Scavenging one nearly new battery to make another?

Batteries, Chargers, and Battery Management Systems.
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Re: Scavenging one nearly new battery to make another?

Post by 999zip999 » Mar 20 2019 12:54pm

Get the book.

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 20 2019 5:14pm

K2 cells

good company

y'all think their LFP cells good as A123?

https://batteryhookup.com/products/20-k ... teries-new

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Re: Scavenging one nearly new battery to make another?

Post by Hillhater » Mar 20 2019 5:54pm

john61ct wrote:
Mar 20 2019 5:14pm
K2 cells
good company
y'all think their LFP cells good as A123?
https://batteryhookup.com/products/20-k ... teries-new
No !
Those K2 cells have the advantage of being cheaper and higher capacity than A123
But ....their output ability is a fraction of A123 (70 amp continuous !)

The OP needs to recognise the major dissadvantages of using LiFePo in this application
His only realistic chance of building a 72v , high power, low cost, pack with reasonable range and a possibility of fitting in the frame space....is (as DD said ), to use RC lipo pouch packs.
But that is the compromise i warned obout of reduced cycle life compared to LiFePo.
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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 20 2019 10:07pm

Surely besides the 2D triangle dimensions, thickness can be extended?

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dogman dan   100 GW

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Re: Scavenging one nearly new battery to make another?

Post by dogman dan » Mar 21 2019 7:01am

4 inches wide battery box in the triangle is very comfortable, which is why a single stack 18650 pack fits great in a triangle bag. How to stack more 18650's in the triangle without going to a double stack, 8 inches wide is a problem. You can pedal around 6" wide, but its awkward. 5" wide is not bad, but you do start to have to sit the saddle different even at 5" wide. A double stack of 18650's means you are pretty much done using the pedals at all. You pedal so bowlegged that you will soon tire of it.

But,,, not like that's a problem when you run 72v, and run too fast to pedal 90% of the time. :twisted:


As for the van truck,, I always wanted the van truck, the single cab one. badass conversion.


I DO UNDERSTAND how much carrying 20 pounds on that rack sucks. I have done lots of off road riding e bikes. All my bikes though, had the Y frame suspension, so no triangle at all to carry batteries. I had to come up with ways to eliminate that rack battery too.. I'm not spewing thoughts at ya, but experience. My highest power bikes ran 72v, at 3000w. I carried 4 lipo packs on each side of the Y frame of the bike, and put the controller on the rear rack, and a tire pump. 10 ah of 72v lipo, about ten pounds of pack, able to put out 40 amps with ease. 10 ah of 18650's putting out 40 amps will get all hot and bothered every ride, and likely die fast. You want that battery in the triangle, but not much will fit. So you have to carry more somewhere, or you have to lower the controllers power.


After lowering my power to 48v, and deciding that I really did not need 40 amps all the time, I found that by adjusting my body weight just a tad forward as I rode, 8 pounds max on a rear rack was not so bad. I currently carry about 6 pounds there. The flip side is now I can actually pedal the bike. Before, not really. I don't have the wheelie problem at 1000w, that I had at 3000w. But I can't climb as steep a hill either. Always its a compromise. Three things I want, two I get.


So I made adjustments, to the power I used, the way I stood the bike, and how steep a hill I climbed. Speaking of hills,, regardless of that rack, you will wheelie off the bike at about 20 degrees. I think % grade up to about 15%, then my ski mountaineering kicks in and I think in degrees. Sand, on the slip side of the face will be about 30 degrees. So anyway, you will never have a bike with enough power to wheelie, that won't wheelie worse up grades over 15%. Riding up 20 degrees is close to impossible, once you start to lose momentum. You just wheelie off at about that grade. On anything, including a badass trials motorcycle. So one adjustment you need to make is that even without the rack and battery, you are going to continue to wheelie off that thing on the steepest sand hills.

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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 21 2019 6:49pm

You guys expose my ignorance at every opportunity! And take a certain amount of perverse pleasure in it as well. :lol:
That's okay, I'm used to it. I don't give a dam about 72 volts per se, but short of that then what way can I take full advantage of the 3k watts the Cyclone can put out? And like I said earlier... it's going in the triangle or it ain't going.

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Re: Scavenging one nearly new battery to make another?

