New 14s battery pack, US18650VTC6 vs NCR18650GA

Average DoD% is a **hugely** significant longevity factor. Do **not** discount the impact of this factor, that "avg DoD vs cycle lifetime" graph's curve may have different slope ratios, but has a similar shape with **every** chemistry afaik.

But only cycling to 50% while common in lead circles, is just whacko, hardly ever heard of anyone doing that with any version of lithium, and especially not in propulsion use cases.

Carrying around 80% more weight spending 80% more money, to get the same range, just does not make much sense for most users.

Certainly, always going to 80-90% DoD every trip, compared to only occasionally, averaging say 65-75% instead, I think is a reasonable longevity-extending strategy.

But then these aren't hard lines, greyscale all the way, your rig your choice.

C-rate is another biggie, 0.5C is healthier than 1C, 3C is healthier than 5C, especially the longer the bursts.

But the use case often dictates, may not really be able to bring that down much, just like trying to get shallower cycling, the size/weight penalty is too great for the desired performance.

Same of course with charging. Personally I consider 1C to be abusive, but for many long-distance or racing contexts, everyone wants as fast as possible charging long as things don't ignite. . .

Ambient temperature is similar, cool climate can mean triple or greater lifetimes compared to living in the tropics.

But fancy engineered TMSs are rare in the DIY world, few users dedicate fridge space to storing their packs. . .

eMark said:

john61ct said:

Vruzend no longer relies on "friction fit", as of v2.1

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V2.1 is still a "friction fit" as was its predecessor the V1.6 kit which has 12 compression barrel bolts. The V2.1 kit only has 8 compression barrel bolts, but each is suitable in the right hands for its suited application.

john61ct said:

With the addition of the through-bolts, maintaining connector pressure against the cell ends no longer **relies** on friction alone.

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Whether a Nishi kit or Vruzend kit they both rely on a "friction fit" in that the buss bars are not spot-welded to the cell ends. Both the V1.6 and V2.1 rely on the buss bars being held in place with screw terminal nuts (friction fit) as well as the barrel bolt tightening screws. One disadvantage of these Vruzend kits is being restricted to a [larger] rectangle (with space between the cells) as opposed to a smaller pack of staggered spot-welded cells with the option of other shapes (e.g. bottle, triangle, etc.)

You sound like you're promoting the V2.1 (?shilling?) with your "no longer relies on 'friction fit' " giving the wrong impression to newbies. It's not that the V2.1 doesn't have it's place/applicaton as a beginner DIY build by a novice and/or for experimenting by a more advance builder or for use as a variable powerwall. Whether a Nishi kit or a Vruzend kit they definitely have a place and offer an advantage for certain applications. They are a "friction fit" kit, but that is not a bad thing anymore than it is a good thing.

Peace!

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There's nothing wrong with a "friction" contact connection if it's kept clean and has sufficient pressure. I am in my 8th month of using a V2.1 on a 14s7p of PF cells and I couldn't be more satisfied with the performance of it so far. I've checked for loose bolts, nuts, corrosion ,voltage drops, and cracks every other week since I built it and nothing of issue so far. I wouldn't use one on a mountain bike jumping hills, but for a rack mounted setup on a commuter or scooter, I'd recommend any day.

999zip999 said:

1C would be hard to live with.

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1C continous is not that hard. peaks can be higher but a decently sized pack can comfortably be under .5C or even lower.

flippy said:

so if you want a pack that lasts for a decade or more you need to build it with 2900mAh cells and keep under 1C discharge peaks. if you do that you will basically never wear it out. fun fact: 2900mAh is also considerably cheaper then GA's.

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At first thought flippy meant to charge (for example M36 3450mAh) to no more than 84% of it's rated capacity being 2900mAh. Then taking a closer look at his wording i realized it wasn't a typo (or whatever). Wouldn't that mean that 84% charge (say around 4V) of a 2900mAh cell is only a cell capacity of 2436mAh. Wouldn't that mean the elapsed time with an 80% charge to 50% discharge daily routine would be less (shorter accumulated mileage) with an 8P14S 2900mAh (PF 10A cell rating) pack than with an 8P14S 3450mAh (M36 5A cell rating) pack ... right or wrong ??

Logic would seem to say that the more the capacity (i.e. M36) the better as long as you don't charge above 4.05-7V (depending on chemistry and condition of cell-- i guess ?).

