of cycles at 100% Depth-of-Discharge, a feat unmatched by commercial lithium ion cells. Even when cycled at 10C discharge rates, our cells deliver in excess of 1,000 full depth-of-discharge cycles.

other manufactor say: 6years for NiMh, and 3-4years for Lipos
when you take this in account i think we can be sure that the cells life more than 6years (something only Nicd realy manage good, but they are toxic and low capacity)

lets say it this way: all tests sofar we made (overcharging for several HUNDRET ! cycles, deepdischarging, charging the cells in hot condition wihtout cooling down, ...
all this things are things, which killed Lipos very fast (sometimes in only 1 cycle !!).. and the A123 do survive such abuse

Also, from your experience, how technically difficult and dangerous is it to try to make an A123/FePO4 cellpack and use it

i solder the packs with 80Watt solder-iron
when you use a big,heavy solder-spike soldering is done in ~2seconds and the cells do get only barley warm..
A123 systems say, you should not solder the cells, because the heat destroeys the electrolyt inside..
but fact is: they sell "developer-packs" with solder taps on the cells for higher price..
we buy our cells at ebay (Dewalt-packs), disassable them and build our own packs and safe up to 50% money
we have not noticed shorter cell-life doing this (but we also have to say, that only few of us have managed to make more than 400cycles during this one year with our cells so far)
and: Sanyo or Panasonic also say in there specification, that it is not allowed to solder there nimh and Nicd-cells ==> and we do it for 25years now without problems

for using it: i use it in my helis of mine..
for example:
30A average current,
100A peaks..
and thats with a 1p pack !! (so the current of the motor is not divided by the count of parallel cells ! the complete load goes to the single cells)

i charge them up to 10times a day with 8A current (my charger can not more)
-> that means:
empty the cells in 4-5min
charge them immediatly without cooling in 16-17min
that works very good... (i would not want to treat normal Lipos that way *lol*)

and lastly, how quickly could one charge a cellpack like this for ebike use e.g. around 36-48V 10-15Ah min, (1) for best lifetime (2) in case speed-charge is needed and how portable would the charger be (could it be carried on a bike?)?

best lifetime: A123-Racing says: 4C charge, 10C discharge: over 1000cycles
fast charge: up to 10C is possible -> that are 5min charigng time (after 5min the batts are about 90% full)

charger: depends on how strong the charger should be.. the problem is:
when you want to charge a 16Ah-pack fast, you would need very high charge-power..
but even when you only want normal chargetime (1hour charge) 16A chargecurrent would be needed !
so: the big problem is the transformator.. but the same transformator is needed for a nimh-charger as well..
so size and weight should not differ at all
procedure of charging (technically) is easier than on nicd/nimh as said

@JohniStockie:
yes, the M1 cells iam speaking about.. don´t have experiences with the others.. even don´t know if you can get thouse cells a s a private person

for your "i want most drivable distance"
if you want the most capacity for weight the A123 are not ideal..
there "normal" lipos are better..
for example Thunder Power 2000 Prolite..

7s15p -> that would be 3,7 * 7 = 25,9V nominal and 30Ah
at around 4,1kg (without case)

so nearly twice as much capacity at same weight

disadvantage: after ~3 years the cells die, inner restistance goes up
single-cell-protection is neccessary
if something goes wrong this cells can burn
discharged too deep or overcharged (overcharging normaly with right charger and balancer can not happen) will ruin the batts immediatly
and last: the price... a 7s15p would cost 1500Euro
i use this cells for heli were i need most power at lowest weight and long flying-time...
but for 90% of my applications i meanwhile like A123 more..
+ no risk of fire
+ easier handling, more robust, robust case
+ and they will not die after 3years like my thunderpower do currently
+ can drive the same heli with same power (but only halfe of flyingtime) for 1/4 price of the thunderpower-cells !

