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Brammofan
07 December 2010, 0852
I'm pretty clueless about electricity, so I need some help. I was over on a gas bike forum and they were talking about Brammo bikes specifically and electric bikes in general and, as usual, dissing the range.

I mentioned the Enertia (40 mile range) and the Enertia Plus (80 mile range) and noted that the bikes, as reported, weighed the same. Sure, some components might have changed weight, but I made the assumption that the energy density of the batteries had doubled and this was not unlike Moore's law (transistor # per card doubling every two years).

One guy said:
unlike Moore's law, the energy density in commercially viable batteries hasn't gone up by even a single order of magnitude in 100 years. There are physical constraints that have proved challenging for as long as people have been at this, and while there is always hope for improvement, huge improvements have proved to be much harder than just about anyone would have imagined 5, 15, or even 50 years ago.

So I said,
It might depend on your definition of "commercially viable" but are you saying that a Lithium Ion battery from 2010 doesn't have at least twice the energy density of a lead acid battery of the same size from 1910?

and he replied,
To be raised an order of magnitude higher it must be at least the same amount squared... not just doubled. "Amount of what?" I dunno, some smaller capacity measurement that doesn't total to "1" or "2" in said LA battery.

It's just a friendly debate - but I'm out of my league here and wondered if anyone had any facts/figures that disputed his hypothesis.

lugnut
07 December 2010, 0908
It's just a friendly debate - but I'm out of my league here and wondered if anyone had any facts/figures that disputed his hypothesis.

I don't have energy density figures at hand. But order of magnitude means by a factor of ten, maybe plus or minus a couple. Do we have batteries 10 times as energy dense? Don't know. You should have asked him if he has gasoline which could get him 10 times further per gallon.

frodus
07 December 2010, 0919
I'm gonna crosspost this because its relevant..... the density argument on endless-sphere:
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=7458&start=0&st=0&sk=t&sd=a

Looks like SLA is in the neighborhood of 50wh/kg and Lithium Ion is like 150wh/kg (not all, just some. Lifepo4 is still under 130wh/kg as far as I know). Thats still 3x (which is huge for us, but not enough realistically for everyone). Gasoline is 12.7kwh/kg. So He's right.... kinda. Because you no longer need a huge engine, gas tank, exhaust and all of the support mechanicals and you also have 3-4 times the efficiency in electric than you do in a gasoline powered engine. So you're really only looking at what, 2540wh/kg...... but thats still 50 times the energy in SLA....

Brammofan
07 December 2010, 0925
I knew I could count on you, Travis. Thanks.

chef
07 December 2010, 0933
Some of the more exotic chemistries might be close to achieving 10x the density of lead. Do you know what the Enertia Plus uses? Odd that he would think an order of magnitude is squared. Maybe he was thinking in base 2, but colloquially order of magnitude is always (AFAIK) base 10. Even in base 2, it's not the value squared, it's 2x, 4x, etc.

It should be a straight-forward exercise to look up the energy density of a given chemistry. I think I've seen figures in Wh per unit mass.

chef
07 December 2010, 1002
Was too slow composing, Travis beat me to it :)

Looking through Wikipedia, there are two measurements of density: specific energy (Wh/kg) and energy density (Wh/L). The latter takes into account the physical density of the battery material.
Rooting around the web turned up a Nexergy document -
http://www.nexergy.com/media/pdfs/batterychemchart.pdf

Rechargeable lithium ion has 5x the energy density of lead. Lithium thionyl chloride goes all the way up to 10x. It's not rechargeable though so not very useful for EV applications.

I learn sumthin new every day...

frodus
07 December 2010, 1017
even then though, SLA is about 50wh/kg..... and I haven't seen anything much over 200wh/kg.

Maybe if we're talking the worst and cheapest SLA compared to the absolute best achieved in the lab.....

lugnut
07 December 2010, 1113
even then though, SLA is about 50wh/kg......