As always there are trade-offs. Logic would still seem to say that a LG M36 has an advantage over a Panasonic PF. Wondering if what flippy was getting at with his 2900mAh battery is that how many cells in parallel is the deciding factor. For example wouldn't an 8P14S M36 pack still offer a slightly extended advantage in its cycle life ... compared to a 7P14S Panasonic PF pack's cycle life ? In this 8P vs 7P comparison consider all variables equal such as an average 2-4 amp draw, terrain and same accumulated mileage each day, etc the same.

This 14S thread discussion raises questions that aren't easily answered. For example which would be better over the long haul under the same conditions ... an 8P14S pack of Panasonic NCR18650G 3550mAh 8A rated cells or an 8P14S pack of LG M36 3450mAh 5A rated cells ?? Does it boil down to what your bank account (or wife) can afford/allow and one's personal preference (e.g. should i buy a Toyota or a Honda?)

EDIT Update:

john61ct said:

Certainly, always going to 80-90% DoD every trip, compared to only occasionally, averaging say 65-75% instead, I think is a reasonable longevity-extending strategy.

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My previous logic 80% charge and 75% discharge seems intact and even further expanded by john to 80-90% DoD. Soooo, in the above where is says "elapsed time with an 80% charge to 50% discharge" let's consider at least 75-80% discharge. So, a more realistic ebiking norm would seem to be 80% charge and 80% discharge.

So, as far as the above comparative cell examples we have now just included another variable. That being a 80% charge to 50% discharge routine VERSUS a 80% charge to 80% discharge routine as far as which routine has the greater cycle life all other daily riding factors equal ??

the problem is that high capcaity cells have poor lifecycles and quite wear sensitive. so they take abuse a LOT less kind then the lower capacity cells.
bigger cells are also MUCH more expensive then the 2900's, those currently have the best price per watt ratio so its simply cheaper to build a bigger pack with smaller cells then it is to have a smaller pack with high cpaicty cells that wear out a lot faster.

doing a 60% charge on a big cell is a possibility but it is still a stupid one as you are still stuck to the shitty discharge ratings high capaicty cells have.

do the math yourself with a fixed budget. the 2900's will yield the biggest battery with the highest current ratings.

flippy said:

doing a 60% charge on a big cell is a possibility but it is still a stupid one as you are still stuck to the shitty discharge ratings high capaicty cells have.

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Who in their right mind has ever suggested doing a 60% charge on an ES battery pack thread that you felt it relevant to mention in this 14S thread? Was it(60% charge) a typo mistake that you took to heart ?

Apparently you've decided not to answer any of the comparative questions in my above post although you are certainly qualified to do so. Do you not consider them relevant to this 7-8P14S thread? WHY you decided to mention "a 60% charge" seems irrelevant to the current 80% charge to 50% DoD vs 80% to 80% DoD (john's suggestion) as relative to a LG M36 3450mAh 7-8P14S pack VS a Panasonic 2900mAh 7-8P14S pack with respect to getting the longest-most extended cycle life from these two 7-8P14S packs.

In response to another recent post about the use of up to 5 Vruzend V2.1 kits (8P14S) i contend that they are a "friction fit" especially considering the pack's size mounted on Erik's bike for winter riding. Even moreso considering the intended use over Viking winter terrain with frigid temps and then brought inside again at work and then again brought inside when back home. Also, such a big pack mounted on an ebike susceptible to Viking terrain vibration (it's not Kansas-like terrain). It's my opinion (which has merit) that the V2.1 is designed more as a beginner DIY build with only enough pieces in a V2.1 kit for a typical 3P10S 36V build (e.g. scooter). IMO, Micah would be shaking in his shoes (if he knew) that Erik was mounting a 7-8P14S Vruzend pack (4-5 V2.1 kits combined) on his Viking bike for winter use. My Vruzend V1.6 kit won't be any larger than 4P10S and then seated comfortably in a storage compartment inside a larger storage trunk between the rear wheels of my etrike.

yes, the 60% is a typo it seems. you need to chill in your responses.

you came up with the argument about using high capacity cells and just keep lower SoC, and its not a viable option as you need to spend MORE money to get a pack that preforms worse then when using a more durable capacity like 2900.
with 2900 cells you can simply compensate the lower capacity by buying more cells. it increases power delivery (aka: reduces wear) and you get better performance for less money.

@eMark you are interpreting wrong meanings from the last posts from both me and @flippy.


> So, a more realistic ebiking norm would seem to be 80% charge and 80% discharge.