As has been said, some or all lithium batteries involve more complex setup & charging than NiMH, and recelling or making a cellpack is quite technical by the sounds of it, so what I said above holds.

thats in my eyes not realy true..
or let say: from technical stand-points..
charging a lipo-cell is much more easy than charging a nicd or Nimh (which needs a delta peak sofistic ship inside, or some reflex-charging method to avoid memory-effect or/and lazzy battery-effect)
charging a lipo for that is very easy, building a charger by yourself (if you are good in electroncs) easier than building a nicd/nimh charger

its important to hold Lipos at same level, so not some cells are overcharged (which would ruin this cells or even make them start burning)

(Example: Lipos are allowed to charged to 4,23Volt per cell
you have a 10s pack
so the charger would stop at 42,3Volt
now: one cell is higher in voltage because of inbalance..
9cells are at 4,15Volt/cell -> that are 9*4,15 = 37,35Volt
so the one last cell will have 4,95Volt
this would ruin this cell
to avoid that a balancer is needed (single-cell charging, or build in in the charger.. or a external balancer you use during charging which can be bought for 35euro)

the Fepo4 are not that critical on that purpose..
it would be enough to look every 100cyles if they are still in balance..
if not, you charge each section of paralleled cells sepeartly.. (so in reality maybe once a year in ebike-situation)

for buying the cells:
in europe i pay 15,5euro per cell..
i buy them in the US.. with shipping to europe i come to around 10US$ per cell

last an maybe important:
do i think, that this cells are for everybody in the moment..
fromt he qualities of the cells: YES of course..

but there are problems:
do you get a package a non electrical person can implement immediatly in there bikes.. -> no

i see this cells for people who are not buying a complete bike and are satisfied the way it works..
i see this cells for people who build there own bike or make a conversion, who can solder... if this people use this cells, they get a cell-pack which will outperforme any lipo or nimh-cell for ebikes you can buy in the moment

the A123 is used for several electric cars meanwhile.. also some people convert the toyota prius to use this cells..
the world fastes electric motorcycle, the Killabike -

here you can see what is possible with this very same cells:
KillaCycle - World’s Quickest Electric Motorcycle
the killa-bike... world fastes electric motor-cycles..

from a 73kg A123-systems-pack they get
260kW (= 260000Watt) of power, over 350hp

this said: you don´t need to parallel the cells in e ebike for power-reason..
even a 8s1p pack (= only around 570g light) would power Johns bike easily..
(800Watt continously, 1800Watt short)

you have to parallel the cells, because with only 2,3Ah for a single cell drivetime would be not that great..

with the 2C lipos many bikeshops cell paralleling (they are often paralleled inside you - as user - don´t see or know)
and making large packs is not only needed and done to get long drivedistances but also because otherwise the weak 2C lipos would be not able to deliver enough power (~for example 30A) for the motor

well.. so much written.. hope there is nobody upset about this..

 

[kraeuterbutter]

for soldering here are some description how to do it with lot of pictures:

soldering SIDE-by-SIDE:
How To Build a Battery Pack from A123 Cells - RC Groups
(English description)

soldering INLINE:
Lomcovak.czilna:A123 za sebou
(not english but lot of speaking-for-themselfe pictures)

and here also a good description with lot of pictures:
Dissecting DeWalt 36V Packs (A123 Systems)

for people which have already used a solder-iron sometime its no problem building a pack

last: i excuse for my bad English.. i have written that much that i did´t find the time to re-read it combined with dictonary

 

[kraeuterbutter]

oh.. last thing: on the soldering descriptions it says: that the point in the middle of the cells is a safety vent and should not be over-soldered

thats not true.. it turned out, that this is the point were the electrolyt was filled in.. so it can be oversoldered without any danger or risk..

 

[flecc]

Not at all kraeuterbutter, post as you need to make your point, we appreciate your contributions.

Like you, I've soldered directly onto NiMh cells, and many other types, for years without any ill effect, the secret being speed of course, using plenty of heat quickly, not minimal heat prolongued.
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