Post by Hillhater » Mar 21 2019 11:20pm

Forget LifePo..
Get 2 of these.. For <$400. (Or 3 if you really want 72v)
https://hobbyking.com/en_us/turnigy-hig ... -xt90.html
Series connect ..easy.
< 5kg, 48v , same capacity as your current pack , but 3kW no problem.
Learn how to manage packs without a bms.
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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 22 2019 7:29pm

Another option, known-good reasonably priced source for Sony / Murata VTC6 under $5 or 43¢ per kWh

https://endless-sphere.com/forums/viewt ... 9#p1453699

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 22 2019 7:50pm


Hillhater wrote:Get 2 of these.. For <$400. (Or 3 if you really want 72v)
https://hobbyking.com/en_us/turnigy-hig ... -xt90.html
Series connect ..easy.
< 5kg, 48v , same capacity as your current pack , but 3kW no problem
Please correct me if I'm wrong. Nominal 3.7Vpc, 6S = 22.2V

12S only gets to 44.4, I figure need 14S for 48V ?

And nominal 72V would usually mean charging @88+V, so 21S ?


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Chalo   100 GW

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Re: Scavenging one nearly new battery to make another?

Post by Chalo » Mar 22 2019 11:01pm

john61ct wrote:
Mar 22 2019 7:50pm
Hillhater wrote:Get 2 of these.. For <$400. (Or 3 if you really want 72v)
https://hobbyking.com/en_us/turnigy-hig ... -xt90.html
Series connect ..easy.
< 5kg, 48v , same capacity as your current pack , but 3kW no problem
Please correct me if I'm wrong. Nominal 3.7Vpc, 6S = 22.2V

12S only gets to 44.4, I figure need 14S for 48V ?

And nominal 72V would usually mean charging @88+V, so 21S ?
13S is nominal 48V; 14S is nominal 52V, and 20S is nominal 72V.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: Scavenging one nearly new battery to make another?

Post by Hillhater » Mar 23 2019 1:25am

john61ct wrote:
Mar 22 2019 7:50pm
Please correct me if I'm wrong. Nominal 3.7Vpc, 6S = 22.2V

12S only gets to 44.4, I figure need 14S for 48V ?

And nominal 72V would usually mean charging @88+V, so 21S ?
you are correct !
But, it does not matter in reality, and it complicates assembling a pack from RC lipo, which is commonly available in 4s, and 6s, "bricks".
And RC lipo has a different discharge character to 18650 cells...
12s RC lipo gives 48+ volts fully charged, and at 2-3 C discharge, you have little sag... Full discharge is around 3.6 v.
So 12s RC lipo minimum voltage is 43 ish volts.
13 s VTC6 sags much more ( higher DCIR)... Its down at 3.5v almost from the start with a 10a load. and full discharged voltage is 3.0 v....(if you want to use the capacity)
So 13s VTC 6 .minimum pack voltage 39.0 v
Get the point ? Average pack voltage using 12s RC lipo is HIGHER than using 13 s VTC 6 of the same ah pack size)
Likewise for a "72" volt, 18s lipo vs 20s VTC pack. ( 21s fully charged, would kill some controllers!)
But of course you could run 14s or 20s RC packs. ... (4s+4s+6s.. And 4s+4s+6s+6s ), but that just adds cost, weight, complexity, and size to the pack !
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dogman dan   100 GW

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Re: Scavenging one nearly new battery to make another?

Post by dogman dan » Mar 23 2019 7:29am

Only lipo will put out 3000w at 48v. 10 ah at most will fit. So you need something able to put out 20c in reality. which means the way they lie about the c rate at hobby king. you need about 60c type or better.

You can get 2000w of 48v easier, meaning your controller is set to 40 amps. Then you can use the cheaper lipo there is out there. Something like these would work real good for 2000w of 48v, buy 4 for a 48v 10 ah pack. https://hobbyking.com/en_us/turnigy-hea ... -xt90.html

It would be about 140 x 110 square, and 150 or so long. Should cram in the triangle no problem at all. I've carried the same thing in a triangle bag, without using any of the space in the bottom tip of it. I run a similar pack on my 2000w beach cruiser right now, with very good performance. Battery barely warms up, bike goes 30 mph. That bike has a huge watt hungry hub motor, and 40 amps controller. But the 60c lipo takes it like a champ. 40 amps is a 4c discharge, but the battery is realistically capable of 15c. So its performing great. It would be able to do 3000w with equal ease.

What the hell is c rate. its a way to express the rate of discharge. 10 ah at 1c is 10 amps. 10 ah will fit in your triangle, so to get 60 amps at 48v, it will discharge at 6c. What you want is a battery rated for 2 to 4 times that 6c.

What you can fit in 18650's in your triangle, with the motor taking up a third of it already, I already linked you to. I did not mean you buy that pre made pack per se. But you do need that kind of quality cell, and that's about the most you will be able to cram in there. And then,, limit your discharge rate to closer to 20 amps, or 25 amps.

