Cells for high drain battery

Acho123

Acho123

1 mW
Joined
Apr 2, 2019
Messages
10
Hello guys,

After reading some posts here, i couldn't find a definite answer on my question.
I'm planning on building a stealth bomber clone e-bike with QS205 4T V3 motor and Mobipus 72200 controller, and i need help finding adequate cells for the job. My biggest concern is cycle life, i'm willing to give up some performance but have a battery pack that will be reliable even after 750+ cycles.
For now my favourite is the Samsung INR18650-25R, with which i'm planing on building a 20s13p configuration with 150A cont. and 300A peak.
https://eu.nkon.nl/samsung-18650-inr18650-25r.html
They seem to be good, but their cycle life is poor, at least to me: (72% of the original capacity for high drain application, thats 673Wh just gone)
https://endless-sphere.com/forums/viewtopic.php?f=14&t=73883

I even looked at LiFePo4 cells, because of their long cycle life, but i'm not so sure how good they are for e-bike application.
https://bit.ly/2KLCDLb - The best i could find, but as everything from China i can't really trust them.
I've read mixed reviews, someone tested them at 15A cont and they got pretty toasty (75C), also their real capacity is ~5Ah.
A similar battery pack to the Li-ion one will be 8 killos more and much bigger, so i really don't think they are well fitted for this kind of application.

I'm open to any suggestions for good cells :D
 
you can ignore cycles if you stop charging at 4.1V and bottom limit to 3V you will see many more cycles then the datasheet.
check here for tests done with the 29E:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=93989&start=25#p1459171.

the 25E is even more robust so you would see even better numbers then my tests.
 
Hello,

At the moment the best 18650 cell for the same capacity is the: VTC5A
it has the lower internal resistance and the longer cycle life. That's why it's more expensive.

https://eu.nkon.nl/sony-us18650vtc5a-flat-top.html

Many big e bike builders use it for very high power e bike projects like the bellow.
0-100km/h in 4 seconds Crazy fast.

https://www.facebook.com/CyklonEbike/?__tn__=kC-R&eid=ARDSa16BkuyQDYSDx7wOQbaGtnXVFulTNfNc3sgJhPoShJJHnnKU7s3-OKvMtXh2NPyjq-tqlu-a5n4O&hc_ref=ARSnohQqd08wxnQ9fh79geLoo5FlX6omqDk8TzAvDeToxy2i65Oc5O0PLU37iP71SGo&fref=nf
 
Agree with flippy, but would like to add, any cell will do better, if you don't heat them up. When the motor gets big, carrying enough battery without drastically upsetting the handling of it gets hard.

So 1, get the lowest internal resistance cells you can afford, vs choosing a cell for its cycle life when tested at a fraction of the discharge rate you will use.

2 make that pack as many cells in parallel as you can. This might mean running a lower voltage than your dreams, but a good 60v bike will beat a 100v bike that eats its battery. Think performance in terms of fast take off, vs top speed. any bike that does 40 mph is fast enough. Run whatever voltage you can fit in that frame, and keep your cells cool enough to touch with your dick. ( My hands could handle 200f)

3 for faster than 40, start thinking about motorcycles, perhaps you are anyway. Bike frames do have limits. not as much in terms of speed, but in terms of frame performance when overloaded with batteries. So if you want super fast, build your custom frame much more robust than stuff that was designed to pedal. You need a lot more stiffness from side to side. I built this frame only for the purpose of towing trailers, and carrying up to 40 ah of 48v in the frame. But in the end, it was incredibly stiff, and would have made a great high speed frame. Finished cargo mixte..jpg
 
dogman dan said:
Agree with flippy, but would like to add, any cell will do better, if you don't heat them up. When the motor gets big, carrying enough battery without drastically upsetting the handling of it gets hard.

So 1, get the lowest internal resistance cells you can afford, vs choosing a cell for its cycle life when tested at a fraction of the discharge rate you will use.