I wonder what it was 100 years ago????

chef
07 December 2010, 1210
even then though, SLA is about 50wh/kg..... and I haven't seen anything much over 200wh/kg.Specific energy (Wh/kg) vs energy density

Tony Coiro
07 December 2010, 1222
Haha, chef, I hate it when I start thinking in base 2. But yea, order of magnitude is 10X.

frodus
07 December 2010, 1246
Specific energy (Wh/kg) vs energy density

I was just referencing numbers they used in that thread...... but, since you want to pick ;)

It's still energy density, because the energy is stored in the chemicals and components of the battery, which have a certain density. So the energy stored in them, per unit of weight can be converted to unit of volume. It's still relating to the energy per given unit of measure, whether its weight or volume. In most cases, you get a Wh figure (calculated with Ah and V) and a weight figure along with a volume figure. You can calculate either Wh/kg or Wh/liter, both are important, since you only have so much room and usually a weight limit.

Brammofan
07 December 2010, 1312
I was just referencing numbers they used in that thread...... but, since you want to pick ;)

Damn. I knew this was going to happen.

Dudes. This is why you all still live in your mothers' basements. ;)

DaveAK
07 December 2010, 1405
LOL

(message too short? :()

chef
07 December 2010, 1541
I was just referencing numbers they used in that thread...... but, since you want to pick ;)

It's still energy density, because the energy is stored in the chemicals and components of the battery, which have a certain density. So the energy stored in them, per unit of weight can be converted to unit of volume. It's still relating to the energy per given unit of measure, whether its weight or volume. In most
Just passing along the definitions. Specific energy and energy density have well defined mathematical definitions. If you choose to ignore them or redefine them, whatever.

I think there should be a combined figure including both mass & volume, something like Wh/kgL. That would make very explicit the density of the cell.

frodus
07 December 2010, 1557
yeah, oh, I agree, they are ignored.... but with the stuff I do, I kinda gotta go with the manufacturers and consumers....

I know what you're saying though....

Richard230
07 December 2010, 1610
Here is an item that would seem to fit into this thread: According to Bloomberg News, U.S. Energy Secretary Steven Chu says that "the development of an electric car battery able to compete with the internal combustion engine may be five years away". "The storage capacity of current electric car batteries needs to be increased by a factor of six or seven times in order to be acceptable to car drivers", according to Mr. Chu. He goes on to say that "battery life needs to be extended to 15 years and the cost needs to be reduced by a factor of three". Mr. Chu made these statements in a speech in Cancun, Mexico, where the UN climate envoys from 193 nations are holding global warming treaty talks.

So does Chu know what he is talking about, or is he just adding to the global warming problem? :D

DaveAK
07 December 2010, 1615
Higher capacity, longer life and reduced cost would all be attractive to the consumer, and I think the targets he mentioned are reasonable ones to get people on board the EV wagon. Now, whether they are attainable in five years ........

(Oh, and the last two kinda go hand in hand as far as overall cost of vehicle ownership is concerned.)

Warren
07 December 2010, 2127
chef,

"Do you know what the Enertia Plus uses?"

This was asked over on this thread.

http://www.elmoto.net/showthread.php?658-Videos-of-the-Empulse-RR-put-up-by-Brian&p=4774&viewfull=1#post4774

Still waiting to hear.

Warren

jazclrint
07 December 2010, 2359
Well, having just checked out the spec's on the Brammo site I'd say they are LiPo. The Enertia has LiFePo4 and stated 2000 charge cycles. Where as the Plus's battery pack is only rated to 500 charge cycles. I am not sure how I fell about that. I would much rather have LiFePo4 batteries in a street bike. But what can you do. Beggars can't be choosers.

How about the argument that, if you accept the DOT's defintion that 1 gal of gas equals 33.7kWh, these bikes are getting anywhere from 220 to 440 miles per gallon, with over 300 mph in real world conditions. Not to mention at my house I could fill and empty Enertia for $.29, and a Plus for $.56. A "gallon" of electricity costs about $3.05 at my house, while regular is $3.11 right now.

teddillard
08 December 2010, 0438
I would much rather have LiFePo4 batteries in a street bike.

Would you really? Lemmee see, I hope I have this right, but at 1/2 the weight of and 1/3 the space for the same specs*, you're sure? Not to mention an astronomical discharge rate...

Now, sure, LiPo is touchy. You have to be very careful about your DOD, or bad things can happen very dramatically. But work with me here. You're running a pack with the same weight but twice the capacity, then the chances of running it down are less right?

