Can hk lipo be beaten for this application?

You want a crazy city bike wheelie machine (top speed 45kph or so). Cromotor is too expensive so you go for an mxus 3000, assuming it can take 6kw in 2-3 second bursts from standstill. You want a pack that is assembled or easy to assemble, no soldering. You need 1kwh of battery. How would you power it?

Alternatives I found:
Low power lifepo4 - pack becomes enormous, very expensive and a lot of energy you dont need. Example: INR18650-29E cells from em3ev.com, 50v 24,8Ah triangle pack, 2C, (~2,5kw) cost $964. Need 4 of them - so cost is ~$4000 (!).
(http://em3ev.com/store/index.php?route=product/product&path=35&product_id=123)
Medium power lifepo4 - pack becomes expensive. Example: INR18650-20R cells from em3ev.com, 50v 18,5Ah triangle pack, 10C, (~10kw power) cost $789.
(http://em3ev.com/store/index.php?route=product/product&path=35&product_id=123)
High power lifepo4 - 6s2p, 12 of them = 1kwh, 30kw continous, price $700.
(http://www.hobbyking.com/hobbyking/store/__10311__Turnigy_4500mAh_6S2P_30C_LiFePo4_Pack.html)
hk lipo hardcase 4s 5ah - 14 of them = 20kw continous (30kw burst), $378. Pack is about 5 liters, 7kg.
(http://www.hobbyking.com/hobbyking/...1P_14_8v_20C_Hardcase_Pack_US_Warehouse_.html)

What alternative would you use to satisfy the conditions? Did I miss any good alternatives?

(Side note: The hk lipo packs are very hard to ignore. The main problem they have are of course the fire hazard. Could probably be handled with a steel/ceramic charging station/pot, and put all the packs inside one of those lipo flamesafe bags inside the battery pack casing. )

The first three are not LifePO but Lithium Ion with NCA Kathode from Samsung.
But the 29E is way to weak. You need at least 6C if you only want a 1kWh pack.
My suggestion would be using 18650 cells, because any kind of LiPo pouch is very sensitive and the HK is just bad quality and overrated and also are very heavy.
The Samsung 25R is a ideal canditate as its very powerful (4kw/kg) and very lightweigth (200wh/kg) also it will last twice than the hk lipos.

Very common, unless you have a deep wallet, to power a 50 mph ebike/flyweight motorcycle with hobby king packs. (45 kph is not usually a wheelie machine)

But for the hot rod bike, you don't want the 20c crap. Those are fine for commuters, or running 40 amps or so. But for a haul ass bike, you need 30-40c stuff unless you are going to carry 20 ah or more of it.

100v 10 ah of good packs can still weigh in under 15 pounds, and run a 10,000w bike, fits in a small pelican case or a pair of small boxes carried like saddlebags on the top tube.

As for safety, it's not rocket science. Just common sense.

Sort the packs when you get them, get rid of any shit packs.

Charge them and store them where you would build a fire. That means not in your apartment, not in your garage, etc.

Don't tape them to the bike and crash, dinging them. Don't drop em. Carry them protected so you don't crush the corners and ruin them.

Monitor discharge, and stop before you get in danger of over discharging them. 3.6v is a good line to try not to go below. You can take them deeper of course, but it's hard to watch a voltage display while riding 50 mph on dirt.

I'm assuming dirt riding, since a flyweight motorcycle is illegal to ride on the street in most of North America.

For a wheelie machine, I would have assumed you want, a ton of torque off the line, and not top-end speed.
Which I keep assuming is Amps for torque, and volts for speed. But sometimes I get the impression that I am mistaken.

But for the hot rod bike, you don't want the 20c crap. Those are fine for commuters, or running 40 amps or so. But for a haul ass bike, you need 30-40c stuff unless you are going to carry 20 ah or more of it.

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So you are saying 30-40C in 10Ah, and perhaps 20C in the 20Ah range? For a "Wheelie Machine"
So if you are rocking 84V 10Ah in 35C I assume thats max, so 350Amax. And for 20Ah, 84V 20Cmax is 400Amax.