You keep asking for more than you can have in 18650's. Those are about 4c, but really,, 2c to perform good. ( this is where I keep getting 20 amps limit on your controller) Fine, but you just won't get it. ( 6c from 18650's, and it lasts) If you want to go buy a battery that won't last go ahead. I'm sure 90% of us here have done that. :lol: I have made that mistake quite a bit more than once.

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Re: Scavenging one nearly new battery to make another?

Post by 999zip999 » Mar 23 2019 8:10am

My A123 20ah pouch can put out 100amp. In real life and live long life . Can you fit the size ? Hold the weight.

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 23 2019 10:01am

999zip999 wrote:My A123 20ah pouch can put out 100amp. In real life and live long life . Can you fit the size ? Hold the weight.
But if that is LFP, isn't it a very low energy density, takes more space and weight to carry the same Wh?

Range is important here not just acceleration, right?

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mammonista   10 W

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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 23 2019 11:17am

I bought the book. When it arrives I'm gonna have to read it (several times cuz I'm kinda dense) and then re-read all of these frickin' posts. I'm getting really confused with lithium battery terminology and different cell chemistry terminology and the fact that you guys use shorthand to refer to the different kinds of batteries.
And the fact that maybe, maybe a lot of you have different favorites when it comes to the various battery chemistries. "I like small block Chevy's". "Chevy's suck, I'd go for a Boss 302 any time!" etc.
My Cyclone 3k mid-drive motor (do any of you even use one of these motors?) is rated to take a full 72-volts to produce 3,000 watts. Some of you say that it's impossible for a custom-built 18650 pack, even one built from fairy dust and Unobtanium, that will do that and still fit inside the triangle. Others say " 'bunk!' If the Unobtanium was harvested by pixies and sprinkled on the 18650s in total darkness during a full moon it will work just fine".
I give up! When the book arrives I'll read it several times and then continue my quest for the Grail filled with lithium (and maybe a small amount of Unobtanium).

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 23 2019 3:29pm

Yes there is no universal Best for all use cases.

I personally like LFP because my uses favour safety and longevity over energy density and maximum discharge rates.

But now I'm learning that LFP (which I guess means A123 in this context) is way up there even in actual max discharge rates.

So to me, that leaves energy density as the only Con against LFP.

But that seems to be the #1 super-critical factor for bikes, which is why LFP is rarely used here.

Plus up-front cost outlay, I prefer to look at per-year per-cycle instead and sub-C usage is conducive to decades' lifetimes, propulsion not as much.

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Re: Scavenging one nearly new battery to make another?

Post by Hillhater » Mar 23 2019 5:58pm

dogman dan wrote:
Mar 23 2019 7:29am
Only lipo will put out 3000w at 48v. 10 ah at most will fit. So you need something able to put out 20c in reality. which means the way they lie about the c rate at hobby king. you need about 60c type or better.
:shock: :o :?: :?:
20C (200a) at 48v would be 9.6 kW
I think you have made a typo somewhere ?
Im pretty sure you could get 2 of those 20 ah Mulistar, 10C, 6s bricks inside the triangle and squeeze 3C (60amps) out of them.
OP......
There is no one book that will explain the specifics of your situation and battery options.
You are reading the best source of relavent info right here on this site.
Read some of the "sticky" posts at the rop of this forum.
As i said before, its all a compromise between, performance (volts , amps ), energy density (weight), size, cost, complexity, availability , etc etc.
You could make a 18650 pack to supply 3 kW, and fit in the frame, but it would have rediculously small capacity and range. Hence the suggestion of Lipo pouch RC packs.
I repeat also, Lifepo will simply double the weight and size for an equivalent Ah capacity.
Safety..
M. Most battery incidents (fires) are caused by damage, poor pack assembly, wiring shorts, overcharging/excess discharging, BMS failure, human error etc. ....rather than any specific cell chemistry.
Remember those priorities, ? Some are mutually exclusive, you cannot have a small high power, high capacity, pack for low cost, something has to sufferq
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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 23 2019 6:04pm

LFP is inherently **much** less prone to thermal runaway than the other LI chemistries.

Not saying that is important to most, nor in this case compared to the other variables.

But the difference is huge, IMO safer than lead banks.

That said yes, driving at speed on our highways with a tank full of petrol is a much bigger risk we take without thinking.