2 make that pack as many cells in parallel as you can. This might mean running a lower voltage than your dreams, but a good 60v bike will beat a 100v bike that eats its battery. Think performance in terms of fast take off, vs top speed. any bike that does 40 mph is fast enough. Run whatever voltage you can fit in that frame, and keep your cells cool enough to touch with your dick. ( My hands could handle 200f)

3 for faster than 40, start thinking about motorcycles, perhaps you are anyway. Bike frames do have limits. not as much in terms of speed, but in terms of frame performance when overloaded with batteries. So if you want super fast, build your custom frame much more robust than stuff that was designed to pedal. You need a lot more stiffness from side to side. I built this frame only for the purpose of towing trailers, and carrying up to 40 ah of 48v in the frame. But in the end, it was incredibly stiff, and would have made a great high speed frame. Finished cargo mixte..jpg
Click to expand...
hahahaha how is it possible to do this with your d..k ?
I was laughing so much!! Can you explain us how you do this with your battery pack ?
 
Of course I said that for a laugh.

People talk about packs, controllers, motors, getting too hot to handle or touch. After a lifetime in construction, I can damn near handle shit red hot. Others, with tender hands, cannot.

I would call 50f more than body temp not hot, merely very warm. But I bet it would scorch my dick. But if you are that concerned about lifespan, don't build a pack that gets too hot to touch with your dick. Keep it more like very hot bath water, at most. Or if the air is hotter than that, not over the 120F ambient temp in Phoenix AZ.


Hot cells will never deliver the cycle life you want.
 
icherouveim said:
hahahaha how is it possible to do this with your d..k ?
I was laughing so much!! Can you explain us how you do this with your battery pack ?
Click to expand...

its not that hard (pun intended), but it can be a matter of having the right tool for the job.... :roll:
 
Thank you all for the great responses you left, i did some more research and narrowed my options to these:
1. Sony US18650VTC4 2100mAh - 30A
https://eu.nkon.nl/rechargeable/18650-size/sony-us18650vtc4-flat-top.html
A 20s13p pack (611EUR) is 11.7kg and has a 2020Wh energy with 390A cont. discharge, on the downside their IR is 12mOhms

2.Sony US18650VTC5A 2600mAh - 35A
https://eu.nkon.nl/sony-us18650vtc5a-flat-top.html
A 20s10p pack (630EUR) is 9.42kg (better than the C4) and has 1924Wh energy with 350A cont. discharge, IR is much better at 10mOhms.

I'm more inclined towards the Sony C5A as they seem to be the better cell. Ill charge them to 4.1 and discharge to 3.1 to maximize the cycle life.

Still open to other suggestions :D
 
make a 20S13P pack with the C5A.

if you have the space: add more cells!
 
Acho123 said:
I even looked at LiFePo4 cells, because of their long cycle life, but i'm not so sure how good they are for e-bike application.
Click to expand...
Either plan on replacing more often, or go A123 LFP in a pack with more strings to compensate for lower energy density.

Brand new of course, and if not direct from A123 official supplier, from a known-reputable supplier in your country, or at least continent.

In NA this guy, name's Richard http://www.wrongwayrc.com

K2 might also be OK. Dunno any others I'd trust in cylindricals. I prefer prismatic myself, but not stealth :cool:

And anything at high C rates do not expect many decades of lifespan, even sacrificing range avoiding the voltage shoulders.
 
flippy said:
make a 20S13P pack with the C5A.

if you have the space: add more cells!
Click to expand...

Yes do this and you won't regret it!!
You will have great performance and good cycle life because with 13P every C5A cell will have to deliver only 15.5A so they won't get very warm.
 
Also there are more option for you, for example there is a new high power 20700 cell from Sanyo but is more expensive.

NCR2070C
https://www.nkon.nl/sanyo-ncr2070c-3500mah-30a.html

It has more capacity and the internal resistance is only 10mΩ. You can read bellow.

http://www.evva-tech.com/plus/view.php?aid=213

https://m.facebook.com/batterymooch/posts/2089343858021856
 
If you're going to use car-type discharge rates, you should consider using car cells. Even if you can find small cylindrical cells that are workable with your discharge rates, the numerous interconnects are likely to get warm and/or drop your voltage. And they represent that many more opportunities to have a fault.

I have better things to do with my time than assemble, maintain, inspect and troubleshoot 260 cells when I could use 20 (or 40) instead.
 
No such thing as "car cells". Many EV use hundreds of the tiny cylindricals.

The big rectangular cells are called Prismatics.

CALB 180Ah are a great example, but for small EVs likely need to use smaller units like 60Ah.

Can be hard to fit, and certainly not stealth.
 
It's nice to see so much activity on my question.