Thats one thing that I am dissapointed in, with my mxus 3000w. That low-end grunt that I am seeking, not so much that top speed.
I have many factors playing against my ideal ride. One of which is the 40A default on a 18fet, and perhaps choice of battery.

My suggestion would be using 18650 cells

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That is a "Form Factor" many flavors, but always Li-Ion? Or could be any category of chemicals?

Rc lipo is the only choice for a low cost battery with plenty of power. I did a lot of research when I got into ebikes over 4 years ago and determined it was the only sensible choice then. Almost everyone tried to steer me towards lifepo4 at the time, but during my research I found them too weak. 10 year 2000 cycle life was based on 0.2C discharge, and most packs were dying in under 3 years, and some under 1 year. So I went with rc lipo and have never regretted it. Now on my fourth year and over 12K miles with my current 10ah 24s pack. If your controller is 40A max or more, forget anything else for a small ah pack. If using 18650's or most lifepo4, then build a battery pack with ah to match your controller max amp draw if you want it to last over a year.They are best used at 1C max.

Wiht 18650 i mean, powerful cells like the Samsung 25R or the Sony VTCs with really low IR. They are way lighter than lipo,have bettery cycle life, are safe and just a tad more expensive.
But if you really want high power, you only have the LiPo choice with 130C peak cells. But that amount of power is so crazy and no one likes to ride his ebike only 10 Minutes.

If it's not such a hotrod bike that you require stupendously high RC lipo c-rate, I would use the new 3.4Ah LG cell in a pack with no soldered cell connections.

liveforphysics said:

If it's not such a hotrod bike that you require stupendously high RC lipo c-rate, I would use the new 3.4Ah LG cell in a pack with no soldered cell connections.

Click to expand...

Thanks for all responses!


Luke, how would one construct such a pack? I have seen the regular e-bike alu cases been cut open, where the cells lie in perfect rows - sweet! But never found a diy kit?


After feedback from this thread I am definately sttering clear of the mxus 3000. Is there only the cromotor or crown left in the game, are there no new sweet kits? Maybe a hubmonster "bicycle"? Or a deathbike mini (diy mid drive), but such a project seem very hefty, unless I get ahold of the unicorn, mongoose cx 450.

I believe the mxus is the best bang for the buck, at ~$320.
The cromotor or crown are crazy pricey.

For a 3000w wheelie machine, a slower wind muxus would be nice. Then you could keep speed down to about 30 mph, and feed it 6000w. People mistake stalling longer for more power. You do feel the difference when your motor stalls for 1/2 second less time on a start.

Lots of good shit coming down the pipe for better batteries, but just not as cheap and accessible as Hobby king shit packs.

Of course, if you really want to wheelie, build a 6000w mid drive. Where did that shoe go? You know this bike is dangerous.

Hey guy!

After feedback from this thread I am definately sttering clear of the mxus 3000. Is there only the cromotor or crown left in the game, are there no new sweet kits? Maybe a hubmonster "bicycle"? Or a deathbike mini (diy mid drive), but such a project seem very hefty, unless I get ahold of the unicorn, mongoose cx 450.

Click to expand...

So it appears you're aware of middirect drive? (evolutiongts bht mongoose).
I have mimicked his build on my own- an xc bike. ALOT of fun!
Also, are you aware of skeetab's genesis bht build?
Maybe it's close to what you're looking for, and not super hard to pull off.
Imo, the hardest thing is getting the motor freewheeling and keeping all the bike gears in a 155 d/o. But that's not even absolutely necessary for the desired ride you're describing.

Also, on the batteries, I like lipo for the power to weight ratio. Add a bms for even more control, but they are less reliable and more dangerous than the round cells or a123 packs. A trade off, so it depends on your exact definition of 'beaten' I guess.
Beaten for power to weight - no.
Beaten for safety and reliability - yes.

dogman dan said:

For a 3000w wheelie machine, a slower wind muxus would be nice. Then you could keep speed down to about 30 mph, and feed it 6000w. People mistake stalling longer for more power. You do feel the difference when your motor stalls for 1/2 second less time on a start.

Lots of good shit coming down the pipe for better batteries, but just not as cheap and accessible as Hobby king shit packs.

Of course, if you really want to wheelie, build a 6000w mid drive. Where did that shoe go? You know this bike is dangerous.