I was **not** advocating **any** charging profile based on SoC, that approach is not useful, as I clearly stated, stop twisting my words. Stopping at 80% is not a "norm", and would be stupid.

Use voltage/endAmps, and again, it's not as important whether your "working Full" is 4.05 or 4.1V, as how long you let the pack sit there.

But yes, shallower cycling will **always** give longer life everything being equal.

And, if you know you only need 20% of your capacity, then don't fill up all the way, cycling between 60-40% is better than 80-60%

_______
Flippy's general meaning, and I stated it clearly was that generally cells with high energy density do not last as long.

So given two models the same physical size, the one rated 2900mAh will be more robust than one rated 3200mAh. These are just examples.

Nothing to do with how high up the voltage / SoC curve you charge them, independent of any of the usage/care factors under the owner's control.

84% is just pulled out of, erm, thin air

Averaging 50% DoD is IMO also dumb. Nothing you're talking about has anything to do with "norms", mostly your misinterpretations, passed off as some "fantasy consensus". Stop that.

> the more the capacity (i.e. M36) the better

no, the opposite - you can't optimize for energy density and longevity, they are opposed. Just talking about **chemistry** performance.

Only charging to 4.05V is a separate idea, like the other usage/care factors under the owner's control, helping extend longevity within the cell chemistry's limitations.

7V is not a thing, dunno where you pulled that from.

Same with reducing C-rate by adding P's, Ah capacity, good design for longevity, but eventually pack is just too big & heavy.

eMark said:

For example which would be better over the long haul under the same conditions ... an 8P14S pack of Panasonic NCR18650G 3550mAh 8A rated cells or an 8P14S pack of LG M36 3450mAh 5A rated cells ?

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Define "better".

C-rate / power density, or
energy density, or
longevity

?

You can't optimise all three, much less price per Ah as well.

999zip999 said:

I'm 61 and my street bike goes 47mph on flats and 36mph on most hills. 7,000 watts. Funny I don't feel old yet.

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Wait until you fall, then you'll feel old !!!!

Jokes aside, I guess your are not peddling to much at these speeds.
In that case your'e having a motorbike competing with gas bikes.

Honk said:

999zip999 said:

I'm 61 and my street bike goes 47mph on flats and 36mph on most hills. 7,000 watts. Funny I don't feel old yet.

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Wait until you fall, then you'll feel old !!!!

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if you fall at 47mph you will feel a lot of things, just not your skin.

flippy said:

the problem is that high capcaity cells have poor lifecycles and quite wear sensitive. so they take abuse a LOT less kind then the lower capacity cells.
bigger cells are also MUCH more expensive then the 2900's, those currently have the best price per watt ratio so its simply cheaper to build a bigger pack with smaller cells then it is to have a smaller pack with high cpaicty cells that wear out a lot faster.

doing a 60% charge on a big cell is a possibility but it is still a stupid one as you are still stuck to the shitty discharge ratings high capaicty cells have.

do the math yourself with a fixed budget. the 2900's will yield the biggest battery with the highest current ratings.

Click to expand...

At nkon MJ1 is only 50 cents higher than the 29E. I wouldn't call that "MUCH" higher than the HE cell, and when you need a small pack to go for as long as possible - a measly 30% higher cost does justify the higher capacity.

Theory that 2900 mAh cells are better than high capacity/energy cells is not always true. Look how inferior is PF compare to M36 :





Edit :

Price comparison for 100 cells at nkon (EUR)
PF ……. 255 EUR
29E7 … 242 EUR
M36 …. 299 EUR
MJ1 ....295 EUR


Price comparison per Ah
PF …..2 800 mAh 0,91 EUR/Ah
29E7 ….. 2 800 mAh 0,86 EUR/Ah
M36 …… 3 300 mAh 0,91 EUR/Ah
MJ1 ....3 300 mAh 0,89 EUR/Ah

PF and M36 price per Ah is the same.
Price difference 29E7 v M36 (MJ1) per Ah is 5 EUR (MJ1 3 EUR) for 100pcs battery pack. The same capacity 29E7 battery pack will cost 5 EUR (3 EUR MJ1) less and will be much heavier and bigger than M36 or MJ1 pack.

it depends on battery size, but 50 bucks on a 100 cell pack is a lot for most people considering the target audience here, especially if you take the E6 version, those are even cheaper and preform basically indentically.

its nice to see pricing to have changed, but the main advantage of using more but smaller cells is still the higher specs you get and the less wear per cell. spreading the load over more P strings is more beneficial then just grabbing the highest capacties and least amounts of cells.

yes, a pack will be bigger when restricted by a fixed budget, but it will also preform better and last longer, and cost less.