For now i've scraped the idea about the LiFePo4 cells. My vision is for a battery pack either 20s13p or 20s15p with the C5A cells.
My controller will be 200A continuous so i think they will be nice and cool.
About the connections i plan on using 99% nickel strips 0.3mmx12mm, also the series connections will be reinforced by soldered copper wire for least resistance. :bolt:
 
Acho123 said:
It's nice to see so much activity on my question.

For now i've scraped the idea about the LiFePo4 cells. My vision is for a battery pack either 20s13p or 20s15p with the C5A cells.
My controller will be 200A continuous so i think they will be nice and cool.
About the connections i plan on using 99% nickel strips 0.3mmx12mm, also the series connections will be reinforced by soldered copper wire for least resistance. :bolt:
Click to expand...
I think you have made a good decision.
Don't forget to show us some pictures when the battery pack is ready! In the meantime you can watch the polish video I sent you to take a taste from the ultimate ebike power!
 
Acho123 said:
I'm planning on building a stealth bomber clone e-bike with QS205 4T V3 motor and Mobipus 72200 controller, and i need help finding i'm planing on building a 20s13p configuration with 150A cont. and 300A peak.
Click to expand...

I have two remarks for this assumption:

1) 150 A cont. at 72 V nominal gives you 10kW shaft output power with 92 % efficiency. Are you aware that 10 kW is average consumption for electric vehicle with ca 1500 kg curb weight cruising at ca 50 km/h?

2) QS205 50H V3 motor is rated as 3 kW continuous. Is more than likely that your average consumption will be lower that 1500 W.

But the decision of choosing 20s13p (2.6 kWh with 29E or similar cells) is correct for this application and this will gives you excellent cycle life even if you will frequently use 90% DoD (in fact you will be still above 70% of intitial capacity after 1000 cycles at 100% DoD with 29E).
 
those numbers should make it pretty "sprighty" off the line.

a 205 can take short bursts of 8kW fine, some even go way beyond that but then you run a real risk of burning out the phases.

still, 150A continous on the battery would mean it would do 150kph so i dont think that is not the case.
 
john61ct said:
No such thing as "car cells". Many EV use hundreds of the tiny cylindricals.
Click to expand...

Teslas do it, for reasons that are unique to Tesla. All other e-cars and hybrid cars I'm aware of use large format cells (prismatic and pouch), for engineering reasons.

If you're using hundreds of cells on a bike, you're simply doing it wrong.
 
https://youtu.be/pWdd6_ZxX8c

I happen to agree, in that I prefer lower cell count, going with large prismatics whenever possible.

But that is a personal decision, I can definitely see reasons for using cylindricals, and try to avoid disparaging others for their choices any more than what's required to convey objective fact.
 
john61ct said:
But that is a personal decision, I can definitely see reasons for using cylindricals, and try to avoid disparaging others for their choices any more than what's required to convey objective fact.
Click to expand...

Hey! I found some cylindrical lithium ion cells on Alibaba for less than $.04 each!
https://m.alibaba.com/product/60759912679/SNeng-3-7V-Rechargeable-Li-ion.html

6500 of those should make a nice 48V 20Ah bike pack that can be shaped to fit almost any frame. Cheap, too-- less than $250 per kWh and each in its own metal case. What a bargain!
 
I've already agreed with you. Seems like a lot of effort for a "joke", I guess sarcasm bring you pleasure? Also button cells are a separate category :cool:

Posting purchase links to LFP prismatic cells in a suitable form factor Ah capacity for building that 48V 20Ah bank would actually be constructive.

I would have no problem with paying well over $250 per kWh delivered,

for known-good makers like Winston/Thundersky, CALB, GBS & Sinopoly.

A123 over K2, but not sure if they make bare cell prismatics.

Do other LI chemistries even come in prismatic form in a case, ready to go?

 
prismatic is troublesome to use as you need massive steel supports to compress them. that often negates any advantage they might have.
i'll switch to prismatic/pouches once they start making professional power tools with them.
 
Yes compression plates

1/4" aluminum, two sides only, plus four rods, neither expensive nor difficult really.

Can become the basis for the protective enclosure, which often needs fabbing custom anyway.

But in low C-rate use cases other than propulsion, proper "longevity care" usually prevents any such bulging, or at least insignificant so compression isn't needed.
 
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