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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 26 2019 9:56am

GET THE BOOK! yeah! great advice!
Thank you 999zip999 for the tip. Helped clear up a lot of the terminology CONFUSION for what you guys mean when you don't know exactly what you mean but are just following everybody else's not know exactly what they mean! I now know exactly what you mean (or think you mean) when you loosely refer to Lipo batteries! I could have gone months trying to decipher everything said here. And I'm not trying to be snarky, it's just that when newbies are talking with people who have been doing this for years the newbies (like me) get confused when the terminology has evolved to mean something entirely different than what it started out meaning. I now realize that 'lipo' has become slang for 'rc lipo'. I now have a pretty good idea of the different Lithium Ion chemistries available for the venerable 18650 battery architecture and the corresponding battery name from at least some of the big manufacturers. I now have an idea of what to consider outside of 18650s, although that seems to be venturing into dangerous territory for a newbie. Pouches are out, as are probably anything not 18650. But now I have a reference to go back through all of these comments and say "right", or "wtf was he thinking", or "no effing way!" So once again...
GET THE BOOK! YEAH!

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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 26 2019 11:09am

So the author (Micah Toll) says I should go with NMC (Lithium Nickel Manganese Cobalt Oxide) or NCR (Lithium Nickel Cobalt Aluminum Oxide) 18650's, made by Samsung (INR18650-25R) and Panasonic (NCR18650B) respectively. I can get the Samsung cells (2400 mAh) for $3.00 each on Ebay from a trusted seller and the Panasonics (3200 mAh) for $4.65 each.
1) Which is the favorite here?
2) Are there newer versions of these specific chemistries I should be looking at?
3) How many of each would I need to make a reliable 72-volt, 12ah battery in a custom enclosure?
The above prices are for lots of 100 batteries which seems doable.
Thanks in advance!
p.s. I'm still reading the book for the answer to question #3, but since it was written a couple of years ago I'm sure answer #2 may have changed, and answer #1 is subjective but very important for my build!

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mammonista   10 W

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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 26 2019 11:54am

starting to make sense to me... (a difficult thing at best!)
if I build a 20s4p battery using the Samsung cells, rated at 2400 mAh, I would get a 74 volt (nominal) battery with a 9.6 AH rating.
if I build a 20s4p battery using the Panasonic cells, rated at 3200 mAh, I would get a 74 volt (nominal) battery with a 12.8 AH rating.
***At the ebay prices the 9.6 AH 'Samsung' battery would cost me $240 bucks. If I went to 20s5p configuration there I'd spend another $60 but have a 12AH battery. So for $300 I'd have my 12AH but have to deal with 100 cells!
***At ebay prices the 12.8AH 'Panasonic' battery would cost me $372 bucks but only be 80 cells big.
Do I have that right?

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 26 2019 4:29pm

Didn't do the math, but bringing dollars back to "per kWh" helps compare apples to apples.

Why not try doing that with your prospective cells so far?

Of course that's just storage capacity, nothing to do with the (mythical) max continuous discharge ratings.

Note a 4.2V chemistry cell will convert mAh to watts differently from a 4.7V or a 3.6 one like LFP.

And that these are charging setpoints, not "resting actual" nor "nominal" voltages.

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Re: Scavenging one nearly new battery to make another?

Post by john61ct » Mar 26 2019 4:45pm

Note also that LiPo in general does not actually specify the chemistry, just that there is a polymer gel in the electrolyte (more mechanical construction aspect than chemical)

Most LiPo are lithium cobalt based, LiCoO2 specifically these days, but apparently NMC and combinations thereof also (used to) exist?

(someone please correct me if I'm wrong)

Each chemistry has their god / bad points, and may spec a higher or lower charge voltage.

RC LiPo just means no BMS cutout, and light as possible, which means thinner, weaker casing more fragile, like pouches as opposed to bulkier / heavier (and more robust) prismatic casing.

The A123 LFP cells are an exception, I believe no polymer in those, completely different chemistry and charge setpoints, C-rate vs thermal profile, etc.



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Re: Scavenging one nearly new battery to make another?

Post by Hillhater » Mar 26 2019 5:48pm

john61ct wrote:
Mar 26 2019 4:45pm
.
RC LiPo just means no BMS cutout, and light as possible, which means thinner, weaker casing more fragile, like pouches as opposed to bulkier / heavier (and more robust) prismatic casing.
Dont forget , RC lipo also has generally a much higher "C" rate.. (Power density =discharge power)..than other lithium batteries,
.....and IS available in heavier , robust, prismatic casing. !
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Re: Scavenging one nearly new battery to make another?

Post by mammonista » Mar 26 2019 7:55pm

Okay, according to the 'book' Toll says, "NO" on RC Lipo and he's not a big fan of LiCoO2 either. Not the safest batteries out there?
And I realize no Lithium based battery is completely safe. But in 18650, NMC and NCRs are readily available.
So which is it? Which is the preferred of those two chemistries is most favored here.
AND I'M NOT DOING LIPO!!! AND THE BATTERY IS GOING IN THE TRIANGLE! :-)

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