If you want to get a crash course on LiPo, the ES thread is probably a good place to start:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=19956

I happen to know of a pack being built right at the moment that's gonna blow your socks off... ;)

*confirmed, for capacity anyway. Compare this (http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=14845) with this (http://www.batteryspace.com/lifepo4rechargeablecellcr123battery30v450mah135wh1 pc.aspx).

billmi
08 December 2010, 0625
Would you really? Lemmee see, I hope I have this right, but at 1/2 the weight of and 1/3 the space for the same specs*, you're sure?

Performance wise on the bike - with the improved energy density, sure the LiPos are great. Economically though, they don't look so good when they cost similar per KWh to LiFePo4 prismatics but have 1/4 to 1/6 the lifespan.

teddillard
08 December 2010, 0701
Performance wise on the bike - with the improved energy density, sure the LiPos are great. Economically though, they don't look so good when they cost similar per KWh to LiFePo4 prismatics but have 1/4 to 1/6 the lifespan.

I believe they're actually slightly cheaper... but point taken. It's a tradeoff I think a lot of people are willing to make at this point. I certainly am. :D I kind of thought Rich would be too, what with all the ICE vs electric discussion in the past.

Warren
08 December 2010, 0708
The top TTXGP guys, running the best LiFePo4, were still hugely heavy beasts. Look at the weight of the eRoehr bikes to get the idea. The smart way to improve speed and range is aerodynamics. Craig Vetter, Royce Creasey, Cedric Lynch, Arnold Wagner, and many others figured this out long ago. But it appears, even with the pathetic energy density of batteries, most will continue using the "get a bigger hammer" approach.

Warren

teddillard
08 December 2010, 0731
The top TTXGP guys, running the best LiFePo4, were still hugely heavy beasts. Look at the weight of the eRoehr bikes to get the idea.

(right, which is why LiPo, at half the weight, is my option... :D)

Richard230
08 December 2010, 0839
Scottie, I need more power. But Captain, I think she's going to blow. :D

Getting back to energy density for a moment, I though that the statement by Mr. Chu that energy density could be improved by six or seven times within a period of only five years seemed very optimistic to me. I don't think there is an equivalent to Moore's Law for battery technology advancements. It takes a lot longer (compared to advancing computer processing power) to dream up new battery designs, make sure that they actually work in the real world and are safe, develop something that is not going to pollute the environment, design and build factories to produce them (to say nothing of finding funds to build the factories) and for EV manufacturers to design and build vehicles that can use these batteries. But then this was a government official who was speculating about this time frame and we all know that government officials live in a make-believe dream world. :rolleyes: Am I right or wrong?

DaveAK
08 December 2010, 0929
The top TTXGP guys, running the best LiFePo4, were still hugely heavy beasts. Look at the weight of the eRoehr bikes to get the idea. The smart way to improve speed and range is aerodynamics. Craig Vetter, Royce Creasey, Cedric Lynch, Arnold Wagner, and many others figured this out long ago. But it appears, even with the pathetic energy density of batteries, most will continue using the "get a bigger hammer" approach.

Warren
Personally I think the whole aerodynamics argument is exactly the same as the battery chemistry one. It's not a question of bigger hammers, it's a question of what hammer you've got and what hammer you can afford. I have no doubt that I could make a LiPo brick that would outperform a steam powered streamliner, or I could have a LiPo streamliner. As it happens I have neither.

Undoubtedly LiPo can give better performance than LiFePO4, and a more aerodynamically efficient vehicle is better than a bus, but they aren't the only considerations.

frodus
08 December 2010, 0929
hmmm, i got curious so I searched the newsfeeds for "battery density" and found this:
http://pubs.acs.org/cen/science/88/8847sci1.html


Winfried W. Wilcke makes the case for lithium’s favorable energetics by noting that oxidizing the pure metal releases nearly 11,700 watt-hours/kg. That value is quite close to the value for one of the most energy-dense common liquids—gasoline.

Wilcke, who is a program director at IBM’s Almaden Research Center, in San Jose, Calif., goes on to explain that because of engine inefficiencies and other real-world constraints, only a fraction of gasoline’s energy can be put to practical use in an ordinary automobile. The same is true for Li-air cells because of structural materials and other battery components that add weight but don’t provide energy.