Well, let´s look at the facts from different perspective :

A ) battery size and weight is the most important factor for ebike

B) cells price is only part of the total battery price

C) Panasonic PF 2 900 mAh lifetime is inferior to M36 and MJ1, price per Ah is the same, unfortunately we have to cancel this option as not bargain.

D) Samsung 29E price advantage is becaming rather pale if we realize options :

1) If we use more cells to have the same capacity as M36 and spread the load, than the price advantage disappears, and arrive in penalty of weight and size. Moreover it is not clear how better (if ever) lifetime we can expect in such case, we have no data.
2) If we use the same amount of the cells, 29E pack DOD will be higher and capacity smaller than M36 pack. Lifetime may be worse, but we again have no data.

Your last sentence is giving no sense if you read it attentively.

docware said:

Well, let´s look at the facts from different perspective :

A ) battery size and weight is the most important factor for ebike

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Thanks for your graphs and accompanying informative posts ... :thumb:

It's certainly understandable that a DIY ebiker would consider the price savings of a Vruzend 7-8P14S M36 pack using 4-5 V2.1 Vruzend kits. This approach does allow Erik to experiment with different pack configurations as a 8P14S conventional Vruzend pack arrangement measures approx 4" x 8" x 13" when taking into account just the BMS, foam wrap and shrink tube.

Erik possibly decided to break his Vruzend DIY into two Vruzend packs with one 4P14S up front in the frame and a 3P14S cojoined on a rack above the rear wheel? The Vruzend kits offer interesting possibilities for hands-on DIY guys that enjoy the satistaction of doing their own build with practical simplicity (KIS), cost savingss, maintenance advantages and as always SAFETY as NUMMER EN.

EDIT: at first had 3P pack up front and 4P pack at rear, but decided to change it to 4P in frame and 3P on rack. Third edit decided that it's more practical to have one 4" x 8" x 13" pack comfortably situaled in frame and rack for other essentials. Would be helpful if Erik uploads a photo once he's satisfied with final situaton.

If LG M29 is really as good as Pajda declares, than with its price 217 EUR/ 100 pcs is this new kid in the town obvious favorit of 2 900 mAh class.

flippy said:

anything with higher capacity will die faster.

note: the PF does have much better lifespan when the loads are reasonable. the 29E can just take more abuse in my tests.
if you have a sub 1C discharge and stop at 4.05V then the PF will outlast the 29E by far.

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Sometimes, it's useful to repost a previous post. Me thinks it may be time to repost flippy's previous "note:" The thing is deciding what is a "reasonable" service life to your ebiking routine.

For my etriking the Panasonic 2900mAh PF should be a better choice than the M36 for my easy-going routine. However, for Erik's ebiking routine the M36 looks to be an excellent choice; especially when considering docware's DCIR ageing cycle test graph ... https://endless-sphere.com/forums/download/file.php?id=261801.

My etrike allows me to cushion carry (protect) my DIY Vruzend pack in the rear trunk over and between the 16" rear wheels. Thus, it may make more sense to build a 6P10S 36V pack if i had more faith in a Vruzend "friction-fit" build. Still considering ways to build my Vruzend pack LESS of a friction-fit

The advantage of a Vruzend V2.1 kit(s) is easily disassembling and using again if and when advanced chemistry batteries are available and/or when the cycle life of your first V2.1 DIY pack build is disfunctional. Of course that's assuming the new improved batteries are the same diameter as the current 18650's.

PS: Would be helpful to know (from those in the KNOW), if the Panasonic 2900mAh 10A cell is a better cell choice than the Samsung 3000mAh 15A cell for my easy-going etriking routine (price difference aside)?

Erik wants his 14S LG M36 pack to experience a long healthy life. As a general rule it was my understanding that it's better to go with an 80% charge and 50% discharge than an 80% charge and 80% discharge? Maybe, for some an 80% charge and 65% discharge is the happy medium that best suits one's daily ebiking routine. Here's a real-life scenario that may be similar to Erik's daily ebiking routine with two possible options being 80/50 or 80/80 ...

• 1) 80% charge to work results in a 50% discharge ... then while at work charge to 80% and 50% discharge when back home.

• 2) 80% charge to work and then back home again resulting in an 80% discharge of a 7-8P14S LG M36 pack.