Click to expand...

:lol: I can relate to lost shoes, just not on a ebike, more weekend benders. Unexplained bruises. :lol:


Slower wind = less Kv = More T count = wheelie machine
So my 4T = Fast wind, hence more Kv (rpm/volt)
I Shoulda bought the highest Tooth count (6T, 7T, 8T) more torque off the line, 1/3 more torque off the line.

Very hard to beat RC Lipo for this application.
You do not only need power, but significant amounts of capacity because you are blowing through power very quickly.
For this kind of setup, i'd go with the 190whrs/kg multistars over 18650s any day. Though the Samsung 25R is looking pretty good these days, i'm not sure if it could output adequate power without sagging a lot.

neptronix said:

Very hard to beat RC Lipo for this application.
You do not only need power, but significant amounts of capacity because you are blowing through power very quickly.
For this kind of setup, i'd go with the 190whrs/kg multistars over 18650s any day. Though the Samsung 25R is looking pretty good these days, i'm not sure if it could output adequate power without sagging a lot.

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Here you go again with your multistars... Haven't you see my post about them in another topic? You didn't reply because there was nothing to add... mulstistars suck, they are actually ~3C batteries, and that makes their 190Wh/kg suck, since 25R are real 8C and 210 Wh/kg. Any also multistrars are more expensive then samsung 29E cells which have similar C rate, bit lower, but they are around 240 Wh/kg and brand name, made in korea cells, and they are few times more reliable and will last much longer, not to mention safety. Panasonic PF are bit more expensive, even greater quality and 3C rate.

neptronix said:

Very hard to beat RC Lipo for this application.
You do not only need power, but significant amounts of capacity because you are blowing through power very quickly.
For this kind of setup, i'd go with the 190whrs/kg multistars over 18650s any day. Though the Samsung 25R is looking pretty good these days, i'm not sure if it could output adequate power without sagging a lot.

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I like the picture! =) Which cells belong in the red rightmost box?
Also, "not modular" - why cant you just make small packs of 18650, say 8 cells, you can configure them 8s1p or 4s2p, or a 6 cell, 10, 12 cell - are there any such production packages? What could such a pack cost from china, high qiality, $5? Invent it already! =P

I don't agree with you here. An ideal use case for any battery is to use it at 1/4th the maximum C rate continuously. 3C is proper for long term usage with multistars then. 2-2.5C is that max i'd run the Samsung 25R at.

Not due to heat, but due to voltage sag. The more you sag, the less watt hours you get out of the battery. Watt hours is actually a moving target.

I didn't reply because i didn't see your post.

There is still no 18650 i am interested in buying a battery welder and doing all that manual labor for. The 25E comes very close. For the 100A output i need, i'd need a 50AH 25E pack to get that output comfortably. I'd rather have 40AH of mutistar, as it'd be way easier to assemble and make use of.

riba2233 said:

neptronix said:

Very hard to beat RC Lipo for this application.
You do not only need power, but significant amounts of capacity because you are blowing through power very quickly.
For this kind of setup, i'd go with the 190whrs/kg multistars over 18650s any day. Though the Samsung 25R is looking pretty good these days, i'm not sure if it could output adequate power without sagging a lot.

Click to expand...

Here you go again with your multistars... Haven't you see my post about them in another topic? You didn't reply because there was nothing to add... mulstistars suck, they are actually ~3C batteries, and that makes their 190Wh/kg suck, since 25R are real 8C and 210 Wh/kg. Any also multistrars are more expensive then samsung 29E cells which have similar C rate, bit lower, but they are around 240 Wh/kg and brand name, made in korea cells, and they are few times more reliable and will last much longer, not to mention safety. Panasonic PF are bit more expensive, even greater quality and 3C rate.

Click to expand...

helpfulguy said:

I like the picture! =) Which cells belong in the red rightmost box?
Also, "not modular" - why cant you just make small packs of 18650, say 8 cells, you can configure them 8s1p or 4s2p, or a 6 cell, 10, 12 cell - are there any such production packages? What could such a pack cost from china, high qiality, $5? Invent it already! =P

Click to expand...