“Lithium-air is a battery technology that’s extremely high risk, but one that’s also potentially extremely high gain.”It turns out that the practical energy density by weight for gasoline and Li-air cells, according to Wilcke, is only about 1,700 Wh/kg. But that value is still many times higher than that of nearly every other battery system, including today’s best Li-ion batteries, he says. That advantage, which could be as high as a 10-fold increase in energy density relative to Li-ion batteries, in principle should translate to a 10-fold enhancement in driving range with no increase in battery weight. But designing a practical Li-air electric-vehicle battery that can pack that much energy per weight “is a tremendously tough goal” that’s beset with technical challenges, Wilcke acknowledges.


but then he goes on to tell about how inefficient they can be, and how low discharge rate they can be.



But there are plenty more articles from universities and researchers that have found much higher density and high discharge rate battery chemistries..... but they're not yet commercialized. So its only a matter of time.

methinks we should all go do some reading :)

jazclrint
08 December 2010, 1434
Would you really? Lemmee see, I hope I have this right, but at 1/2 the weight of and 1/3 the space for the same specs*, you're sure? Not to mention an astronomical discharge rate...

Now, sure, LiPo is touchy. You have to be very careful about your DOD, or bad things can happen very dramatically. But work with me here. You're running a pack with the same weight but twice the capacity, then the chances of running it down are less right?

If you want to get a crash course on LiPo, the ES thread is probably a good place to start:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=19956

I happen to know of a pack being built right at the moment that's gonna blow your socks off... ;)

*confirmed, for capacity anyway. Compare this (http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=14845) with this (http://www.batteryspace.com/lifepo4rechargeablecellcr123battery30v450mah135wh1 pc.aspx).

Yes, but note I said street bike. Many of our conversations center around racing. LiFePo4 for a street bike because they are stable, 4 times the life cycles, and consistent with power over their entire life, which makes them predictable. A street bike is about fun, but also convenience and practicality. You don't ride a GSX-R1000 AMA Superbike on the street. It is completely impractical. The gearing is all off, the power is peaky, the clutch won't hold up to stop and go traffic, the geometry would try to kill you on lose surfaces and around town, ect, ect. Also, the idea of having to replace a battery pack in (just for example) a Enertia Plus every 30,000 miles, and having the performance degrade to that of a regular Enertia by what, 20,000 to 25,000 miles (?) is not a cool thought. My father is looking at getting a small motorcycle for commuting the 30 mile one way trip. I was trying to lean him to an Enertia because of the operating costs, then the Plus came out and I thought that would be the ticket. But seeing that the life cycles are so low, it just can't compete with a $4000 Ninja 250 as far as cost benefit and convenience. He works in the maintenance dept of a state University, and I'm not sure he could get away with plugging it in at work. He wouldn't have to if he had a Plus, but with as much as temps vary here, and as unpredictable as LiPos seem to be, I wouldn't feel comfortable recommending it. I now look at the Plus more as urban commuter that can now handle the occasional freeway blast and out of the way errand runner than the consistent 60 mile commuter I had thought of it before. But that is ok, because it suits a lot of consumers out there, just not the 30 mile one-wayers up here in the sticks.

But I digress. Now, race bikes are a WHOLE other thing. When I picture building a race bike practicality goes right out the door. It's all about performance. You use the thing that could blow up any second because its faster, lighter, and more powerful. For me LiPos would be the only choice for a race bike, or maybe those Li-Air batteries. Who cares if you blow up on a race track as long as you're going fast while doing it. :D

But, it seems LiFePo4 technology is making progress isn't it? Here's a chart comparing chemistries, http://www.batteryspace.com/li-ionsinglecell.aspx . According to this, LiFePo4 is cheaper than SLA over the life of the battery. This light project of mine has been good for studying batteries.

Here's some numbers from batteryspace.com. Now I am comparing the same sized 26650 cells (a long C-cell, or so I've read) LiFePo4 with LiMnNi (one form of LiPo). So they are the same size, and the same weight at 3.2 oz (90 grams).

LiFePo4 3.2v 3.3Ah 16.5A rate 10Wh 117.33 Wh/kg $8.95 on sale
LiMnNi 3.7v 4Ah 10A rate 14Wh 163.17 Wh/kg $10.95 on sale

So, these 2 cells are the same size and weight, but the LiMnNi had more power. Is this new tech?, blatant lying?, because this isn't the twice as big, nor a 1/3 heavier I had read elsewhere as well as here. But they are only 75% as powerful. That I can deal with for a street bike.