Any consensus on which routine is favored for getting the most cycles for extending the longevity of Erik's 7-8P14S M36 pack ?
Maybe 80/35 is a good midde-of-the-road routine when possible. However, like Erik some of us ebiking commuters are undecided between an 80/50 two times a day or an 80/20 once a day when it comes to gettng the most cycle life out of a pack. The following graph implies 3.3V is the low end discharge cut-off for ebiking -- https://ibikes.files.wordpress.com/2017/04/41.png?w=768

https://www.batteryuniversity.com/_img/content/18650chargeDischarge-web.jpg
According to the above chart the impression is given that a 18650 cell shouldn't be discharged below 3.0V. Wouldn't this be good advice for both the PanasonicPF 2900mAh 10A cell as well as the LG M36 3450mAh 5A cell with similar daily ebiking routines for cycle life longevity?

According to docware's chart for LP M36 charged to 80% is 4.00V, 50% discharge is 3.70V, and 80% discharge is 3.47V with 0% being 3.03V. 0% being the low end 18650 cell voltage when striving for cycle life longevity -- right or wrong ?
https://endless-sphere.com/forums/download/file.php?id=261831

EDIT Correction: Meant to say 65% discharge instead of original post of 35% discharge :?

eMark said:

Erik possibly decided to break his Vruzend DIY into two Vruzend packs with one 4P14S up front in the frame and a 3P14S cojoined on a rack above the rear wheel?

Would be helpful if Erik uploads a photo once he's satisfied with final situaton.

Click to expand...

I went with a triangular battery that fit inside the frame. I've put on a 25W heater on the lower part of the battery, and a temperature probe in the middle of the pack. No heat shrink, but a protective rubber mat is covering the entire pack. Some insulation added on the sides.
The controller will be moved to the lower front of the triangle frame later, but is temporary just mounted on top of the frame.

Definitely need to send that layout diagram to Micah. I'll PM you his Florida address.
Your 8P14S LG M36 well-designed DIY pack is deserving of a Vruzend V2.1 Nobel Prize ... 8) :thumb:

eMark said:

Erik wants his 8P14S LG M36 pack to experience a long healthy life. As a general rule it was my understanding that it's better to go with an 80% charge and 50% discharge than an 80% charge and 80% discharge? Maybe, for some an 80% charge and 65% discharge is the happy medium that best suits one's daily ebiking routine. Here's a real-life scenario that may be similar to Erik's daily ebiking routine with two possible options being 80/50 or 80/80 ...

• 1) 80% charge to work results in a 50% discharge ... then while at work charge to 80% and 50% discharge when back home.

• 2) 80% charge to work and then back home again resulting in an 80% discharge of a 8P14S LG M36 pack.

Any consensus on which routine is favored for getting the most cycles for extending the longevity of Erik's 8P14S M36 pack ?
Maybe 80/65 is a good midde-of-the-road routine when possible. However, like Erik some of us ebiking commuters are undecided between an 80/50 two times a day or an 80/20 once a day when it comes to gettng the most cycle life out of a pack. The following graph implies 3.3V is the low end discharge cut-off for ebiking -- https://ibikes.files.wordpress.com/2017/04/41.png?w=768

https://www.batteryuniversity.com/_img/content/18650chargeDischarge-web.jpg
According to the above chart the impression is given that a 18650 cell shouldn't be discharged below 3.0V. Wouldn't this be good advice for both the PanasonicPF 2900mAh 10A cell as well as the LG M36 3450mAh 5A cell with similar daily ebiking routines for cycle life longevity?

According to docware's chart for LP M36 charged to 80% is 4.00V, 50% discharge is 3.70V, and 80% discharge is 3.47V with 0% being 3.03V. For docware's purpose 0% being the low end 18650 cell voltage (striving for cycle life longevity) -- right or wrong ?
https://endless-sphere.com/forums/download/file.php?id=261831

Click to expand...

EDIT correction: Meant to say 65% discharge instead of 35% discharge in previous post :?

That's a nice giant pack! Are you relying on only two bus bars to handle all of the current for some of the serial connections?

Yes, but where it is only two bus bars i've made them at least double. No connections got hot during load test (constant ~2000W load over some time).

Excellent. Let us know what your range turns out to be eventually I consider my 14s6p MJ1 packs to be 40 miles at 15-20mph, 20 miles at 30-35mph, and a bit more when used on the recumbent.