I made this image before newer cells like the 25E and 30Q were widely available. When i made the image, the only high output 18650s were around 2200mah, so i based it off that.. the newer cells are going to be better.. i haven't seen anyone fill a triangle with them yet though, so what's in the red is an assumption.

Yes, you could assemble modular packs like that, for sure. There's just an investment in equipment and learning curve involved.

Have you looked here? Close to home. http://endless-sphere.com/forums/viewtopic.php?f=31&t=61608&p=1070916#p1070916
I'm sure you can find something there.

Dan

High Energy
or
High Power

Whats the different?

High Energy
or
High Power

Whats the different?

Your serious about 25r being 2 to 2.5C?

markz said:

High Energy
or
High Power

Whats the different?

Click to expand...

HE = bigger capacity

HP = more current

Wish I had a link to the time Luke loaned his death bike and the guy wheelie so hard he might have a second ass hole. You can hurt yourself with a titchy throttle. You just can't understand. Because you will be on your ass scratching your head and wishing you spent money differently.

Do you mean the "And you know this bike is dangerous?" video, with the shoe flying a few seconds later?
[youtube]NCpzXIPXdAQ[/youtube]

neptronix said:

I don't agree with you here. An ideal use case for any battery is to use it at 1/4th the maximum C rate continuously. 3C is proper for long term usage with multistars then. 2-2.5C is that max i'd run the Samsung 25R at.

Not due to heat, but due to voltage sag. The more you sag, the less watt hours you get out of the battery. Watt hours is actually a moving target.

I didn't reply because i didn't see your post.

Click to expand...

Well, hk lipo has fabricated maximum c rate, and 18650 brand name has realistic declared maximum c rate. 18650 comes with datasheet which shows realistic operating conditions, including chart with discharge curves and cycle life at max c rate. Hk cells are toys, they are no name and don't even have datasheet or any safety certificates. Hk cells also sag like shit at their "declared" C rate (how is multistar at 10C continuous? we know how 25r does at 8C) and they will do something like 50 cycles at their declared discharge, while 25R and other will do at least 250 cycles at maximum c rate charge and discharge (4 A charge, 20 A discharge, and even at 30 A, which is over their max). So, you must consider that points and be fair when comparing these cells and their declared c rate.

markz said:

Your serious about 25r being 2 to 2.5C?

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Just look at what the 25r does under discharge and you can figure that out. You can do this with any cell discharge graph.



At 2C ( 5A ), the cell just drops to about 3.7v nominal and you aren't losing much power at all there. Notice that the cell barely generates any heat - just a 10C rise. This is good. You won't need to worry about building your pack with some sort of cooling mechanism to control this level of heat.

At 4C ( 10A ), the cell drops from being ~3.75v nominal to 3.5v nominal.
You've lost a notable amount of your whrs/kg to heat doing that. And the cell heat has risen about 30C. If you have a pack with cells smashed against each other, they're getting hot... especially the cells in the center. You absolutely need some kind of cooling here.

At 8C, this cell's now um.. 3.3v nominal? and your cells are hot enough to burn each other or something else. You've lost 12% of your battery's energy to heat. If you have a 1000whr pack of these, you've delivered 880whrs to your controller and produced 120whrs of the energy worth as heat. Not something you want to do without extensive liquid cooling, which will also require extra mass or a circulating pump ( even more energy loss there ) to manage without killing the battery quickly.

..and this sucks for the performance of your bike too. If you're discharging the cell at 1C, you're seeing about 48.75V nominal.
If you discharge it at 8C, you see about 42.9v nominal, which is close to where your LVC should be set for a 48v nominal pack :lol:

So, the best use case for a battery build with no cooling built in is around 2-2.5C for that cell.

I do not have a similar sheet for the turnigy multistars, but Christoffer Parham is as picky about i am about cell efficiency, and he said 2.5C is the ticket for the multistars. I saw his data last year.

I would not run a multistar or the nicest 18650 in the world at their max rating.
The '1/4th the rating' rule applies to pretty much all batteries.
The max discharge rating of pretty much every battery is the point right before they blow up :lol: not where you see the most performance, efficiency, and cycle life.

Motors are rated at their nominal continuous wattage where you see best efficiency. Batteries can be thought of the same way by dividing their max discharge by a fourth.