P.S. Any word on nano tube technology?

jazclrint
08 December 2010, 1444
OK, here's a random thought. What would we all do with 168 kWh (the equivalent of 5 gallons of gas)? And in the size of a 5 gallon gas tank!? There wouldn't be a ICE on the planet that could keep up. Honda would show up with one at next year's MotoGP, and crush everyone. :D

teddillard
08 December 2010, 1507
Oh c'mon now... it's not all that complicated, and the Enertia + and the Empluse are great examples of streetable higher performance, and yes I'm guessing, like you, we're looking at LiPo there. (Where do you get that LiMnNi is a "form of LiPo"? http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery)

My decision: I'm building a bike. I want to go as fast as possible, street or otherwise. My conclusion? LiPo. See how simple that is? :D

DaveAK
08 December 2010, 1510
Oh c'mon now... it's not all that complicated, and the Enertia + and the Empluse are great examples of streetable higher performance, and yes I'm guessing, like you, we're looking at LiPo there. (Where do you get that LiMnNi is a "form of LiPo"? http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery)

My decision: I'm building a bike. I want to go as fast as possible, street or otherwise. My conclusion? LiPo. See how simple that is? :D
Don't forget to streamline it!

teddillard
08 December 2010, 1521
Don't forget to streamline it!

And cover the yummy bits? NEVER! :D

DaveAK
08 December 2010, 1525
And cover the yummy bits? NEVER! :D
But you want to go as fast as possible. Gotta streamline it. :)

Warren
08 December 2010, 1547
Folks,

Announcements like this one are coming out every week.

http://electric-vehicles-cars-bikes.blogspot.com/2010/12/toyota-announces-4-layer-all-solid.html

I think Brammo's strategy is smart. Build a bike that comes as close to ICE performance as current technology allows period. Unless you live in San Diego, you won't be riding your bike every day. Most places you won't be riding more than half the days in a year. Most don't have a 55 mile round trip commute, like mine. Those cells will last 3 years for most people. By then, much better cells will be available. If you had half used up LiFePo4 in there, you'd be looking for a way to dump them and buy the new stuff anyway.

Warren

jazclrint
08 December 2010, 1552
(Where do you get that LiMnNi is a "form of LiPo"? http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery)

From the battery space website, from what I had read on wiki 2 weeks ago, and from the definition of polymer. http://dictionary.reference.com/browse/Polymer

I believe, really, LiFePo could also fit under the generic polymer title, but it acts so differently that people choose to not use that generic term.

jazclrint
08 December 2010, 1554
My decision: I'm building a bike. I want to go as fast as possible, street or otherwise. My conclusion? LiPo. See how simple that is? :D

And this is why I will always be faster than you. :D

teddillard
08 December 2010, 1645
And this is why I will always be faster than you. :D

Uh, you need an actual bike to do that, dontcha? lmao!

jazclrint
08 December 2010, 2039
Uh, you need an actual bike to do that, dontcha? lmao!

Yeah I still haven't heard from the state police if they have found the 2 500s and the parts to my VFR.

teddillard
09 December 2010, 0131
Yeah I still haven't heard from the state police if they have found the 2 500s and the parts to my VFR.
?
I meant electric... but sorry to hear that. Start a new thread here with an alert. Those are a popular build bike and if they're being parted out on CL we'll see them.

Brammofan
09 December 2010, 0808
Speaking of energy density, anyone want some batteries?
Valence - Lithium Ion 12V battery (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260705372627#ht_715wt_1135) -
"Great battery for EVs of any kind. MSRP > $550"
Now on ebay for the buy it now price of $330 and the "make offer" option. It says "more than 10 are available".

More specs:

Integrated Battery Management System (BMS Controller not Included)

Chemisty: LiFeMnPO4

Voltage: 12.8 VDC

Capacity (c/5, 23C): 40 Amp-Hr

Dimensions (Incl Terminals): 197x130x182 mm

Terminals (Tapped Hole): -20

Specific Energy: 79 Wh/kg

Max Continuous Current: 80A

Max 30 Sec Pulse: 120A

Cut-off Voltage: 10 VDC

Charge Voltage: 14.6 VDC

Float Voltage: 13.8 VDC

Max Charge Current: 20A

Internal Resistance (max): 15 mOhm

MSRP is near $600.00 PER UNIT.

Some random guy with the user name "cbramscher" is selling them.

Warren
14 December 2010, 1033
Folks,

I just noticed that the second place bike in the TTXGP finals in Spain, CRP, was running Lipo batteries...92,5 volts, 53kg, 7,4Kwh.

Got me wondering, with all the concern about the short cycle life of Lipo, how many of you have actually run a bike with LiFePo4 for 1000 cycles, even 500 cycles without a cell failure?

Warren

Richard230
14 December 2010, 1459
My 50 Ah Hi Power LiFePo4 cells lasted for about 75 charges before some of them started to fail. About that time the master 4-cell Modalis BMS board blew up. I don't know which came first, the chicken or the egg. The batteries were exposed to a lot of 3.5 C demand during this time.

I still recall how my 1986 Honda VFR 700's battery and VR lasted for 8 years before the original battery finally failed, without me noticing, which then took out the VR. The bike has had electrical charging problems ever since - which were finally solved by installing two VRs in parallel.

Warren
14 December 2010, 1527
Richard,

My point exactly! I'm betting most LiFePo4 cells, run on motorcycles, get cooked from some sort of high C abuse long before their theoretical cycle life is reached. With a professionally built controller/BMS/charger system a Lipo pack might last longer than anybody's home-brewed rig. Well...certainly anything I would come up with.

Warren

DaveAK
14 December 2010, 1542
Richard,

My point exactly! I'm betting most LiFePo4 cells, run on motorcycles, get cooked from some sort of high C abuse long before their theoretical cycle life is reached. With a professionally built controller/BMS/charger system a Lipo pack might last longer than anybody's home-brewed rig. Well...certainly anything I would come up with.

Warren
Well yes, but wouldn't a professionally built LiFePO4 pack last longer than a LiPo one? Not sure exctaly what your point is unless you compare like with like. Use them and abuse them or treat them with care and have them live a long life.

chef
14 December 2010, 1546
To richard's credit, his battery/bms/controller setup was misconfigured. I think there are other elmotos that have had many more cycles. What's the longest running GPR-S 'round here?

jazclrint
14 December 2010, 1550
Richard,

My point exactly! I'm betting most LiFePo4 cells, run on motorcycles, get cooked from some sort of high C abuse long before their theoretical cycle life is reached. With a professionally built controller/BMS/charger system a Lipo pack might last longer than anybody's home-brewed rig. Well...certainly anything I would come up with.

Warren

Obviously I can't know for sure, but this just doesn't sound quite right. I mean, according to Brammo 500 charge cycles should be good for 30,000 miles. Has anyone even approached that, much less 1000 charge cycles. Also, LiPo is said, according to one site that sells them, to have a much worse shelf life, and it's not long before they are performing to less than a level of LiFePo. You may have something about the discharge rate. a quote from Manzinita's webpage for the Headway 10AHr cells,

"Max Continuous Discharge……………………………100A (10C-rate)

Peak Discharge……………………………150A (15C-rate)

Maximum Charge Current……………………………60A (6C-rate)

Cycle Life……………………………1500 @ 1C to 100% Depth of Discharge

Cycle Life……………………………2000 @ 1C to 80% Depth of Discharge"

And then that raises another question for me. Since we run through a controller , and it limits the max amps to the motor, is there a C rating that there is just no need for. In that the batteries could unleash way more power than is going to get put to the motor any way. Is there a way to calculate that?

But, for someone who has to park his bike over a long winter, LiFePo still seems the best bet to me. From what I read about the chemistries on wikipedia (grain of salt) it doesn't seem possible LiPo could last longer than LFP. But only the real world can really tell you. Anyone with real world on this specific thing? What did folks observe at the TTXGP?

frodus
14 December 2010, 1627
And then that raises another question for me. Since we run through a controller , and it limits the max amps to the motor, is there a C rating that there is just no need for. In that the batteries could unleash way more power than is going to get put to the motor any way. Is there a way to calculate that?



I've got 10Ah headways that could potentially do 15C peaks if they were allowed (wouldn't be good for them though), but I designed the pack (so far) for 32s6p. If they did 150A each (15C), that's what, 900A total? But the actual peak on the batteries could only ever be 550A (limit of controller). That would be ~92A each battery, or 9C. I calculated the power needed to push the bike along at 45mph, and its ~60A at ~100V. So that'd only be 1-2C each battery during normal use. Not much need for me to have a higher discharge than about 5C for most of my riding, but this time, my batteries will NOT be the weak spot..... last time those UPS batteries struggled.

jazclrint
14 December 2010, 2243
I'm gonna crosspost this because its relevant..... the density argument on endless-sphere:
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=7458&start=0&st=0&sk=t&sd=a

Looks like SLA is in the neighborhood of 50wh/kg and Lithium Ion is like 150wh/kg (not all, just some. Lifepo4 is still under 130wh/kg as far as I know). Thats still 3x (which is huge for us, but not enough realistically for everyone). Gasoline is 12.7kwh/kg. So He's right.... kinda. Because you no longer need a huge engine, gas tank, exhaust and all of the support mechanicals and you also have 3-4 times the efficiency in electric than you do in a gasoline powered engine. So you're really only looking at what, 2540wh/kg...... but thats still 50 times the energy in SLA....

Travis, having dug around for some numbers it seems to me that electric motorcycles are actually getting 300 mpg(e), where cars are getting 100 to 150 mpg(e). So while cars are 3 to 4 times as efficient as ICE cars, I would argue that electric motorcycles are actually 6 to 9 times as efficient as ICE motorcycles. What is you opinion on that?

Quick math says 847 to 1270 wh/kg for elmotos, no? That's less than 10 fold. That means we're a tobacco virus or Toyota breakthrough away from being on par, or at least almost on par with ICE bikes.

jazclrint
14 December 2010, 2255
I've got 10Ah headways that could potentially do 15C peaks if they were allowed (wouldn't be good for them though), but I designed the pack (so far) for 32s6p. If they did 150A each (15C), that's what, 900A total? But the actual peak on the batteries could only ever be 550A (limit of controller). That would be ~92A each battery, or 9C. I calculated the power needed to push the bike along at 45mph, and its ~60A at ~100V. So that'd only be 1-2C each battery during normal use. Not much need for me to have a higher discharge than about 5C for most of my riding, but this time, my batteries will NOT be the weak spot..... last time those UPS batteries struggled.

Thank you. I thought that might be how the numbers get added, but I didn't know for sure. I'm feeling a bit clever at the moment. :D

Now here's a question. In the world of racing bikes, is getting more amps through the controller and having the motor hold up to it, where the hotrodding side of things comes in? But for my racebike in my head, I now know I have no need for 35C discharge rates. How many amps are the bikes in the TTXGP putting to their bikes?

Also, when I started crunching numbers for my eVFR in my head, I was using Headway batts. Right after the batteries have been charged, the voltage is rated at 3.65v on the spec. Are you not concerned about over volting your controller and motor? I believe you are running an AC20 motor with matching controller, right?

Thank you,
Rich

Richard230
15 December 2010, 0850
My batteries are currently being analyzed by robotic equipment :cool:. Results to follow. See photos below.

Nuts & Volts
15 December 2010, 0932
The advantage of a higher C rated battery is that this means the internal resistance is lower which in term means a longer cycle life.
ie a 35C Lipo 5ah battery being run at 10C will last longer (degrade slower) than a 20C Lipo 5ah battery at the same 10C

Kyle

billmi
15 December 2010, 1102
My batteries are currently being analyzed by robotic equipment :cool:. Results to follow. See photos below.



639

That's a very cool test set-up! I had to really look at the details to see the whole robotic setup, I was so focused on the computer at first glance.

IMHO, that's the way to do it - fully automated - I'm not as trusting of data that comes from a load being switched on and off while watching a stop-watch and jotting data points on a legal pad.

DaveAK
15 December 2010, 1116
How much does a simple, small load tester cost? And where do you get such a thing?

Richard230
15 December 2010, 1605
Here is the information on the device that is testing my batteries:

http://www.westmountainradio.com/content.php?page=CBA

The attached photo shows the result of the first test. I am informed that the battery put out 29 Ah before the voltage dropped to 2.0.

DaveAK
15 December 2010, 1630
Thanks for the link Richard!

frodus
15 December 2010, 1805
Dave

West Mountain Radio sells a CBA-III (in the picture above). Its a discharger, but its limited to like 100W or something.

I bought a CC-400 discharger, its 400W (can be set up to do 500W continuous) and its a little more robust, but it doesn't measure volts, its just a dynmaic load and I measure volts with a data logger.

Both of these keep the current constant.

DaveAK
15 December 2010, 1818
Dave

West Mountain Radio sells a CBA-III (in the picture above). Its a discharger, but its limited to like 100W or something.

I bought a CC-400 discharger, its 400W (can be set up to do 500W continuous) and its a little more robust, but it doesn't measure volts, its just a dynmaic load and I measure volts with a data logger.

Both of these keep the current constant.
I only have a few cells I'm working with so don't need anything more than 100W, but I don't need the volt measuring side of things either, that's taken care of with my Eval board. A CC-100 would be great, especially if it was under $100. :D I didn't see the CC-400 on the CamLight site for some reason.

harlan
15 December 2010, 1826
That's a very cool test set-up! I had to really look at the details to see the whole robotic setup, I was so focused on the computer at first glance.

IMHO, that's the way to do it - fully automated - I'm not as trusting of data that comes from a load being switched on and off while watching a stop-watch and jotting data points on a legal pad.

Is that robot part of the pro package?

chef
15 December 2010, 1913
That's a very cool test set-up! I had to really look at the details to see the whole robotic setup, I was so focused on the computer at first glance.
LOL same here. If you have a vivid imagination, the laptop's touchpad looks like a nose, and the curved button things below the mouth. The keyboard could be the eyes or a visor. Transformers... more than meets the eye



The attached photo shows the result of the first test. I am informed that the battery put out 29 Ah before the voltage dropped to 2.0.That's pretty bad... 60% of original capacity. Is that one of the worse off cells? Is 2.0v the LVC spec for HiPower cells?

frodus
16 December 2010, 0042
I only have a few cells I'm working with so don't need anything more than 100W, but I don't need the volt measuring side of things either, that's taken care of with my Eval board. A CC-100 would be great, especially if it was under $100. :D I didn't see the CC-400 on the CamLight site for some reason.

get a CBA-II then, find em used for cheap.

the CC-400 info is on RCGroups:
http://www.rcgroups.com/forums/showthread.php?t=938266

and here:
http://www.camlight.com/techinfo/Camlight_CC-400_UserGuide.pdf



do you need constant current? If not, just get some resistors.

Richard230
16 December 2010, 0859
Chef, that is one of the better cells. One that looks worse was being tested last night. My friend that is playing with my GPR-S is an EE who builds, maintains and repairs commercial radio stations. (I don't want anyone to think that I am doing this work myself. Right now I am having problems recharging some AA NiCad batteries.) The batteries are being tested in his shop.

Richard230
16 December 2010, 0919
Here are the latest results from testing four of my batteries. Ignore the green line, it is an error. It appears that just watching how the quickly the batteries charge to a specific voltage may not be a very good indicator of their condition. Test equipment is better than just guessing (like I do). My friend is using a LVC of 2.0 V to protect the batteries. I can't recall for sure what the low voltage cut-off for Hi Power batteries, but I think it is 2 volts.

DaveAK
16 December 2010, 0928
Hadn't thought of a CBA-II, that's a good idea. Right now I am using resistors to simulate the cells. And I've got a 24V 30/60W bulb that gives 2A or 3A load depending how it's hooked up. I'm actually more interested in the charging side than discharge which is why I don't want to spend a ton of money on this. I've already spent far too much.

billmi
16 December 2010, 1002
Is that robot part of the pro package?

I think you and Chef were the only two who actually looked at my version of the picture :-)

Richard230
16 December 2010, 1611
You are right, billmi. I didn't click on your picture. Great job. Is that Robbie working on those batteries? :D

Warren
16 December 2010, 1645
Folks,

Brian never offered to tell us about the Brammo's new batteries. It would appear these are they.

http://www.leydenenergy.com/index.php?page=pouch

http://www.leydenenergy.com/index.php?page=vehicles

Warren

DaveAK
16 December 2010, 1652
I'm glad they've got the fastest bike in the industry. I always wondered who did. :rolleyes: